Refactor.

Bumps [actions/attest-build-provenance](https://github.com/actions/attest-build-provenance) from 1 to 2.
- [Release notes](https://github.com/actions/attest-build-provenance/releases)
- [Changelog](https://github.com/actions/attest-build-provenance/blob/main/RELEASE.md)
- [Commits](https://github.com/actions/attest-build-provenance/compare/v1...v2)

---
updated-dependencies:
- dependency-name: actions/attest-build-provenance
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/actions/vmactions/template.yml

@@ -0,0 +1,16 @@
+name: VM Actions matrix
+description: VM Actions matrix template
+
+inputs:
+  run:
+    description: The CI command to run
+    required: true
+
+runs:
+  using: composite
+  steps:
+    - uses: ${VMACTIONS}
+      with:
+        usesh: true
+        copyback: false
+        run: ${{inputs.run}}

.github/workflows/build-test.sh

@@ -8,4 +8,8 @@ for p in $(go list ./...); do
   name="$(basename "$p").test"
   (cd ${dir}; go test -c ${BUILDFLAGS:-})
   [ -f "${dir}/${name}" ] && echo "(cd ${dir}; ./${name} ${TESTFLAGS:-})" >> test.sh
-done
+done
+
+if [[ -v VMACTIONS ]]; then
+  envsubst < .github/actions/vmactions/template.yml > .github/actions/vmactions/action.yml
+fi

.github/workflows/cross.sh

@@ -18,12 +18,8 @@ echo js            ; GOOS=js        GOARCH=wasm  go build .
 echo wasip1        ; GOOS=wasip1    GOARCH=wasm  go build .
 echo linux-flock   ; GOOS=linux     GOARCH=amd64 go build -tags sqlite3_flock .
 echo linux-dotlk   ; GOOS=linux     GOARCH=amd64 go build -tags sqlite3_dotlk .
-echo linux-nosys   ; GOOS=linux     GOARCH=amd64 go build -tags sqlite3_nosys .
 echo darwin-flock  ; GOOS=darwin    GOARCH=amd64 go build -tags sqlite3_flock .
 echo darwin-dotlk  ; GOOS=darwin    GOARCH=amd64 go build -tags sqlite3_dotlk .
-echo darwin-nosys  ; GOOS=darwin    GOARCH=amd64 go build -tags sqlite3_nosys .
 echo windows-dotlk ; GOOS=windows   GOARCH=amd64 go build -tags sqlite3_dotlk .
-echo windows-nosys ; GOOS=windows   GOARCH=amd64 go build -tags sqlite3_nosys .
 echo freebsd-dotlk ; GOOS=freebsd   GOARCH=amd64 go build -tags sqlite3_dotlk .
-echo freebsd-nosys ; GOOS=freebsd   GOARCH=amd64 go build -tags sqlite3_nosys .
 echo solaris-dotlk ; GOOS=solaris   GOARCH=amd64 go build -tags sqlite3_dotlk .

.github/workflows/repro.sh

@@ -2,14 +2,14 @@
 set -euo pipefail
 
 if [[ "$OSTYPE" == "linux"* ]]; then
-  WASI_SDK="https://github.com/WebAssembly/wasi-sdk/releases/download/wasi-sdk-24/wasi-sdk-24.0-x86_64-linux.tar.gz"
-  BINARYEN="https://github.com/WebAssembly/binaryen/releases/download/version_120/binaryen-version_120-x86_64-linux.tar.gz"
+  WASI_SDK="https://github.com/WebAssembly/wasi-sdk/releases/download/wasi-sdk-25/wasi-sdk-25.0-x86_64-linux.tar.gz"
+  BINARYEN="https://github.com/WebAssembly/binaryen/releases/download/version_121/binaryen-version_121-x86_64-linux.tar.gz"
 elif [[ "$OSTYPE" == "darwin"* ]]; then
-  WASI_SDK="https://github.com/WebAssembly/wasi-sdk/releases/download/wasi-sdk-24/wasi-sdk-24.0-x86_64-macos.tar.gz"
-  BINARYEN="https://github.com/WebAssembly/binaryen/releases/download/version_120/binaryen-version_120-arm64-macos.tar.gz"
+  WASI_SDK="https://github.com/WebAssembly/wasi-sdk/releases/download/wasi-sdk-25/wasi-sdk-25.0-arm64-macos.tar.gz"
+  BINARYEN="https://github.com/WebAssembly/binaryen/releases/download/version_121/binaryen-version_121-arm64-macos.tar.gz"
 elif [[ "$OSTYPE" == "msys" || "$OSTYPE" == "cygwin" ]]; then
-  WASI_SDK="https://github.com/WebAssembly/wasi-sdk/releases/download/wasi-sdk-24/wasi-sdk-24.0-x86_64-windows.tar.gz"
-  BINARYEN="https://github.com/WebAssembly/binaryen/releases/download/version_120/binaryen-version_120-x86_64-windows.tar.gz"
+  WASI_SDK="https://github.com/WebAssembly/wasi-sdk/releases/download/wasi-sdk-25/wasi-sdk-25.0-x86_64-windows.tar.gz"
+  BINARYEN="https://github.com/WebAssembly/binaryen/releases/download/version_121/binaryen-version_121-x86_64-windows.tar.gz"
 fi
 
 # Download tools

.github/workflows/repro.yml

@@ -18,14 +18,12 @@ jobs:
     steps:
     - uses: ilammy/msvc-dev-cmd@v1
     - uses: actions/checkout@v4
-    - uses: actions/setup-go@v5
-      with: { go-version: stable }
 
     - name: Build
       shell: bash
       run: .github/workflows/repro.sh
 
-    - uses: actions/attest-build-provenance@v1
+    - uses: actions/attest-build-provenance@v2
       if: matrix.os == 'ubuntu-latest'
       with:
         subject-path: |

.github/workflows/test.yml

@@ -5,12 +5,14 @@ on:
     branches: [ "main" ]
     paths:
       - '**.go'
+      - '**.mod'
       - '**.wasm'
       - '**.wasm.bz2'
   pull_request:
     branches: [ "main" ]
     paths:
       - '**.go'
+      - '**.mod'
       - '**.wasm'
       - '**.wasm.bz2'
   workflow_dispatch:
@@ -52,10 +54,6 @@ jobs:
     - name: Test
       run: go test -v ./... -bench . -benchtime=1x
 
-    - name: Test no locks
-      run: go test -v -tags sqlite3_nosys ./...
-      if: matrix.os == 'ubuntu-latest'
-
     - name: Test BSD locks
       run: go test -v -tags sqlite3_flock ./...
       if: matrix.os == 'macos-latest'
@@ -83,41 +81,24 @@ jobs:
         github.event_name == 'push' &&
         matrix.os == 'ubuntu-latest'
 
-  test-intel:
-    runs-on: macos-13
-    needs: test
-
-    steps:
-    - uses: actions/checkout@v4
-    - uses: actions/setup-go@v5
-      with: { go-version: stable }
-
-    - name: Git LFS pull
-      uses: ./.github/actions/lfs
-
-    - name: Test
-      run: go test -v ./...
-
   test-bsd:
     strategy:
       matrix:
         os:
           - name: freebsd
-            version: '14.1'
+            version: '14.2'
             flags: '-test.v'
-          - name: openbsd
-            version: '7.5'
-            flags: '-test.v -test.short'
           - name: netbsd
             version: '10.0'
+            flags: '-test.v'
+          - name: openbsd
+            version: '7.6'
             flags: '-test.v -test.short'
     runs-on: ubuntu-latest
     needs: test
 
     steps:
     - uses: actions/checkout@v4
-    - uses: actions/setup-go@v5
-      with: { go-version: stable }
 
     - name: Git LFS pull
       uses: ./.github/actions/lfs
@@ -129,7 +110,7 @@ jobs:
       run: .github/workflows/build-test.sh
 
     - name: Test
-      uses: cross-platform-actions/action@v0.25.0
+      uses: cross-platform-actions/action@v0.26.0
       with:
         operating_system: ${{ matrix.os.name }}
         version: ${{ matrix.os.version }}
@@ -137,6 +118,44 @@ jobs:
         run: . ./test.sh
         sync_files: runner-to-vm
 
+  test-vm:
+    strategy:
+      matrix:
+        os:
+          - name: dragonfly
+            action: 'vmactions/dragonflybsd-vm@v1'
+            tflags: '-test.v'
+          - name: illumos
+            action: 'vmactions/omnios-vm@v1'
+            tflags: '-test.v'
+          - name: solaris
+            action: 'vmactions/solaris-vm@v1'
+            bflags: '-tags sqlite3_dotlk'
+            tflags: '-test.v'
+    runs-on: ubuntu-latest
+    needs: test
+
+    steps:
+    - uses: actions/checkout@v4
+
+    - name: Git LFS pull
+      uses: ./.github/actions/lfs
+
+    - name: Build
+      env:
+        GOOS: ${{ matrix.os.name }}
+        BUILDFLAGS: ${{ matrix.os.bflags }}
+        TESTFLAGS:  ${{ matrix.os.tflags }}
+        VMACTIONS:  ${{ matrix.os.action }}
+      run: .github/workflows/build-test.sh
+
+    - name: Test
+      uses: ./.github/actions/vmactions
+      with:
+        usesh: true
+        copyback: false
+        run: . ./test.sh
+
   test-qemu:
     runs-on: ubuntu-latest
     needs: test
@@ -165,8 +184,8 @@ jobs:
     - name: Test s390x (big-endian)
       run: GOARCH=s390x go test -v -short -tags sqlite3_dotlk ./...
 
-  test-vm:
-    runs-on: ubuntu-latest
+  test-macintel:
+    runs-on: macos-13
     needs: test
 
     steps:
@@ -177,30 +196,5 @@ jobs:
     - name: Git LFS pull
       uses: ./.github/actions/lfs
 
-    - name: Build illumos
-      env:
-        GOOS: illumos
-        TESTFLAGS: '-test.v -test.short'
-      run: .github/workflows/build-test.sh
-
-    - name: Test illumos
-      uses: vmactions/omnios-vm@v1
-      with:
-        usesh: true
-        copyback: false
-        run: . ./test.sh
-
-    - name: Build Solaris
-      env:
-        GOOS: solaris
-        TESTFLAGS: '-test.v -test.short'
-        BUILDFLAGS: '-tags sqlite3_dotlk'
-      run: .github/workflows/build-test.sh
-
-    - name: Test Solaris
-      uses: vmactions/solaris-vm@v1
-      with:
-        usesh: true
-        copyback: false
-        run: . ./test.sh
-      continue-on-error: true
+    - name: Test
+      run: go test -v ./...

README.md

@@ -10,7 +10,7 @@ as well as direct access to most of the [C SQLite API](https://sqlite.org/cintro
 
 It wraps a [Wasm](https://webassembly.org/) [build](embed/) of SQLite,
 and uses [wazero](https://wazero.io/) as the runtime.\
-Go, wazero and [`x/sys`](https://pkg.go.dev/golang.org/x/sys) are the _only_ runtime dependencies.
+Go, wazero and [`x/sys`](https://pkg.go.dev/golang.org/x/sys) are the _only_ direct dependencies.
 
 ### Getting started
 
@@ -74,10 +74,10 @@ This project aims for [high test coverage](https://github.com/ncruces/go-sqlite3
 It also benefits greatly from [SQLite's](https://sqlite.org/testing.html) and
 [wazero's](https://tetrate.io/blog/introducing-wazero-from-tetrate/#:~:text=Rock%2Dsolid%20test%20approach) thorough testing.
 
-Every commit is [tested](https://github.com/ncruces/go-sqlite3/wiki/Test-matrix) on
+Every commit is [tested](https://github.com/ncruces/go-sqlite3/wiki/Support-matrix) on
 Linux (amd64/arm64/386/riscv64/ppc64le/s390x), macOS (amd64/arm64),
 Windows (amd64), FreeBSD (amd64), OpenBSD (amd64), NetBSD (amd64),
-illumos (amd64), and Solaris (amd64).
+DragonFly BSD (amd64), illumos (amd64), and Solaris (amd64).
 
 The Go VFS is tested by running SQLite's
 [mptest](https://github.com/sqlite/sqlite/blob/master/mptest/mptest.c).
@@ -90,9 +90,20 @@ Perfomance of the [`database/sql`](https://pkg.go.dev/database/sql) driver is
 The Wasm and VFS layers are also tested by running SQLite's
 [speedtest1](https://github.com/sqlite/sqlite/blob/master/test/speedtest1.c).
 
+### FAQ, issues, new features
+
+For questions, please see [Discussions](https://github.com/ncruces/go-sqlite3/discussions/categories/q-a).
+
+Also, post there if you used this driver for something interesting
+([_"Show and tell"_](https://github.com/ncruces/go-sqlite3/discussions/categories/show-and-tell)),
+have an [idea](https://github.com/ncruces/go-sqlite3/discussions/categories/ideas)…
+
+The [Issue](https://github.com/ncruces/go-sqlite3/issues) tracker is for bugs we want fixed,
+and features we're working on, planning to work on, or asking for help with.
+
 ### Alternatives
 
 - [`modernc.org/sqlite`](https://pkg.go.dev/modernc.org/sqlite)
 - [`crawshaw.io/sqlite`](https://pkg.go.dev/crawshaw.io/sqlite)
 - [`github.com/mattn/go-sqlite3`](https://pkg.go.dev/github.com/mattn/go-sqlite3)
-- [`github.com/zombiezen/go-sqlite`](https://pkg.go.dev/github.com/zombiezen/go-sqlite)
+- [`github.com/zombiezen/go-sqlite`](https://pkg.go.dev/github.com/zombiezen/go-sqlite)

conn.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"fmt"
 	"math"
+	"math/rand"
 	"net/url"
 	"strings"
 	"time"
@@ -24,7 +25,6 @@ type Conn struct {
 	interrupt  context.Context
 	pending    *Stmt
 	stmts      []*Stmt
-	timer      *time.Timer
 	busy       func(context.Context, int) bool
 	log        func(xErrorCode, string)
 	collation  func(*Conn, string)
@@ -36,7 +36,9 @@ type Conn struct {
 	rollback   func()
 	arena      arena
 
-	handle uint32
+	busy1st time.Time
+	busylst time.Time
+	handle  uint32
 }
 
 // Open calls [OpenFlags] with [OPEN_READWRITE], [OPEN_CREATE] and [OPEN_URI].
@@ -389,38 +391,20 @@ func (c *Conn) BusyTimeout(timeout time.Duration) error {
 }
 
 func timeoutCallback(ctx context.Context, mod api.Module, count, tmout int32) (retry uint32) {
+	// https://fractaledmind.github.io/2024/04/15/sqlite-on-rails-the-how-and-why-of-optimal-performance/
 	if c, ok := ctx.Value(connKey{}).(*Conn); ok && c.interrupt.Err() == nil {
-		const delays = "\x01\x02\x05\x0a\x0f\x14\x19\x19\x19\x32\x32\x64"
-		const totals = "\x00\x01\x03\x08\x12\x21\x35\x4e\x67\x80\xb2\xe4"
-		const ndelay = int32(len(delays) - 1)
-
-		var delay, prior int32
-		if count <= ndelay {
-			delay = int32(delays[count])
-			prior = int32(totals[count])
-		} else {
-			delay = int32(delays[ndelay])
-			prior = int32(totals[ndelay]) + delay*(count-ndelay)
+		switch {
+		case count == 0:
+			c.busy1st = time.Now()
+		case time.Since(c.busy1st) >= time.Duration(tmout)*time.Millisecond:
+			return 0
 		}
-
-		if delay = min(delay, tmout-prior); delay > 0 {
-			delay := time.Duration(delay) * time.Millisecond
-			if c.interrupt.Done() == nil {
-				time.Sleep(delay)
-				return 1
-			}
-			if c.timer == nil {
-				c.timer = time.NewTimer(delay)
-			} else {
-				c.timer.Reset(delay)
-			}
-			select {
-			case <-c.interrupt.Done():
-				c.timer.Stop()
-			case <-c.timer.C:
-				return 1
-			}
+		if time.Since(c.busylst) < time.Millisecond {
+			const sleepIncrement = 2*1024*1024 - 1 // power of two, ~2ms
+			time.Sleep(time.Duration(rand.Int63() & sleepIncrement))
 		}
+		c.busylst = time.Now()
+		return 1
 	}
 	return 0
 }
@@ -501,8 +485,12 @@ func (c *Conn) TableColumnMetadata(schema, table, column string) (declType, coll
 		uint64(declTypePtr), uint64(collSeqPtr),
 		uint64(notNullPtr), uint64(primaryKeyPtr), uint64(autoIncPtr))
 	if err = c.error(r); err == nil && column != "" {
-		declType = util.ReadString(c.mod, util.ReadUint32(c.mod, declTypePtr), _MAX_NAME)
-		collSeq = util.ReadString(c.mod, util.ReadUint32(c.mod, collSeqPtr), _MAX_NAME)
+		if ptr := util.ReadUint32(c.mod, declTypePtr); ptr != 0 {
+			declType = util.ReadString(c.mod, ptr, _MAX_NAME)
+		}
+		if ptr := util.ReadUint32(c.mod, collSeqPtr); ptr != 0 {
+			collSeq = util.ReadString(c.mod, ptr, _MAX_NAME)
+		}
 		notNull = util.ReadUint32(c.mod, notNullPtr) != 0
 		autoInc = util.ReadUint32(c.mod, autoIncPtr) != 0
 		primaryKey = util.ReadUint32(c.mod, primaryKeyPtr) != 0

driver/driver.go

@@ -81,6 +81,7 @@ import (
 	"fmt"
 	"io"
 	"net/url"
+	"reflect"
 	"strings"
 	"time"
 	"unsafe"
@@ -107,17 +108,17 @@ func init() {
 // The second callback is called before the driver closes a connection.
 // The [sqlite3.Conn] can be used to execute queries, register functions, etc.
 func Open(dataSourceName string, fn ...func(*sqlite3.Conn) error) (*sql.DB, error) {
-	var drv SQLite
 	if len(fn) > 2 {
 		return nil, sqlite3.MISUSE
 	}
+	var init, term func(*sqlite3.Conn) error
 	if len(fn) > 1 {
-		drv.term = fn[1]
+		term = fn[1]
 	}
 	if len(fn) > 0 {
-		drv.init = fn[0]
+		init = fn[0]
 	}
-	c, err := drv.OpenConnector(dataSourceName)
+	c, err := newConnector(dataSourceName, init, term)
 	if err != nil {
 		return nil, err
 	}
@@ -125,10 +126,7 @@ func Open(dataSourceName string, fn ...func(*sqlite3.Conn) error) (*sql.DB, erro
 }
 
 // SQLite implements [database/sql/driver.Driver].
-type SQLite struct {
-	init func(*sqlite3.Conn) error
-	term func(*sqlite3.Conn) error
-}
+type SQLite struct{}
 
 var (
 	// Ensure these interfaces are implemented:
@@ -137,7 +135,7 @@ var (
 
 // Open implements [database/sql/driver.Driver].
 func (d *SQLite) Open(name string) (driver.Conn, error) {
-	c, err := d.newConnector(name)
+	c, err := newConnector(name, nil, nil)
 	if err != nil {
 		return nil, err
 	}
@@ -146,11 +144,11 @@ func (d *SQLite) Open(name string) (driver.Conn, error) {
 
 // OpenConnector implements [database/sql/driver.DriverContext].
 func (d *SQLite) OpenConnector(name string) (driver.Connector, error) {
-	return d.newConnector(name)
+	return newConnector(name, nil, nil)
 }
 
-func (d *SQLite) newConnector(name string) (*connector, error) {
-	c := connector{driver: d, name: name}
+func newConnector(name string, init, term func(*sqlite3.Conn) error) (*connector, error) {
+	c := connector{name: name, init: init, term: term}
 
 	var txlock, timefmt string
 	if strings.HasPrefix(name, "file:") {
@@ -190,7 +188,8 @@ func (d *SQLite) newConnector(name string) (*connector, error) {
 }
 
 type connector struct {
-	driver  *SQLite
+	init    func(*sqlite3.Conn) error
+	term    func(*sqlite3.Conn) error
 	name    string
 	txLock  string
 	tmRead  sqlite3.TimeFormat
@@ -199,7 +198,7 @@ type connector struct {
 }
 
 func (n *connector) Driver() driver.Driver {
-	return n.driver
+	return &SQLite{}
 }
 
 func (n *connector) Connect(ctx context.Context) (res driver.Conn, err error) {
@@ -228,13 +227,13 @@ func (n *connector) Connect(ctx context.Context) (res driver.Conn, err error) {
 			return nil, err
 		}
 	}
-	if n.driver.init != nil {
-		err = n.driver.init(c.Conn)
+	if n.init != nil {
+		err = n.init(c.Conn)
 		if err != nil {
 			return nil, err
 		}
 	}
-	if n.pragmas || n.driver.init != nil {
+	if n.pragmas || n.init != nil {
 		s, _, err := c.Conn.Prepare(`PRAGMA query_only`)
 		if err != nil {
 			return nil, err
@@ -250,9 +249,9 @@ func (n *connector) Connect(ctx context.Context) (res driver.Conn, err error) {
 			return nil, err
 		}
 	}
-	if n.driver.term != nil {
+	if n.term != nil {
 		err = c.Conn.Trace(sqlite3.TRACE_CLOSE, func(sqlite3.TraceEvent, any, any) error {
-			return n.driver.term(c.Conn)
+			return n.term(c.Conn)
 		})
 		if err != nil {
 			return nil, err
@@ -275,6 +274,7 @@ func (n *connector) Connect(ctx context.Context) (res driver.Conn, err error) {
 //	if err != nil {
 //		log.Fatal(err)
 //	}
+//	defer conn.Close()
 //
 //	err = conn.Raw(func(driverConn any) error {
 //		conn := driverConn.(driver.Conn)
@@ -288,6 +288,8 @@ func (n *connector) Connect(ctx context.Context) (res driver.Conn, err error) {
 type Conn interface {
 	Raw() *sqlite3.Conn
 	driver.Conn
+	driver.ConnBeginTx
+	driver.ConnPrepareContext
 }
 
 type conn struct {
@@ -301,10 +303,8 @@ type conn struct {
 
 var (
 	// Ensure these interfaces are implemented:
-	_ Conn                      = &conn{}
-	_ driver.ConnBeginTx        = &conn{}
-	_ driver.ConnPrepareContext = &conn{}
-	_ driver.ExecerContext      = &conn{}
+	_ Conn                 = &conn{}
+	_ driver.ExecerContext = &conn{}
 )
 
 func (c *conn) Raw() *sqlite3.Conn {
@@ -380,7 +380,7 @@ func (c *conn) PrepareContext(ctx context.Context, query string) (driver.Stmt, e
 	if err != nil {
 		return nil, err
 	}
-	if tail != "" {
+	if notWhitespace(tail) {
 		s.Close()
 		return nil, util.TailErr
 	}
@@ -581,8 +581,22 @@ type rows struct {
 	names []string
 	types []string
 	nulls []bool
+	scans []scantype
 }
 
+type scantype byte
+
+const (
+	_ANY  scantype = iota
+	_INT  scantype = scantype(sqlite3.INTEGER)
+	_REAL scantype = scantype(sqlite3.FLOAT)
+	_TEXT scantype = scantype(sqlite3.TEXT)
+	_BLOB scantype = scantype(sqlite3.BLOB)
+	_NULL scantype = scantype(sqlite3.NULL)
+	_BOOL scantype = iota
+	_TIME
+)
+
 var (
 	// Ensure these interfaces are implemented:
 	_ driver.RowsColumnTypeDatabaseTypeName = &rows{}
@@ -606,21 +620,42 @@ func (r *rows) Columns() []string {
 	return r.names
 }
 
-func (r *rows) loadTypes() {
+func (r *rows) loadColumnMetadata() {
 	if r.nulls == nil {
 		count := r.Stmt.ColumnCount()
 		nulls := make([]bool, count)
 		types := make([]string, count)
+		scans := make([]scantype, count)
 		for i := range nulls {
 			if col := r.Stmt.ColumnOriginName(i); col != "" {
 				types[i], _, nulls[i], _, _, _ = r.Stmt.Conn().TableColumnMetadata(
 					r.Stmt.ColumnDatabaseName(i),
 					r.Stmt.ColumnTableName(i),
 					col)
+				types[i] = strings.ToUpper(types[i])
+				// These types are only used before we have rows,
+				// and otherwise as type hints.
+				// The first few ensure STRICT tables are strictly typed.
+				// The other two are type hints for booleans and time.
+				switch types[i] {
+				case "INT", "INTEGER":
+					scans[i] = _INT
+				case "REAL":
+					scans[i] = _REAL
+				case "TEXT":
+					scans[i] = _TEXT
+				case "BLOB":
+					scans[i] = _BLOB
+				case "BOOLEAN":
+					scans[i] = _BOOL
+				case "DATE", "TIME", "DATETIME", "TIMESTAMP":
+					scans[i] = _TIME
+				}
 			}
 		}
 		r.nulls = nulls
 		r.types = types
+		r.scans = scans
 	}
 }
 
@@ -637,7 +672,7 @@ func (r *rows) declType(index int) string {
 }
 
 func (r *rows) ColumnTypeDatabaseTypeName(index int) string {
-	r.loadTypes()
+	r.loadColumnMetadata()
 	decltype := r.types[index]
 	if len := len(decltype); len > 0 && decltype[len-1] == ')' {
 		if i := strings.LastIndexByte(decltype, '('); i >= 0 {
@@ -648,13 +683,57 @@ func (r *rows) ColumnTypeDatabaseTypeName(index int) string {
 }
 
 func (r *rows) ColumnTypeNullable(index int) (nullable, ok bool) {
-	r.loadTypes()
+	r.loadColumnMetadata()
 	if r.nulls[index] {
 		return false, true
 	}
 	return true, false
 }
 
+func (r *rows) ColumnTypeScanType(index int) (typ reflect.Type) {
+	r.loadColumnMetadata()
+	scan := r.scans[index]
+
+	if r.Stmt.Busy() {
+		// SQLite is dynamically typed and we now have a row.
+		// Always use the type of the value itself,
+		// unless the scan type is more specific
+		// and can scan the actual value.
+		val := scantype(r.Stmt.ColumnType(index))
+		useValType := true
+		switch {
+		case scan == _TIME && val != _BLOB && val != _NULL:
+			t := r.Stmt.ColumnTime(index, r.tmRead)
+			useValType = t == time.Time{}
+		case scan == _BOOL && val == _INT:
+			i := r.Stmt.ColumnInt64(index)
+			useValType = i != 0 && i != 1
+		case scan == _BLOB && val == _NULL:
+			useValType = false
+		}
+		if useValType {
+			scan = val
+		}
+	}
+
+	switch scan {
+	case _INT:
+		return reflect.TypeOf(int64(0))
+	case _REAL:
+		return reflect.TypeOf(float64(0))
+	case _TEXT:
+		return reflect.TypeOf("")
+	case _BLOB:
+		return reflect.TypeOf([]byte{})
+	case _BOOL:
+		return reflect.TypeOf(false)
+	case _TIME:
+		return reflect.TypeOf(time.Time{})
+	default:
+		return reflect.TypeOf((*any)(nil)).Elem()
+	}
+}
+
 func (r *rows) Next(dest []driver.Value) error {
 	old := r.Stmt.Conn().SetInterrupt(r.ctx)
 	defer r.Stmt.Conn().SetInterrupt(old)
@@ -667,7 +746,7 @@ func (r *rows) Next(dest []driver.Value) error {
 	}
 
 	data := unsafe.Slice((*any)(unsafe.SliceData(dest)), len(dest))
-	err := r.Stmt.Columns(data)
+	err := r.Stmt.Columns(data...)
 	for i := range dest {
 		if t, ok := r.decodeTime(i, dest[i]); ok {
 			dest[i] = t

driver/driver_test.go

@@ -7,6 +7,7 @@ import (
 	"errors"
 	"math"
 	"net/url"
+	"reflect"
 	"testing"
 	"time"
 
@@ -224,8 +225,8 @@ func Test_Prepare(t *testing.T) {
 	}
 
 	_, err = db.Prepare(`SELECT 1; `)
-	if err.Error() != string(util.TailErr) {
-		t.Error("want tailErr")
+	if err != nil {
+		t.Error(err)
 	}
 
 	_, err = db.Prepare(`SELECT 1; SELECT`)
@@ -365,3 +366,104 @@ func Test_time(t *testing.T) {
 		})
 	}
 }
+
+func Test_ColumnType_ScanType(t *testing.T) {
+	var (
+		INT  = reflect.TypeOf(int64(0))
+		REAL = reflect.TypeOf(float64(0))
+		TEXT = reflect.TypeOf("")
+		BLOB = reflect.TypeOf([]byte{})
+		BOOL = reflect.TypeOf(false)
+		TIME = reflect.TypeOf(time.Time{})
+		ANY  = reflect.TypeOf((*any)(nil)).Elem()
+	)
+
+	t.Parallel()
+	tmp := memdb.TestDB(t)
+
+	db, err := sql.Open("sqlite3", tmp)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer db.Close()
+
+	_, err = db.Exec(`
+		CREATE TABLE test (
+			col_int  INTEGER,
+			col_real REAL,
+			col_text TEXT,
+			col_blob BLOB,
+			col_bool BOOLEAN,
+			col_time DATETIME,
+			col_decimal DECIMAL
+		);
+		INSERT INTO test VALUES
+			(1, 1, 1, 1, 1, 1, 1),
+			(2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0),
+			('1', '1', '1', '1', '1', '1', '1'),
+			('x', 'x', 'x', 'x', 'x', 'x', 'x'),
+			(x'', x'', x'', x'', x'', x'', x''),
+			('2006-01-02T15:04:05Z', '2006-01-02T15:04:05Z', '2006-01-02T15:04:05Z', '2006-01-02T15:04:05Z',
+			 '2006-01-02T15:04:05Z', '2006-01-02T15:04:05Z', '2006-01-02T15:04:05Z'),
+			(TRUE, TRUE, TRUE, TRUE, TRUE, TRUE, TRUE),
+			(NULL, NULL, NULL, NULL, NULL, NULL, NULL);
+	`)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	rows, err := db.Query(`SELECT * FROM test`)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer rows.Close()
+
+	cols, err := rows.ColumnTypes()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	want := [][]reflect.Type{
+		{INT, REAL, TEXT, BLOB, BOOL, TIME, ANY},
+		{INT, REAL, TEXT, INT, BOOL, TIME, INT},
+		{INT, REAL, TEXT, REAL, INT, TIME, INT},
+		{INT, REAL, TEXT, TEXT, BOOL, TIME, INT},
+		{TEXT, TEXT, TEXT, TEXT, TEXT, TEXT, TEXT},
+		{BLOB, BLOB, BLOB, BLOB, BLOB, BLOB, BLOB},
+		{TEXT, TEXT, TEXT, TEXT, TEXT, TIME, TEXT},
+		{INT, REAL, TEXT, INT, BOOL, TIME, INT},
+		{ANY, ANY, ANY, BLOB, ANY, ANY, ANY},
+	}
+	for j, c := range cols {
+		got := c.ScanType()
+		if got != want[0][j] {
+			t.Errorf("want %v, got %v, at column %d", want[0][j], got, j)
+		}
+	}
+
+	dest := make([]any, len(cols))
+	for i := 1; rows.Next(); i++ {
+		cols, err := rows.ColumnTypes()
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		for j, c := range cols {
+			got := c.ScanType()
+			if got != want[i][j] {
+				t.Errorf("want %v, got %v, at row %d column %d", want[i][j], got, i, j)
+			}
+			dest[j] = reflect.New(got).Interface()
+		}
+
+		err = rows.Scan(dest...)
+		if err != nil {
+			t.Error(err)
+		}
+	}
+
+	err = rows.Err()
+	if err != nil {
+		t.Fatal(err)
+	}
+}

driver/example2_test.go

@@ -1,4 +1,4 @@
-//go:build (linux || darwin || windows || freebsd || openbsd || netbsd || dragonfly || illumos || sqlite3_flock) && !sqlite3_nosys
+//go:build linux || darwin || windows || freebsd || openbsd || netbsd || dragonfly || illumos || sqlite3_flock || sqlite3_dotlk
 
 package driver_test
 

driver/example_test.go

@@ -1,4 +1,4 @@
-//go:build ((linux || darwin || windows || freebsd || openbsd || netbsd || dragonfly || illumos) && !sqlite3_nosys) || sqlite3_flock || sqlite3_dotlk
+//go:build linux || darwin || windows || freebsd || openbsd || netbsd || dragonfly || illumos || sqlite3_flock || sqlite3_dotlk
 
 package driver_test
 

driver/savepoint_test.go

@@ -6,6 +6,7 @@ import (
 
 	"github.com/ncruces/go-sqlite3/driver"
 	_ "github.com/ncruces/go-sqlite3/embed"
+	_ "github.com/ncruces/go-sqlite3/internal/testcfg"
 	_ "github.com/ncruces/go-sqlite3/vfs/memdb"
 )
 

driver/time.go

@@ -1,8 +1,6 @@
 package driver
 
-import (
-	"time"
-)
+import "time"
 
 // Convert a string in [time.RFC3339Nano] format into a [time.Time]
 // if it roundtrips back to the same string.

driver/time_test.go

@@ -27,12 +27,12 @@ func Fuzz_stringOrTime_1(f *testing.F) {
 			// Make sure times round-trip to the same string:
 			// https://pkg.go.dev/database/sql#Rows.Scan
 			if v.Format(time.RFC3339Nano) != str {
-				t.Fatalf("did not round-trip: %q", str)
+				t.Errorf("did not round-trip: %q", str)
 			}
 		} else {
 			date, err := time.Parse(time.RFC3339Nano, str)
 			if err == nil && date.Format(time.RFC3339Nano) == str {
-				t.Fatalf("would round-trip: %q", str)
+				t.Errorf("would round-trip: %q", str)
 			}
 		}
 	})

driver/util.go

@@ -12,3 +12,63 @@ func namedValues(args []driver.Value) []driver.NamedValue {
 	}
 	return named
 }
+
+func notWhitespace(sql string) bool {
+	const (
+		code = iota
+		slash
+		minus
+		ccomment
+		sqlcomment
+		endcomment
+	)
+
+	state := code
+	for _, b := range ([]byte)(sql) {
+		if b == 0 {
+			break
+		}
+
+		switch state {
+		case code:
+			switch b {
+			case '/':
+				state = slash
+			case '-':
+				state = minus
+			case ' ', ';', '\t', '\n', '\v', '\f', '\r':
+				continue
+			default:
+				return true
+			}
+		case slash:
+			if b != '*' {
+				return true
+			}
+			state = ccomment
+		case minus:
+			if b != '-' {
+				return true
+			}
+			state = sqlcomment
+		case ccomment:
+			if b == '*' {
+				state = endcomment
+			}
+		case sqlcomment:
+			if b == '\n' {
+				state = code
+			}
+		case endcomment:
+			switch b {
+			case '/':
+				state = code
+			case '*':
+				state = endcomment
+			default:
+				state = ccomment
+			}
+		}
+	}
+	return state == slash || state == minus
+}

driver/util_test.go

@@ -1,9 +1,13 @@
 package driver
 
 import (
+	"context"
 	"database/sql/driver"
 	"reflect"
 	"testing"
+
+	_ "github.com/ncruces/go-sqlite3/embed"
+	_ "github.com/ncruces/go-sqlite3/internal/testcfg"
 )
 
 func Test_namedValues(t *testing.T) {
@@ -16,3 +20,67 @@ func Test_namedValues(t *testing.T) {
 		t.Errorf("got %v, want %v", got, want)
 	}
 }
+
+func Fuzz_notWhitespace(f *testing.F) {
+	f.Add("")
+	f.Add(" ")
+	f.Add(";")
+	f.Add("0")
+	f.Add("-")
+	f.Add("-0")
+	f.Add("--")
+	f.Add("--0")
+	f.Add("--\n")
+	f.Add("--0\n")
+	f.Add("/0")
+	f.Add("/*")
+	f.Add("/*/")
+	f.Add("/**")
+	f.Add("/*0")
+	f.Add("/**/")
+	f.Add("/***/")
+	f.Add("/**0/")
+	f.Add("\v")
+	f.Add(" \v")
+	f.Add("\xf0")
+	f.Add("\000")
+
+	db, err := Open(":memory:")
+	if err != nil {
+		f.Fatal(err)
+	}
+	defer db.Close()
+
+	f.Fuzz(func(t *testing.T, str string) {
+		if len(str) > 128 {
+			t.SkipNow()
+		}
+
+		c, err := db.Conn(context.Background())
+		if err != nil {
+			t.Fatal(err)
+		}
+		defer c.Close()
+
+		c.Raw(func(driverConn any) error {
+			conn := driverConn.(*conn).Conn
+			stmt, tail, err := conn.Prepare(str)
+			stmt.Close()
+
+			// It's hard to be bug for bug compatible with SQLite.
+			// We settle for somewhat less:
+			//   - if SQLite reports whitespace, we must too
+			//   - if we report whitespace, SQLite must not parse a statement
+			if notWhitespace(str) {
+				if stmt == nil && tail == "" && err == nil {
+					t.Errorf("was whitespace: %q", str)
+				}
+			} else {
+				if stmt != nil {
+					t.Errorf("was not whitespace: %q (%v)", str, err)
+				}
+			}
+			return nil
+		})
+	})
+}

embed/README.md

@@ -1,6 +1,6 @@
 # Embeddable Wasm build of SQLite
 
-This folder includes an embeddable Wasm build of SQLite 3.47.0 for use with
+This folder includes an embeddable Wasm build of SQLite 3.47.2 for use with
 [`github.com/ncruces/go-sqlite3`](https://pkg.go.dev/github.com/ncruces/go-sqlite3).
 
 The following optional features are compiled in:

embed/bcw2/README.md

@@ -1,6 +1,6 @@
 # Embeddable Wasm build of SQLite
 
-This folder includes an embeddable Wasm build of SQLite 3.47.0, including the experimental
+This folder includes an embeddable Wasm build of SQLite, including the experimental
 [`BEGIN CONCURRENT`](https://sqlite.org/src/doc/begin-concurrent/doc/begin_concurrent.md) and
 [Wal2](https://sqlite.org/cgi/src/doc/wal2/doc/wal2.md) patches.
 

embed/bcw2/bcw2_test.go

@@ -32,6 +32,11 @@ func Test_bcw2(t *testing.T) {
 		t.Fatal(err)
 	}
 
+	_, err = tx.Exec(`DELETE FROM test LIMIT 1`)
+	if err != nil {
+		t.Fatal(err)
+	}
+
 	err = tx.Commit()
 	if err != nil {
 		t.Fatal(err)
@@ -42,7 +47,7 @@ func Test_bcw2(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	if version != "3.47.0" {
+	if version != "3.48.0" {
 		t.Error(version)
 	}
 }

embed/bcw2/build.sh

@@ -13,15 +13,14 @@ mkdir -p build/ext/
 cp "$ROOT"/sqlite3/*.[ch] build/
 cp "$ROOT"/sqlite3/*.patch build/
 
-# https://sqlite.org/src/info/d2d954d43abe20a3
-curl -# https://sqlite.org/src/tarball/sqlite.tar.gz?r=d2d954d4 | tar xz
+# https://sqlite.org/src/info/ec5d7025cba9f4ac
+curl -# https://sqlite.org/src/tarball/sqlite.tar.gz?r=ec5d7025 | tar xz
 
 cd sqlite
 if [[ "$OSTYPE" == "msys" || "$OSTYPE" == "cygwin" ]]; then
-	MSYS_NO_PATHCONV=1 nmake /f makefile.msc sqlite3.c
+	MSYS_NO_PATHCONV=1 nmake /f makefile.msc sqlite3.c OPTS=-DSQLITE_ENABLE_UPDATE_DELETE_LIMIT
 else
-	sh configure
-	make sqlite3.c
+	sh configure --enable-update-limit && make sqlite3.c
 fi
 cd ~-
 
@@ -54,6 +53,7 @@ cd ~-
 	-Wl,--import-undefined \
 	-Wl,--initial-memory=327680 \
 	-D_HAVE_SQLITE_CONFIG_H \
+	-DSQLITE_ENABLE_UPDATE_DELETE_LIMIT \
 	-DSQLITE_CUSTOM_INCLUDE=sqlite_opt.h \
 	$(awk '{print "-Wl,--export="$0}' ../exports.txt)
 

embed/bcw2/go.mod

@@ -0,0 +1,13 @@
+module github.com/ncruces/go-sqlite3/embed/bcw2
+
+go 1.21
+
+toolchain go1.23.0
+
+require github.com/ncruces/go-sqlite3 v0.21.0
+
+require (
+	github.com/ncruces/julianday v1.0.0 // indirect
+	github.com/tetratelabs/wazero v1.8.2 // indirect
+	golang.org/x/sys v0.28.0 // indirect
+)

embed/bcw2/go.sum

@@ -0,0 +1,10 @@
+github.com/ncruces/go-sqlite3 v0.21.0 h1:EwKFoy1hHEopN4sFZarmi+McXdbCcbTuLixhEayXVbQ=
+github.com/ncruces/go-sqlite3 v0.21.0/go.mod h1:zxMOaSG5kFYVFK4xQa0pdwIszqxqJ0W0BxBgwdrNjuA=
+github.com/ncruces/julianday v1.0.0 h1:fH0OKwa7NWvniGQtxdJRxAgkBMolni2BjDHaWTxqt7M=
+github.com/ncruces/julianday v1.0.0/go.mod h1:Dusn2KvZrrovOMJuOt0TNXL6tB7U2E8kvza5fFc9G7g=
+github.com/tetratelabs/wazero v1.8.2 h1:yIgLR/b2bN31bjxwXHD8a3d+BogigR952csSDdLYEv4=
+github.com/tetratelabs/wazero v1.8.2/go.mod h1:yAI0XTsMBhREkM/YDAK/zNou3GoiAce1P6+rp/wQhjs=
+golang.org/x/sys v0.28.0 h1:Fksou7UEQUWlKvIdsqzJmUmCX3cZuD2+P3XyyzwMhlA=
+golang.org/x/sys v0.28.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
+golang.org/x/text v0.21.0 h1:zyQAAkrwaneQ066sspRyJaG9VNi/YJ1NfzcGB3hZ/qo=
+golang.org/x/text v0.21.0/go.mod h1:4IBbMaMmOPCJ8SecivzSH54+73PCFmPWxNTLm+vZkEQ=

embed/init_test.go

@@ -19,7 +19,7 @@ func Test_init(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	if version != "3.47.0" {
+	if version != "3.47.2" {
 		t.Error(version)
 	}
 }

ext/blobio/blob.go

@@ -44,6 +44,8 @@ func Register(db *sqlite3.Conn) error {
 type OpenCallback func(*sqlite3.Blob, ...sqlite3.Value) error
 
 func readblob(ctx sqlite3.Context, arg ...sqlite3.Value) {
+	_ = arg[5] // bounds check
+
 	blob, err := getAuxBlob(ctx, arg, false)
 	if err != nil {
 		ctx.ResultError(err)
@@ -78,6 +80,8 @@ func readblob(ctx sqlite3.Context, arg ...sqlite3.Value) {
 }
 
 func writeblob(ctx sqlite3.Context, arg ...sqlite3.Value) {
+	_ = arg[5] // bounds check
+
 	blob, err := getAuxBlob(ctx, arg, true)
 	if err != nil {
 		ctx.ResultError(err)

ext/regexp/regexp.go

@@ -76,6 +76,7 @@ func load(ctx sqlite3.Context, i int, expr string) (*regexp.Regexp, error) {
 }
 
 func regex(ctx sqlite3.Context, arg ...sqlite3.Value) {
+	_ = arg[1] // bounds check
 	re, err := load(ctx, 0, arg[0].Text())
 	if err != nil {
 		ctx.ResultError(err)
@@ -165,6 +166,8 @@ func regexInstr(ctx sqlite3.Context, arg ...sqlite3.Value) {
 }
 
 func regexReplace(ctx sqlite3.Context, arg ...sqlite3.Value) {
+	_ = arg[2] // bounds check
+
 	re, err := load(ctx, 1, arg[1].Text())
 	if err != nil {
 		ctx.ResultError(err)

ext/unicode/unicode.go

@@ -189,6 +189,7 @@ func like(ctx sqlite3.Context, arg ...sqlite3.Value) {
 			return
 		}
 	}
+	_ = arg[1] // bounds check
 
 	type likeData struct {
 		*regexp.Regexp

go.mod

@@ -5,17 +5,20 @@ go 1.21
 toolchain go1.23.0
 
 require (
-	github.com/dchest/siphash v1.2.3
-	github.com/google/uuid v1.6.0
 	github.com/ncruces/julianday v1.0.0
 	github.com/ncruces/sort v0.1.2
-	github.com/psanford/httpreadat v0.1.0
-	github.com/tetratelabs/wazero v1.8.1
-	golang.org/x/crypto v0.28.0
-	golang.org/x/sync v0.8.0
-	golang.org/x/sys v0.26.0
-	golang.org/x/text v0.19.0
-	lukechampine.com/adiantum v1.1.1
+	github.com/tetratelabs/wazero v1.8.2
+	golang.org/x/crypto v0.31.0
+	golang.org/x/sys v0.28.0
+)
+
+require (
+	github.com/dchest/siphash v1.2.3 // ext/bloom
+	github.com/google/uuid v1.6.0 // ext/uuid
+	github.com/psanford/httpreadat v0.1.0 // example
+	golang.org/x/sync v0.10.0 // test
+	golang.org/x/text v0.21.0 // ext/unicode
+	lukechampine.com/adiantum v1.1.1 // vfs/adiantum
 )
 
 retract v0.4.0 // tagged from the wrong branch

go.sum

@@ -8,15 +8,15 @@ github.com/ncruces/sort v0.1.2 h1:zKQ9CA4fpHPF6xsUhRTfi5EEryspuBpe/QA4VWQOV1U=
 github.com/ncruces/sort v0.1.2/go.mod h1:vEJUTBJtebIuCMmXD18GKo5GJGhsay+xZFOoBEIXFmE=
 github.com/psanford/httpreadat v0.1.0 h1:VleW1HS2zO7/4c7c7zNl33fO6oYACSagjJIyMIwZLUE=
 github.com/psanford/httpreadat v0.1.0/go.mod h1:Zg7P+TlBm3bYbyHTKv/EdtSJZn3qwbPwpfZ/I9GKCRE=
-github.com/tetratelabs/wazero v1.8.1 h1:NrcgVbWfkWvVc4UtT4LRLDf91PsOzDzefMdwhLfA550=
-github.com/tetratelabs/wazero v1.8.1/go.mod h1:yAI0XTsMBhREkM/YDAK/zNou3GoiAce1P6+rp/wQhjs=
-golang.org/x/crypto v0.28.0 h1:GBDwsMXVQi34v5CCYUm2jkJvu4cbtru2U4TN2PSyQnw=
-golang.org/x/crypto v0.28.0/go.mod h1:rmgy+3RHxRZMyY0jjAJShp2zgEdOqj2AO7U0pYmeQ7U=
-golang.org/x/sync v0.8.0 h1:3NFvSEYkUoMifnESzZl15y791HH1qU2xm6eCJU5ZPXQ=
-golang.org/x/sync v0.8.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=
-golang.org/x/sys v0.26.0 h1:KHjCJyddX0LoSTb3J+vWpupP9p0oznkqVk/IfjymZbo=
-golang.org/x/sys v0.26.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
-golang.org/x/text v0.19.0 h1:kTxAhCbGbxhK0IwgSKiMO5awPoDQ0RpfiVYBfK860YM=
-golang.org/x/text v0.19.0/go.mod h1:BuEKDfySbSR4drPmRPG/7iBdf8hvFMuRexcpahXilzY=
+github.com/tetratelabs/wazero v1.8.2 h1:yIgLR/b2bN31bjxwXHD8a3d+BogigR952csSDdLYEv4=
+github.com/tetratelabs/wazero v1.8.2/go.mod h1:yAI0XTsMBhREkM/YDAK/zNou3GoiAce1P6+rp/wQhjs=
+golang.org/x/crypto v0.31.0 h1:ihbySMvVjLAeSH1IbfcRTkD/iNscyz8rGzjF/E5hV6U=
+golang.org/x/crypto v0.31.0/go.mod h1:kDsLvtWBEx7MV9tJOj9bnXsPbxwJQ6csT/x4KIN4Ssk=
+golang.org/x/sync v0.10.0 h1:3NQrjDixjgGwUOCaF8w2+VYHv0Ve/vGYSbdkTa98gmQ=
+golang.org/x/sync v0.10.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=
+golang.org/x/sys v0.28.0 h1:Fksou7UEQUWlKvIdsqzJmUmCX3cZuD2+P3XyyzwMhlA=
+golang.org/x/sys v0.28.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
+golang.org/x/text v0.21.0 h1:zyQAAkrwaneQ066sspRyJaG9VNi/YJ1NfzcGB3hZ/qo=
+golang.org/x/text v0.21.0/go.mod h1:4IBbMaMmOPCJ8SecivzSH54+73PCFmPWxNTLm+vZkEQ=
 lukechampine.com/adiantum v1.1.1 h1:4fp6gTxWCqpEbLy40ExiYDDED3oUNWx5cTqBCtPdZqA=
 lukechampine.com/adiantum v1.1.1/go.mod h1:LrAYVnTYLnUtE/yMp5bQr0HstAf060YUF8nM0B6+rUw=

go.work

@@ -3,4 +3,5 @@ go 1.21
 use (
 	.
 	./gormlite
+	./embed/bcw2
 )

go.work.sum

@@ -1,3 +1,4 @@
+github.com/ncruces/go-sqlite3 v0.21.0/go.mod h1:zxMOaSG5kFYVFK4xQa0pdwIszqxqJ0W0BxBgwdrNjuA=
 golang.org/x/mod v0.8.0/go.mod h1:iBbtSCu2XBx23ZKBPSOrRkjjQPZFPuis4dIYUhu/chs=
 golang.org/x/mod v0.17.0/go.mod h1:hTbmBsO62+eylJbnUtE2MGJUyE7QWk4xUqPFrRgJ+7c=
 golang.org/x/net v0.21.0/go.mod h1:bIjVDfnllIU7BJ2DNgfnXvpSvtn8VRwhlsaeUTyUS44=
@@ -9,5 +10,7 @@ golang.org/x/term v0.22.0/go.mod h1:F3qCibpT5AMpCRfhfT53vVJwhLtIVHhB9XDjfFvnMI4=
 golang.org/x/term v0.23.0/go.mod h1:DgV24QBUrK6jhZXl+20l6UWznPlwAHm1Q1mGHtydmSk=
 golang.org/x/term v0.24.0/go.mod h1:lOBK/LVxemqiMij05LGJ0tzNr8xlmwBRJ81PX6wVLH8=
 golang.org/x/term v0.25.0/go.mod h1:RPyXicDX+6vLxogjjRxjgD2TKtmAO6NZBsBRfrOLu7M=
+golang.org/x/term v0.26.0/go.mod h1:Si5m1o57C5nBNQo5z1iq+XDijt21BDBDp2bK0QI8e3E=
+golang.org/x/term v0.27.0/go.mod h1:iMsnZpn0cago0GOrHO2+Y7u7JPn5AylBrcoWkElMTSM=
 golang.org/x/tools v0.6.0/go.mod h1:Xwgl3UAJ/d3gWutnCtw505GrjyAbvKui8lOU390QaIU=
 golang.org/x/tools v0.21.1-0.20240508182429-e35e4ccd0d2d/go.mod h1:aiJjzUbINMkxbQROHiO6hDPo2LHcIPhhQsa9DLh0yGk=

gormlite/go.mod

@@ -5,7 +5,7 @@ go 1.21
 toolchain go1.23.0
 
 require (
-	github.com/ncruces/go-sqlite3 v0.20.0
+	github.com/ncruces/go-sqlite3 v0.21.0
 	gorm.io/gorm v1.25.12
 )
 
@@ -13,7 +13,7 @@ require (
 	github.com/jinzhu/inflection v1.0.0 // indirect
 	github.com/jinzhu/now v1.1.5 // indirect
 	github.com/ncruces/julianday v1.0.0 // indirect
-	github.com/tetratelabs/wazero v1.8.1 // indirect
-	golang.org/x/sys v0.26.0 // indirect
-	golang.org/x/text v0.19.0 // indirect
+	github.com/tetratelabs/wazero v1.8.2 // indirect
+	golang.org/x/sys v0.28.0 // indirect
+	golang.org/x/text v0.21.0 // indirect
 )

gormlite/go.sum

@@ -2,15 +2,15 @@ github.com/jinzhu/inflection v1.0.0 h1:K317FqzuhWc8YvSVlFMCCUb36O/S9MCKRDI7QkRKD
 github.com/jinzhu/inflection v1.0.0/go.mod h1:h+uFLlag+Qp1Va5pdKtLDYj+kHp5pxUVkryuEj+Srlc=
 github.com/jinzhu/now v1.1.5 h1:/o9tlHleP7gOFmsnYNz3RGnqzefHA47wQpKrrdTIwXQ=
 github.com/jinzhu/now v1.1.5/go.mod h1:d3SSVoowX0Lcu0IBviAWJpolVfI5UJVZZ7cO71lE/z8=
-github.com/ncruces/go-sqlite3 v0.20.0 h1:/nBLvYxj7sk9S6y57nmMFvoQ/KJtGo0pNi8J80s8oJU=
-github.com/ncruces/go-sqlite3 v0.20.0/go.mod h1:yL4ZNWGsr1/8pcLfpPW1RT1WFdvyeHonrgIwwi4rvkg=
+github.com/ncruces/go-sqlite3 v0.21.0 h1:EwKFoy1hHEopN4sFZarmi+McXdbCcbTuLixhEayXVbQ=
+github.com/ncruces/go-sqlite3 v0.21.0/go.mod h1:zxMOaSG5kFYVFK4xQa0pdwIszqxqJ0W0BxBgwdrNjuA=
 github.com/ncruces/julianday v1.0.0 h1:fH0OKwa7NWvniGQtxdJRxAgkBMolni2BjDHaWTxqt7M=
 github.com/ncruces/julianday v1.0.0/go.mod h1:Dusn2KvZrrovOMJuOt0TNXL6tB7U2E8kvza5fFc9G7g=
-github.com/tetratelabs/wazero v1.8.1 h1:NrcgVbWfkWvVc4UtT4LRLDf91PsOzDzefMdwhLfA550=
-github.com/tetratelabs/wazero v1.8.1/go.mod h1:yAI0XTsMBhREkM/YDAK/zNou3GoiAce1P6+rp/wQhjs=
-golang.org/x/sys v0.26.0 h1:KHjCJyddX0LoSTb3J+vWpupP9p0oznkqVk/IfjymZbo=
-golang.org/x/sys v0.26.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
-golang.org/x/text v0.19.0 h1:kTxAhCbGbxhK0IwgSKiMO5awPoDQ0RpfiVYBfK860YM=
-golang.org/x/text v0.19.0/go.mod h1:BuEKDfySbSR4drPmRPG/7iBdf8hvFMuRexcpahXilzY=
+github.com/tetratelabs/wazero v1.8.2 h1:yIgLR/b2bN31bjxwXHD8a3d+BogigR952csSDdLYEv4=
+github.com/tetratelabs/wazero v1.8.2/go.mod h1:yAI0XTsMBhREkM/YDAK/zNou3GoiAce1P6+rp/wQhjs=
+golang.org/x/sys v0.28.0 h1:Fksou7UEQUWlKvIdsqzJmUmCX3cZuD2+P3XyyzwMhlA=
+golang.org/x/sys v0.28.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
+golang.org/x/text v0.21.0 h1:zyQAAkrwaneQ066sspRyJaG9VNi/YJ1NfzcGB3hZ/qo=
+golang.org/x/text v0.21.0/go.mod h1:4IBbMaMmOPCJ8SecivzSH54+73PCFmPWxNTLm+vZkEQ=
 gorm.io/gorm v1.25.12 h1:I0u8i2hWQItBq1WfE0o2+WuL9+8L21K9e2HHSTE/0f8=
 gorm.io/gorm v1.25.12/go.mod h1:xh7N7RHfYlNc5EmcI/El95gXusucDrQnHXe0+CgWcLQ=

internal/alloc/alloc_other.go

@@ -1,4 +1,4 @@
-//go:build !(unix || windows) || sqlite3_nosys
+//go:build !unix && !windows
 
 package alloc
 

internal/alloc/alloc_unix.go

@@ -1,4 +1,4 @@
-//go:build unix && !sqlite3_nosys
+//go:build unix
 
 package alloc
 

internal/alloc/alloc_windows.go

@@ -1,5 +1,3 @@
-//go:build !sqlite3_nosys
-
 package alloc
 
 import (

internal/dotlk/dotlk.go

@@ -0,0 +1,29 @@
+package dotlk
+
+import (
+	"errors"
+	"io/fs"
+	"os"
+)
+
+// LockShm creates a directory on disk to prevent SQLite
+// from using this path for a shared memory file.
+func LockShm(name string) error {
+	err := os.Mkdir(name, 0777)
+	if errors.Is(err, fs.ErrExist) {
+		s, err := os.Lstat(name)
+		if err == nil && s.IsDir() {
+			return nil
+		}
+	}
+	return err
+}
+
+// Unlock removes the lock or shared memory file.
+func Unlock(name string) error {
+	err := os.Remove(name)
+	if errors.Is(err, fs.ErrNotExist) {
+		return nil
+	}
+	return err
+}

internal/dotlk/dotlk_other.go

@@ -0,0 +1,13 @@
+//go:build !unix
+
+package dotlk
+
+import "os"
+
+// TryLock returns nil if it acquired the lock,
+// fs.ErrExist if another process has the lock.
+func TryLock(name string) error {
+	f, err := os.OpenFile(name, os.O_RDWR|os.O_CREATE|os.O_EXCL, 0666)
+	f.Close()
+	return err
+}

internal/dotlk/dotlk_unix.go

@@ -0,0 +1,50 @@
+//go:build unix
+
+package dotlk
+
+import (
+	"errors"
+	"io/fs"
+	"os"
+	"strconv"
+
+	"golang.org/x/sys/unix"
+)
+
+// TryLock returns nil if it acquired the lock,
+// fs.ErrExist if another process has the lock.
+func TryLock(name string) error {
+	for retry := true; retry; retry = false {
+		f, err := os.OpenFile(name, os.O_RDWR|os.O_CREATE|os.O_EXCL, 0666)
+		if err == nil {
+			f.WriteString(strconv.Itoa(os.Getpid()))
+			f.Close()
+			return nil
+		}
+		if !errors.Is(err, fs.ErrExist) {
+			return err
+		}
+		if !removeStale(name) {
+			break
+		}
+	}
+	return fs.ErrExist
+}
+
+func removeStale(name string) bool {
+	buf, err := os.ReadFile(name)
+	if err != nil {
+		return errors.Is(err, fs.ErrNotExist)
+	}
+
+	pid, err := strconv.Atoi(string(buf))
+	if err != nil {
+		return false
+	}
+	if unix.Kill(pid, 0) == nil {
+		return false
+	}
+
+	err = os.Remove(name)
+	return err == nil || errors.Is(err, fs.ErrNotExist)
+}

internal/util/mmap_other.go

@@ -1,4 +1,4 @@
-//go:build !unix || sqlite3_nosys
+//go:build !unix
 
 package util
 

internal/util/mmap_unix.go

@@ -1,4 +1,4 @@
-//go:build unix && !sqlite3_nosys
+//go:build unix
 
 package util
 
@@ -39,13 +39,13 @@ func (s *mmapState) new(ctx context.Context, mod api.Module, size int32) *Mapped
 	// Save the newly allocated region.
 	ptr := uint32(stack[0])
 	buf := View(mod, ptr, uint64(size))
-	addr := unsafe.Pointer(&buf[0])
-	s.regions = append(s.regions, &MappedRegion{
+	res := &MappedRegion{
 		Ptr:  ptr,
-		addr: addr,
 		size: size,
-	})
-	return s.regions[len(s.regions)-1]
+		addr: unsafe.Pointer(&buf[0]),
+	}
+	s.regions = append(s.regions, res)
+	return res
 }
 
 type MappedRegion struct {

internal/util/mmap_windows.go

@@ -1,5 +1,3 @@
-//go:build !sqlite3_nosys
-
 package util
 
 import (

sqlite.go

@@ -265,10 +265,11 @@ func (a *arena) mark() (reset func()) {
 	ptrs := len(a.ptrs)
 	next := a.next
 	return func() {
-		for _, ptr := range a.ptrs[ptrs:] {
+		rest := a.ptrs[ptrs:]
+		for _, ptr := range a.ptrs[:ptrs] {
 			a.sqlt.free(ptr)
 		}
-		a.ptrs = a.ptrs[:ptrs]
+		a.ptrs = rest
 		a.next = next
 	}
 }

sqlite3/busy_timeout.patch

@@ -2,7 +2,7 @@
 # handle, and interrupt, sqlite3_busy_timeout.
 --- sqlite3.c.orig
 +++ sqlite3.c
-@@ -182908,7 +182908,7 @@
+@@ -182928,7 +182928,7 @@
    if( !sqlite3SafetyCheckOk(db) ) return SQLITE_MISUSE_BKPT;
  #endif
    if( ms>0 ){

sqlite3/column.c

@@ -38,6 +38,9 @@ int sqlite3_columns_go(sqlite3_stmt *stmt, int nCol, char *aType,
     }
     if (ptr == NULL && rc == SQLITE_OK) {
       rc = sqlite3_errcode(sqlite3_db_handle(stmt));
+      if (rc == SQLITE_ROW || rc == SQLITE_DONE) {
+        rc = SQLITE_OK;
+      }
     }
     aData[i].ptr = ptr;
     aData[i].len = sqlite3_column_bytes(stmt, i);

sqlite3/download.sh

@@ -3,7 +3,7 @@ set -euo pipefail
 
 cd -P -- "$(dirname -- "$0")"
 
-curl -#OL "https://sqlite.org/2024/sqlite-amalgamation-3470000.zip"
+curl -#OL "https://sqlite.org/2024/sqlite-amalgamation-3470200.zip"
 unzip -d . sqlite-amalgamation-*.zip
 mv sqlite-amalgamation-*/sqlite3.c .
 mv sqlite-amalgamation-*/sqlite3.h .
@@ -21,25 +21,25 @@ cat *.patch | patch --no-backup-if-mismatch
 
 mkdir -p ext/
 cd ext/
-curl -#OL "https://github.com/sqlite/sqlite/raw/version-3.47.0/ext/misc/anycollseq.c"
-curl -#OL "https://github.com/sqlite/sqlite/raw/version-3.47.0/ext/misc/base64.c"
-curl -#OL "https://github.com/sqlite/sqlite/raw/version-3.47.0/ext/misc/decimal.c"
-curl -#OL "https://github.com/sqlite/sqlite/raw/version-3.47.0/ext/misc/ieee754.c"
-curl -#OL "https://github.com/sqlite/sqlite/raw/version-3.47.0/ext/misc/regexp.c"
-curl -#OL "https://github.com/sqlite/sqlite/raw/version-3.47.0/ext/misc/series.c"
-curl -#OL "https://github.com/sqlite/sqlite/raw/version-3.47.0/ext/misc/spellfix.c"
-curl -#OL "https://github.com/sqlite/sqlite/raw/version-3.47.0/ext/misc/uint.c"
+curl -#OL "https://github.com/sqlite/sqlite/raw/version-3.47.2/ext/misc/anycollseq.c"
+curl -#OL "https://github.com/sqlite/sqlite/raw/version-3.47.2/ext/misc/base64.c"
+curl -#OL "https://github.com/sqlite/sqlite/raw/version-3.47.2/ext/misc/decimal.c"
+curl -#OL "https://github.com/sqlite/sqlite/raw/version-3.47.2/ext/misc/ieee754.c"
+curl -#OL "https://github.com/sqlite/sqlite/raw/version-3.47.2/ext/misc/regexp.c"
+curl -#OL "https://github.com/sqlite/sqlite/raw/version-3.47.2/ext/misc/series.c"
+curl -#OL "https://github.com/sqlite/sqlite/raw/version-3.47.2/ext/misc/spellfix.c"
+curl -#OL "https://github.com/sqlite/sqlite/raw/version-3.47.2/ext/misc/uint.c"
 cd ~-
 
 cd ../vfs/tests/mptest/testdata/
-curl -#OL "https://github.com/sqlite/sqlite/raw/version-3.47.0/mptest/mptest.c"
-curl -#OL "https://github.com/sqlite/sqlite/raw/version-3.47.0/mptest/config01.test"
-curl -#OL "https://github.com/sqlite/sqlite/raw/version-3.47.0/mptest/config02.test"
-curl -#OL "https://github.com/sqlite/sqlite/raw/version-3.47.0/mptest/crash01.test"
-curl -#OL "https://github.com/sqlite/sqlite/raw/version-3.47.0/mptest/crash02.subtest"
-curl -#OL "https://github.com/sqlite/sqlite/raw/version-3.47.0/mptest/multiwrite01.test"
+curl -#OL "https://github.com/sqlite/sqlite/raw/version-3.47.2/mptest/mptest.c"
+curl -#OL "https://github.com/sqlite/sqlite/raw/version-3.47.2/mptest/config01.test"
+curl -#OL "https://github.com/sqlite/sqlite/raw/version-3.47.2/mptest/config02.test"
+curl -#OL "https://github.com/sqlite/sqlite/raw/version-3.47.2/mptest/crash01.test"
+curl -#OL "https://github.com/sqlite/sqlite/raw/version-3.47.2/mptest/crash02.subtest"
+curl -#OL "https://github.com/sqlite/sqlite/raw/version-3.47.2/mptest/multiwrite01.test"
 cd ~-
 
 cd ../vfs/tests/speedtest1/testdata/
-curl -#OL "https://github.com/sqlite/sqlite/raw/version-3.47.0/test/speedtest1.c"
+curl -#OL "https://github.com/sqlite/sqlite/raw/version-3.47.2/test/speedtest1.c"
 cd ~-

sqlite3/vfs_find.patch

@@ -1,7 +1,7 @@
 # Remove VFS registration. Go handles it.
 --- sqlite3.c.orig
 +++ sqlite3.c
-@@ -26594,7 +26594,7 @@
+@@ -26603,7 +26603,7 @@
    sqlite3_free(p);
    return sqlite3_os_init();
  }
@@ -10,7 +10,7 @@
  /*
  ** The list of all registered VFS implementations.
  */
-@@ -26691,7 +26691,7 @@
+@@ -26700,7 +26700,7 @@
    sqlite3_mutex_leave(mutex);
    return SQLITE_OK;
  }

stmt.go

@@ -582,7 +582,9 @@ func (s *Stmt) ColumnRawBlob(col int) []byte {
 func (s *Stmt) columnRawBytes(col int, ptr uint32) []byte {
 	if ptr == 0 {
 		r := s.c.call("sqlite3_errcode", uint64(s.c.handle))
-		s.err = s.c.error(r)
+		if r != _ROW && r != _DONE {
+			s.err = s.c.error(r)
+		}
 		return nil
 	}
 
@@ -637,7 +639,7 @@ func (s *Stmt) ColumnValue(col int) Value {
 // [TEXT] as string, and [BLOB] as []byte.
 // Any []byte are owned by SQLite and may be invalidated by
 // subsequent calls to [Stmt] methods.
-func (s *Stmt) Columns(dest []any) error {
+func (s *Stmt) Columns(dest ...any) error {
 	defer s.c.arena.mark()()
 	count := uint64(len(dest))
 	typePtr := s.c.arena.new(count)
@@ -666,6 +668,10 @@ func (s *Stmt) Columns(dest []any) error {
 			dest[i] = nil
 		default:
 			ptr := util.ReadUint32(s.c.mod, dataPtr+0)
+			if ptr == 0 {
+				dest[i] = []byte{}
+				continue
+			}
 			len := util.ReadUint32(s.c.mod, dataPtr+4)
 			buf := util.View(s.c.mod, ptr, uint64(len))
 			if types[i] == byte(TEXT) {

tests/bradfitz/sql_test.go

@@ -1,4 +1,4 @@
-//go:build ((linux || darwin || windows || freebsd || openbsd || netbsd || dragonfly || illumos) && !sqlite3_nosys) || sqlite3_flock || sqlite3_dotlk
+//go:build linux || darwin || windows || freebsd || openbsd || netbsd || dragonfly || illumos || sqlite3_flock || sqlite3_dotlk
 
 package bradfitz
 

util/osutil/open_windows.go

@@ -101,6 +101,9 @@ func syscallOpen(path string, mode int, perm uint32) (fd Handle, err error) {
 		const _FILE_FLAG_WRITE_THROUGH = 0x80000000
 		attrs |= _FILE_FLAG_WRITE_THROUGH
 	}
+	if mode&O_NONBLOCK != 0 {
+		attrs |= FILE_FLAG_OVERLAPPED
+	}
 	return CreateFile(pathp, access, sharemode, sa, createmode, attrs, 0)
 }
 

vfs/README.md

@@ -30,7 +30,6 @@ like SQLite.
 
 You can also opt into a cross-platform locking implementation
 with the `sqlite3_dotlk` build tag.
-The only requirement is an atomic `os.Mkdir`.
 
 Otherwise, file locking is not supported, and you must use
 [`nolock=1`](https://sqlite.org/uri.html#urinolock)
@@ -49,11 +48,6 @@ On Unix, this package may use `mmap` to implement
 [shared-memory for the WAL-index](https://sqlite.org/wal.html#implementation_of_shared_memory_for_the_wal_index),
 like SQLite.
 
-With [BSD locks](https://man.freebsd.org/cgi/man.cgi?query=flock&sektion=2)
-a WAL database can only be accessed by a single proccess.
-Other processes that attempt to access a database locked with BSD locks,
-will fail with the [`SQLITE_PROTOCOL`](https://sqlite.org/rescode.html#protocol) error code.
-
 On Windows, this package may use `MapViewOfFile`, like SQLite.
 
 You can also opt into a cross-platform, in-process, memory sharing implementation
@@ -92,7 +86,6 @@ The implementation is compatible with SQLite's
 The VFS can be customized with a few build tags:
 - `sqlite3_flock` forces the use of BSD locks.
 - `sqlite3_dotlk` forces the use of dot-file locks.
-- `sqlite3_nosys` prevents importing [`x/sys`](https://pkg.go.dev/golang.org/x/sys).
 
 > [!IMPORTANT]
 > The default configuration of this package is compatible with the standard

vfs/adiantum/example_test.go

@@ -1,4 +1,4 @@
-//go:build ((linux || darwin || windows || freebsd || openbsd || netbsd || dragonfly || illumos) && !sqlite3_nosys) || sqlite3_flock || sqlite3_dotlk
+//go:build linux || darwin || windows || freebsd || openbsd || netbsd || dragonfly || illumos || sqlite3_flock || sqlite3_dotlk
 
 package adiantum_test
 

vfs/adiantum/hbsh.go

@@ -198,11 +198,13 @@ func (h *hbshFile) WriteAt(p []byte, off int64) (n int, err error) {
 func (h *hbshFile) DeviceCharacteristics() vfs.DeviceCharacteristic {
 	var _ [0]struct{} = [blockSize - 4096]struct{}{} // Ensure blockSize is 4K.
 	return h.File.DeviceCharacteristics() & (0 |
-		// The only safe flags are these:
+		// These flags are safe:
 		vfs.IOCAP_ATOMIC4K |
-		vfs.IOCAP_UNDELETABLE_WHEN_OPEN |
 		vfs.IOCAP_IMMUTABLE |
-		vfs.IOCAP_BATCH_ATOMIC)
+		vfs.IOCAP_SEQUENTIAL |
+		vfs.IOCAP_SUBPAGE_READ |
+		vfs.IOCAP_BATCH_ATOMIC |
+		vfs.IOCAP_UNDELETABLE_WHEN_OPEN)
 }
 
 func (h *hbshFile) SectorSize() int {

vfs/cksm.go

@@ -101,6 +101,14 @@ func (c cksmFile) Pragma(name string, value string) (string, error) {
 	return "", _NOTFOUND
 }
 
+func (c cksmFile) DeviceCharacteristics() DeviceCharacteristic {
+	res := c.File.DeviceCharacteristics()
+	if c.verifyCksm {
+		res &^= IOCAP_SUBPAGE_READ
+	}
+	return res
+}
+
 func (c cksmFile) fileControl(ctx context.Context, mod api.Module, op _FcntlOpcode, pArg uint32) _ErrorCode {
 	switch op {
 	case _FCNTL_CKPT_START:

vfs/const.go

@@ -177,6 +177,7 @@ const (
 	IOCAP_POWERSAFE_OVERWRITE   DeviceCharacteristic = 0x00001000
 	IOCAP_IMMUTABLE             DeviceCharacteristic = 0x00002000
 	IOCAP_BATCH_ATOMIC          DeviceCharacteristic = 0x00004000
+	IOCAP_SUBPAGE_READ          DeviceCharacteristic = 0x00008000
 )
 
 // https://sqlite.org/c3ref/c_fcntl_begin_atomic_write.html

vfs/file.go

@@ -187,7 +187,7 @@ func (f *vfsFile) SectorSize() int {
 }
 
 func (f *vfsFile) DeviceCharacteristics() DeviceCharacteristic {
-	var res DeviceCharacteristic
+	res := IOCAP_SUBPAGE_READ
 	if osBatchAtomic(f.File) {
 		res |= IOCAP_BATCH_ATOMIC
 	}

vfs/lock.go

@@ -1,4 +1,4 @@
-//go:build ((linux || darwin || windows || freebsd || openbsd || netbsd || dragonfly || illumos) && !sqlite3_nosys) || sqlite3_flock || sqlite3_dotlk
+//go:build linux || darwin || windows || freebsd || openbsd || netbsd || dragonfly || illumos || sqlite3_flock || sqlite3_dotlk
 
 package vfs
 
@@ -20,12 +20,10 @@ const (
 )
 
 func (f *vfsFile) Lock(lock LockLevel) error {
-	// Argument check. SQLite never explicitly requests a pending lock.
-	if lock != LOCK_SHARED && lock != LOCK_RESERVED && lock != LOCK_EXCLUSIVE {
-		panic(util.AssertErr())
-	}
-
 	switch {
+	case lock != LOCK_SHARED && lock != LOCK_RESERVED && lock != LOCK_EXCLUSIVE:
+		// Argument check. SQLite never explicitly requests a pending lock.
+		panic(util.AssertErr())
 	case f.lock < LOCK_NONE || f.lock > LOCK_EXCLUSIVE:
 		// Connection state check.
 		panic(util.AssertErr())
@@ -87,13 +85,12 @@ func (f *vfsFile) Lock(lock LockLevel) error {
 }
 
 func (f *vfsFile) Unlock(lock LockLevel) error {
-	// Argument check.
-	if lock != LOCK_NONE && lock != LOCK_SHARED {
+	switch {
+	case lock != LOCK_NONE && lock != LOCK_SHARED:
+		// Argument check.
 		panic(util.AssertErr())
-	}
-
-	// Connection state check.
-	if f.lock < LOCK_NONE || f.lock > LOCK_EXCLUSIVE {
+	case f.lock < LOCK_NONE || f.lock > LOCK_EXCLUSIVE:
+		// Connection state check.
 		panic(util.AssertErr())
 	}
 

vfs/lock_other.go

@@ -1,4 +1,4 @@
-//go:build !(((linux || darwin || windows || freebsd || openbsd || netbsd || dragonfly || illumos) && !sqlite3_nosys) || sqlite3_flock || sqlite3_dotlk)
+//go:build !(linux || darwin || windows || freebsd || openbsd || netbsd || dragonfly || illumos || sqlite3_flock || sqlite3_dotlk)
 
 package vfs
 

vfs/os_bsd.go

@@ -1,4 +1,4 @@
-//go:build ((freebsd || openbsd || netbsd || dragonfly || illumos) && !(sqlite3_dotlk || sqlite3_nosys)) || sqlite3_flock
+//go:build ((freebsd || openbsd || netbsd || dragonfly || illumos) && !sqlite3_dotlk) || sqlite3_flock
 
 package vfs
 
@@ -9,15 +9,21 @@ import (
 )
 
 func osGetSharedLock(file *os.File) _ErrorCode {
-	return osLock(file, unix.LOCK_SH|unix.LOCK_NB, _IOERR_RDLOCK)
+	return osFlock(file, unix.LOCK_SH|unix.LOCK_NB, _IOERR_RDLOCK)
 }
 
 func osGetReservedLock(file *os.File) _ErrorCode {
-	rc := osLock(file, unix.LOCK_EX|unix.LOCK_NB, _IOERR_LOCK)
+	rc := osFlock(file, unix.LOCK_EX|unix.LOCK_NB, _IOERR_LOCK)
 	if rc == _BUSY {
-		// The documentation states the lock is upgraded by releasing the previous lock,
-		// then acquiring the new lock.
-		// This is a race, so return BUSY_SNAPSHOT to ensure the transaction is aborted.
+		// The documentation states that a lock is upgraded by
+		// releasing the previous lock, then acquiring the new lock.
+		// Going over the source code of various BSDs, though,
+		// with LOCK_NB, the lock is not released,
+		// and EAGAIN is returned holding the shared lock.
+		// Still, if we're already in a transaction, we want to abort it,
+		// so return BUSY_SNAPSHOT here. If there's no transaction active,
+		// SQLite will change this back to SQLITE_BUSY,
+		// and invoke the busy handler if appropriate.
 		return _BUSY_SNAPSHOT
 	}
 	return rc
@@ -31,11 +37,13 @@ func osGetExclusiveLock(file *os.File, state *LockLevel) _ErrorCode {
 }
 
 func osDowngradeLock(file *os.File, _ LockLevel) _ErrorCode {
-	rc := osLock(file, unix.LOCK_SH|unix.LOCK_NB, _IOERR_RDLOCK)
+	rc := osFlock(file, unix.LOCK_SH|unix.LOCK_NB, _IOERR_RDLOCK)
 	if rc == _BUSY {
-		// The documentation states the lock is upgraded by releasing the previous lock,
-		// then acquiring the new lock.
-		// This is a race, so return IOERR_RDLOCK to ensure the transaction is aborted.
+		// The documentation states that a lock is downgraded by
+		// releasing the previous lock then acquiring the new lock.
+		// Going over the source code of various BSDs, though,
+		// with LOCK_SH|LOCK_NB this should never happen.
+		// Return IOERR_RDLOCK, as BUSY would cause an assert to fail.
 		return _IOERR_RDLOCK
 	}
 	return _OK
@@ -50,12 +58,44 @@ func osReleaseLock(file *os.File, _ LockLevel) _ErrorCode {
 }
 
 func osCheckReservedLock(file *os.File) (bool, _ErrorCode) {
-	// Test the RESERVED lock.
+	// Test the RESERVED lock with fcntl(F_GETLK).
+	// This only works on systems where fcntl and flock are compatible.
+	// However, SQLite only calls this while holding a shared lock,
+	// so the difference is immaterial.
 	lock, rc := osTestLock(file, _RESERVED_BYTE, 1)
 	return lock == unix.F_WRLCK, rc
 }
 
-func osLock(file *os.File, how int, def _ErrorCode) _ErrorCode {
+func osFlock(file *os.File, how int, def _ErrorCode) _ErrorCode {
 	err := unix.Flock(int(file.Fd()), how)
 	return osLockErrorCode(err, def)
 }
+
+func osReadLock(file *os.File, start, len int64) _ErrorCode {
+	return osLock(file, unix.F_RDLCK, start, len, _IOERR_RDLOCK)
+}
+
+func osWriteLock(file *os.File, start, len int64) _ErrorCode {
+	return osLock(file, unix.F_WRLCK, start, len, _IOERR_LOCK)
+}
+
+func osLock(file *os.File, typ int16, start, len int64, def _ErrorCode) _ErrorCode {
+	err := unix.FcntlFlock(file.Fd(), unix.F_SETLK, &unix.Flock_t{
+		Type:  typ,
+		Start: start,
+		Len:   len,
+	})
+	return osLockErrorCode(err, def)
+}
+
+func osUnlock(file *os.File, start, len int64) _ErrorCode {
+	err := unix.FcntlFlock(file.Fd(), unix.F_SETLK, &unix.Flock_t{
+		Type:  unix.F_UNLCK,
+		Start: start,
+		Len:   len,
+	})
+	if err != nil {
+		return _IOERR_UNLOCK
+	}
+	return _OK
+}

vfs/os_darwin.go

@@ -1,4 +1,4 @@
-//go:build !(sqlite3_flock || sqlite3_nosys)
+//go:build !sqlite3_flock
 
 package vfs
 
@@ -56,16 +56,12 @@ func osAllocate(file *os.File, size int64) error {
 	return file.Truncate(size)
 }
 
-func osUnlock(file *os.File, start, len int64) _ErrorCode {
-	err := unix.FcntlFlock(file.Fd(), _F_OFD_SETLK, &unix.Flock_t{
-		Type:  unix.F_UNLCK,
-		Start: start,
-		Len:   len,
-	})
-	if err != nil {
-		return _IOERR_UNLOCK
-	}
-	return _OK
+func osReadLock(file *os.File, start, len int64, timeout time.Duration) _ErrorCode {
+	return osLock(file, unix.F_RDLCK, start, len, timeout, _IOERR_RDLOCK)
+}
+
+func osWriteLock(file *os.File, start, len int64, timeout time.Duration) _ErrorCode {
+	return osLock(file, unix.F_WRLCK, start, len, timeout, _IOERR_LOCK)
 }
 
 func osLock(file *os.File, typ int16, start, len int64, timeout time.Duration, def _ErrorCode) _ErrorCode {
@@ -88,10 +84,14 @@ func osLock(file *os.File, typ int16, start, len int64, timeout time.Duration, d
 	return osLockErrorCode(err, def)
 }
 
-func osReadLock(file *os.File, start, len int64, timeout time.Duration) _ErrorCode {
-	return osLock(file, unix.F_RDLCK, start, len, timeout, _IOERR_RDLOCK)
-}
-
-func osWriteLock(file *os.File, start, len int64, timeout time.Duration) _ErrorCode {
-	return osLock(file, unix.F_WRLCK, start, len, timeout, _IOERR_LOCK)
+func osUnlock(file *os.File, start, len int64) _ErrorCode {
+	err := unix.FcntlFlock(file.Fd(), _F_OFD_SETLK, &unix.Flock_t{
+		Type:  unix.F_UNLCK,
+		Start: start,
+		Len:   len,
+	})
+	if err != nil {
+		return _IOERR_UNLOCK
+	}
+	return _OK
 }

vfs/os_dotlk.go

@@ -7,6 +7,8 @@ import (
 	"io/fs"
 	"os"
 	"sync"
+
+	"github.com/ncruces/go-sqlite3/internal/dotlk"
 )
 
 var (
@@ -28,11 +30,10 @@ func osGetSharedLock(file *os.File) _ErrorCode {
 	name := file.Name()
 	locker := vfsDotLocks[name]
 	if locker == nil {
-		err := os.Mkdir(name+".lock", 0777)
-		if errors.Is(err, fs.ErrExist) {
-			return _BUSY // Another process has the lock.
-		}
-		if err != nil {
+		if err := dotlk.TryLock(name + ".lock"); err != nil {
+			if errors.Is(err, fs.ErrExist) {
+				return _BUSY // Another process has the lock.
+			}
 			return _IOERR_LOCK
 		}
 		locker = &vfsDotLocker{}
@@ -113,8 +114,7 @@ func osReleaseLock(file *os.File, state LockLevel) _ErrorCode {
 	}
 
 	if locker.shared == 1 {
-		err := os.Remove(name + ".lock")
-		if err != nil && !errors.Is(err, fs.ErrNotExist) {
+		if err := dotlk.Unlock(name + ".lock"); err != nil {
 			return _IOERR_UNLOCK
 		}
 		delete(vfsDotLocks, name)

vfs/os_f2fs_linux.go

@@ -1,4 +1,4 @@
-//go:build (amd64 || arm64 || riscv64) && !sqlite3_nosys
+//go:build amd64 || arm64 || riscv64
 
 package vfs
 

vfs/os_linux.go

@@ -1,9 +1,8 @@
-//go:build !(sqlite3_flock || sqlite3_nosys)
+//go:build !sqlite3_flock
 
 package vfs
 
 import (
-	"math/rand"
 	"os"
 	"time"
 
@@ -22,6 +21,30 @@ func osAllocate(file *os.File, size int64) error {
 	return unix.Fallocate(int(file.Fd()), 0, 0, size)
 }
 
+func osReadLock(file *os.File, start, len int64, timeout time.Duration) _ErrorCode {
+	return osLock(file, unix.F_RDLCK, start, len, timeout, _IOERR_RDLOCK)
+}
+
+func osWriteLock(file *os.File, start, len int64, timeout time.Duration) _ErrorCode {
+	return osLock(file, unix.F_WRLCK, start, len, timeout, _IOERR_LOCK)
+}
+
+func osLock(file *os.File, typ int16, start, len int64, timeout time.Duration, def _ErrorCode) _ErrorCode {
+	lock := unix.Flock_t{
+		Type:  typ,
+		Start: start,
+		Len:   len,
+	}
+	var err error
+	switch {
+	case timeout < 0:
+		err = unix.FcntlFlock(file.Fd(), unix.F_OFD_SETLKW, &lock)
+	default:
+		err = unix.FcntlFlock(file.Fd(), unix.F_OFD_SETLK, &lock)
+	}
+	return osLockErrorCode(err, def)
+}
+
 func osUnlock(file *os.File, start, len int64) _ErrorCode {
 	err := unix.FcntlFlock(file.Fd(), unix.F_OFD_SETLK, &unix.Flock_t{
 		Type:  unix.F_UNLCK,
@@ -33,40 +56,3 @@ func osUnlock(file *os.File, start, len int64) _ErrorCode {
 	}
 	return _OK
 }
-
-func osLock(file *os.File, typ int16, start, len int64, timeout time.Duration, def _ErrorCode) _ErrorCode {
-	lock := unix.Flock_t{
-		Type:  typ,
-		Start: start,
-		Len:   len,
-	}
-	var err error
-	switch {
-	case timeout == 0:
-		err = unix.FcntlFlock(file.Fd(), unix.F_OFD_SETLK, &lock)
-	case timeout < 0:
-		err = unix.FcntlFlock(file.Fd(), unix.F_OFD_SETLKW, &lock)
-	default:
-		before := time.Now()
-		for {
-			err = unix.FcntlFlock(file.Fd(), unix.F_OFD_SETLK, &lock)
-			if errno, _ := err.(unix.Errno); errno != unix.EAGAIN {
-				break
-			}
-			if time.Since(before) > timeout {
-				break
-			}
-			const sleepIncrement = 1024*1024 - 1 // power of two, ~1ms
-			time.Sleep(time.Duration(rand.Int63() & sleepIncrement))
-		}
-	}
-	return osLockErrorCode(err, def)
-}
-
-func osReadLock(file *os.File, start, len int64, timeout time.Duration) _ErrorCode {
-	return osLock(file, unix.F_RDLCK, start, len, timeout, _IOERR_RDLOCK)
-}
-
-func osWriteLock(file *os.File, start, len int64, timeout time.Duration) _ErrorCode {
-	return osLock(file, unix.F_WRLCK, start, len, timeout, _IOERR_LOCK)
-}

vfs/os_ofd.go

@@ -1,4 +1,4 @@
-//go:build (linux || darwin) && !(sqlite3_flock || sqlite3_dotlk || sqlite3_nosys)
+//go:build (linux || darwin) && !(sqlite3_flock || sqlite3_dotlk)
 
 package vfs
 

vfs/os_std.go

@@ -1,4 +1,4 @@
-//go:build !unix || sqlite3_nosys
+//go:build !unix
 
 package vfs
 

vfs/os_std_alloc.go

@@ -1,4 +1,4 @@
-//go:build !(linux || darwin) || sqlite3_flock || sqlite3_nosys
+//go:build !(linux || darwin) || sqlite3_flock
 
 package vfs
 

vfs/os_std_atomic.go

@@ -1,4 +1,4 @@
-//go:build !linux || !(amd64 || arm64 || riscv64) || sqlite3_nosys
+//go:build !linux || !(amd64 || arm64 || riscv64)
 
 package vfs
 

vfs/os_std_sync.go

@@ -1,4 +1,4 @@
-//go:build !(linux || darwin) || sqlite3_flock || sqlite3_nosys
+//go:build !(linux || darwin) || sqlite3_flock
 
 package vfs
 

vfs/os_unix.go

@@ -1,4 +1,4 @@
-//go:build unix && !sqlite3_nosys
+//go:build unix
 
 package vfs
 

vfs/os_unix_test.go

@@ -1,4 +1,4 @@
-//go:build unix && !(sqlite3_flock || sqlite3_nosys)
+//go:build unix && !sqlite3_flock
 
 package vfs
 

vfs/os_windows.go

@@ -1,9 +1,8 @@
-//go:build !(sqlite3_dotlk || sqlite3_nosys)
+//go:build !sqlite3_dotlk
 
 package vfs
 
 import (
-	"math/rand"
 	"os"
 	"time"
 
@@ -46,18 +45,22 @@ func osGetExclusiveLock(file *os.File, state *LockLevel) _ErrorCode {
 	osUnlock(file, _SHARED_FIRST, _SHARED_SIZE)
 
 	// Acquire the EXCLUSIVE lock.
-	rc := osWriteLock(file, _SHARED_FIRST, _SHARED_SIZE, time.Millisecond)
+	// Can't wait here, because the file is not OVERLAPPED.
+	rc := osWriteLock(file, _SHARED_FIRST, _SHARED_SIZE, 0)
 
 	if rc != _OK {
 		// Reacquire the SHARED lock.
-		osReadLock(file, _SHARED_FIRST, _SHARED_SIZE, 0)
+		if rc := osReadLock(file, _SHARED_FIRST, _SHARED_SIZE, 0); rc != _OK {
+			// notest // this should never happen
+			return _IOERR_RDLOCK
+		}
 	}
 	return rc
 }
 
 func osDowngradeLock(file *os.File, state LockLevel) _ErrorCode {
 	if state >= LOCK_EXCLUSIVE {
-		// Release the EXCLUSIVE lock.
+		// Release the EXCLUSIVE lock while holding the PENDING lock.
 		osUnlock(file, _SHARED_FIRST, _SHARED_SIZE)
 
 		// Reacquire the SHARED lock.
@@ -78,7 +81,7 @@ func osDowngradeLock(file *os.File, state LockLevel) _ErrorCode {
 }
 
 func osReleaseLock(file *os.File, state LockLevel) _ErrorCode {
-	// Release all locks.
+	// Release all locks, PENDING must be last.
 	if state >= LOCK_RESERVED {
 		osUnlock(file, _RESERVED_BYTE, 1)
 	}
@@ -104,6 +107,27 @@ func osCheckReservedLock(file *os.File) (bool, _ErrorCode) {
 	return false, rc
 }
 
+func osReadLock(file *os.File, start, len uint32, timeout time.Duration) _ErrorCode {
+	return osLock(file, 0, start, len, timeout, _IOERR_RDLOCK)
+}
+
+func osWriteLock(file *os.File, start, len uint32, timeout time.Duration) _ErrorCode {
+	return osLock(file, windows.LOCKFILE_EXCLUSIVE_LOCK, start, len, timeout, _IOERR_LOCK)
+}
+
+func osLock(file *os.File, flags, start, len uint32, timeout time.Duration, def _ErrorCode) _ErrorCode {
+	var err error
+	switch {
+	case timeout == 0:
+		err = osLockEx(file, flags|windows.LOCKFILE_FAIL_IMMEDIATELY, start, len)
+	case timeout < 0:
+		err = osLockEx(file, flags, start, len)
+	default:
+		err = osLockExTimeout(file, flags, start, len, timeout)
+	}
+	return osLockErrorCode(err, def)
+}
+
 func osUnlock(file *os.File, start, len uint32) _ErrorCode {
 	err := windows.UnlockFileEx(windows.Handle(file.Fd()),
 		0, len, 0, &windows.Overlapped{Offset: start})
@@ -116,41 +140,40 @@ func osUnlock(file *os.File, start, len uint32) _ErrorCode {
 	return _OK
 }
 
-func osLock(file *os.File, flags, start, len uint32, timeout time.Duration, def _ErrorCode) _ErrorCode {
-	var err error
-	switch {
-	case timeout == 0:
-		err = osLockEx(file, flags|windows.LOCKFILE_FAIL_IMMEDIATELY, start, len)
-	case timeout < 0:
-		err = osLockEx(file, flags, start, len)
-	default:
-		before := time.Now()
-		for {
-			err = osLockEx(file, flags|windows.LOCKFILE_FAIL_IMMEDIATELY, start, len)
-			if errno, _ := err.(windows.Errno); errno != windows.ERROR_LOCK_VIOLATION {
-				break
-			}
-			if time.Since(before) > timeout {
-				break
-			}
-			const sleepIncrement = 1024*1024 - 1 // power of two, ~1ms
-			time.Sleep(time.Duration(rand.Int63() & sleepIncrement))
-		}
-	}
-	return osLockErrorCode(err, def)
-}
-
 func osLockEx(file *os.File, flags, start, len uint32) error {
 	return windows.LockFileEx(windows.Handle(file.Fd()), flags,
 		0, len, 0, &windows.Overlapped{Offset: start})
 }
 
-func osReadLock(file *os.File, start, len uint32, timeout time.Duration) _ErrorCode {
-	return osLock(file, 0, start, len, timeout, _IOERR_RDLOCK)
-}
+func osLockExTimeout(file *os.File, flags, start, len uint32, timeout time.Duration) error {
+	event, err := windows.CreateEvent(nil, 1, 0, nil)
+	if err != nil {
+		return err
+	}
+	defer windows.CloseHandle(event)
 
-func osWriteLock(file *os.File, start, len uint32, timeout time.Duration) _ErrorCode {
-	return osLock(file, windows.LOCKFILE_EXCLUSIVE_LOCK, start, len, timeout, _IOERR_LOCK)
+	fd := windows.Handle(file.Fd())
+	overlapped := &windows.Overlapped{
+		Offset: start,
+		HEvent: event,
+	}
+
+	err = windows.LockFileEx(fd, flags, 0, len, 0, overlapped)
+	if err != windows.ERROR_IO_PENDING {
+		return err
+	}
+
+	ms := (timeout + time.Millisecond - 1) / time.Millisecond
+	rc, err := windows.WaitForSingleObject(event, uint32(ms))
+	if rc == windows.WAIT_OBJECT_0 {
+		return nil
+	}
+	defer windows.CancelIoEx(fd, overlapped)
+
+	if err != nil {
+		return err
+	}
+	return windows.Errno(rc)
 }
 
 func osLockErrorCode(err error, def _ErrorCode) _ErrorCode {
@@ -162,8 +185,9 @@ func osLockErrorCode(err error, def _ErrorCode) _ErrorCode {
 		switch errno {
 		case
 			windows.ERROR_LOCK_VIOLATION,
+			windows.ERROR_OPERATION_ABORTED,
 			windows.ERROR_IO_PENDING,
-			windows.ERROR_OPERATION_ABORTED:
+			windows.WAIT_TIMEOUT:
 			return _BUSY
 		}
 	}

vfs/readervfs/reader.go

@@ -77,5 +77,5 @@ func (readerFile) SectorSize() int {
 }
 
 func (readerFile) DeviceCharacteristics() vfs.DeviceCharacteristic {
-	return vfs.IOCAP_IMMUTABLE
+	return vfs.IOCAP_IMMUTABLE | vfs.IOCAP_SUBPAGE_READ
 }

vfs/shm.go

@@ -1,4 +1,4 @@
-//go:build ((linux || darwin || windows || freebsd || openbsd || netbsd || dragonfly || illumos) && (386 || arm || amd64 || arm64 || riscv64 || ppc64le) && !sqlite3_nosys) || sqlite3_flock || sqlite3_dotlk
+//go:build ((linux || darwin || windows || freebsd || openbsd || netbsd || dragonfly || illumos) && (386 || arm || amd64 || arm64 || riscv64 || ppc64le)) || sqlite3_flock || sqlite3_dotlk
 
 package vfs
 

vfs/shm_bsd.go

@@ -1,10 +1,12 @@
-//go:build ((freebsd || openbsd || netbsd || dragonfly || illumos) && (386 || arm || amd64 || arm64 || riscv64 || ppc64le) && !(sqlite3_dotlk || sqlite3_nosys)) || sqlite3_flock
+//go:build ((freebsd || openbsd || netbsd || dragonfly || illumos) && (386 || arm || amd64 || arm64 || riscv64 || ppc64le) && !sqlite3_dotlk) || sqlite3_flock
 
 package vfs
 
 import (
 	"context"
+	"errors"
 	"io"
+	"io/fs"
 	"os"
 	"sync"
 
@@ -14,52 +16,52 @@ import (
 	"github.com/ncruces/go-sqlite3/internal/util"
 )
 
-type vfsShmFile struct {
+type vfsShmParent struct {
 	*os.File
 	info os.FileInfo
 
-	refs int // +checklocks:vfsShmFilesMtx
+	refs int // +checklocks:vfsShmListMtx
 
-	lock [_SHM_NLOCK]int16 // +checklocks:Mutex
+	lock [_SHM_NLOCK]int8 // +checklocks:Mutex
 	sync.Mutex
 }
 
 var (
-	// +checklocks:vfsShmFilesMtx
-	vfsShmFiles    []*vfsShmFile
-	vfsShmFilesMtx sync.Mutex
+	// +checklocks:vfsShmListMtx
+	vfsShmList    []*vfsShmParent
+	vfsShmListMtx sync.Mutex
 )
 
 type vfsShm struct {
-	*vfsShmFile
+	*vfsShmParent
 	path    string
 	lock    [_SHM_NLOCK]bool
 	regions []*util.MappedRegion
 }
 
 func (s *vfsShm) Close() error {
-	if s.vfsShmFile == nil {
+	if s.vfsShmParent == nil {
 		return nil
 	}
 
-	vfsShmFilesMtx.Lock()
-	defer vfsShmFilesMtx.Unlock()
+	vfsShmListMtx.Lock()
+	defer vfsShmListMtx.Unlock()
 
 	// Unlock everything.
 	s.shmLock(0, _SHM_NLOCK, _SHM_UNLOCK)
 
 	// Decrease reference count.
-	if s.vfsShmFile.refs > 0 {
-		s.vfsShmFile.refs--
-		s.vfsShmFile = nil
+	if s.vfsShmParent.refs > 0 {
+		s.vfsShmParent.refs--
+		s.vfsShmParent = nil
 		return nil
 	}
 
 	err := s.File.Close()
-	for i, g := range vfsShmFiles {
-		if g == s.vfsShmFile {
-			vfsShmFiles[i] = nil
-			s.vfsShmFile = nil
+	for i, g := range vfsShmList {
+		if g == s.vfsShmParent {
+			vfsShmList[i] = nil
+			s.vfsShmParent = nil
 			return err
 		}
 	}
@@ -67,58 +69,76 @@ func (s *vfsShm) Close() error {
 }
 
 func (s *vfsShm) shmOpen() _ErrorCode {
-	if s.vfsShmFile != nil {
+	if s.vfsShmParent != nil {
 		return _OK
 	}
 
-	// Always open file read-write, as it will be shared.
-	f, err := os.OpenFile(s.path,
-		unix.O_RDWR|unix.O_CREAT|unix.O_NOFOLLOW, 0666)
-	if err != nil {
-		return _CANTOPEN
-	}
-	// Closes file if it's not nil.
+	var f *os.File
+	// Close file on error.
+	// Keep this here to avoid confusing checklocks.
 	defer func() { f.Close() }()
 
-	fi, err := f.Stat()
-	if err != nil {
+	vfsShmListMtx.Lock()
+	defer vfsShmListMtx.Unlock()
+
+	// Stat file without opening it.
+	// Closing it would release all POSIX locks on it.
+	fi, err := os.Stat(s.path)
+	if err != nil && !errors.Is(err, fs.ErrNotExist) {
 		return _IOERR_FSTAT
 	}
 
-	vfsShmFilesMtx.Lock()
-	defer vfsShmFilesMtx.Unlock()
-
 	// Find a shared file, increase the reference count.
-	for _, g := range vfsShmFiles {
+	for _, g := range vfsShmList {
 		if g != nil && os.SameFile(fi, g.info) {
-			s.vfsShmFile = g
+			s.vfsShmParent = g
 			g.refs++
 			return _OK
 		}
 	}
 
-	// Lock and truncate the file.
-	// The lock is only released by closing the file.
-	if rc := osLock(f, unix.LOCK_EX|unix.LOCK_NB, _IOERR_LOCK); rc != _OK {
+	// Always open file read-write, as it will be shared.
+	f, err = os.OpenFile(s.path,
+		os.O_RDWR|os.O_CREATE|_O_NOFOLLOW, 0666)
+	if err != nil {
+		return _CANTOPEN
+	}
+
+	// Dead man's switch.
+	if lock, rc := osTestLock(f, _SHM_DMS, 1); rc != _OK {
+		return _IOERR_LOCK
+	} else if lock == unix.F_WRLCK {
+		return _BUSY
+	} else if lock == unix.F_UNLCK {
+		if rc := osWriteLock(f, _SHM_DMS, 1); rc != _OK {
+			return rc
+		}
+		if err := f.Truncate(0); err != nil {
+			return _IOERR_SHMOPEN
+		}
+	}
+	if rc := osReadLock(f, _SHM_DMS, 1); rc != _OK {
 		return rc
 	}
-	if err := f.Truncate(0); err != nil {
-		return _IOERR_SHMOPEN
+
+	fi, err = f.Stat()
+	if err != nil {
+		return _IOERR_FSTAT
 	}
 
 	// Add the new shared file.
-	s.vfsShmFile = &vfsShmFile{
+	s.vfsShmParent = &vfsShmParent{
 		File: f,
 		info: fi,
 	}
 	f = nil // Don't close the file.
-	for i, g := range vfsShmFiles {
+	for i, g := range vfsShmList {
 		if g == nil {
-			vfsShmFiles[i] = s.vfsShmFile
+			vfsShmList[i] = s.vfsShmParent
 			return _OK
 		}
 	}
-	vfsShmFiles = append(vfsShmFiles, s.vfsShmFile)
+	vfsShmList = append(vfsShmList, s.vfsShmParent)
 	return _OK
 }
 
@@ -158,56 +178,45 @@ func (s *vfsShm) shmLock(offset, n int32, flags _ShmFlag) _ErrorCode {
 	s.Lock()
 	defer s.Unlock()
 
+	// Check if we could obtain/release the lock locally.
+	rc := s.shmMemLock(offset, n, flags)
+	if rc != _OK {
+		return rc
+	}
+
+	// Obtain/release the appropriate file locks.
 	switch {
 	case flags&_SHM_UNLOCK != 0:
-		for i := offset; i < offset+n; i++ {
-			if s.lock[i] {
-				if s.vfsShmFile.lock[i] == 0 {
-					panic(util.AssertErr())
+		begin, end := offset, offset+n
+		for i := begin; i < end; i++ {
+			if s.vfsShmParent.lock[i] != 0 {
+				if i > begin {
+					rc |= osUnlock(s.File, _SHM_BASE+int64(begin), int64(i-begin))
 				}
-				if s.vfsShmFile.lock[i] <= 0 {
-					s.vfsShmFile.lock[i] = 0
-				} else {
-					s.vfsShmFile.lock[i]--
-				}
-				s.lock[i] = false
+				begin = i + 1
 			}
 		}
+		if end > begin {
+			rc |= osUnlock(s.File, _SHM_BASE+int64(begin), int64(end-begin))
+		}
+		return rc
 	case flags&_SHM_SHARED != 0:
-		for i := offset; i < offset+n; i++ {
-			if s.lock[i] {
-				panic(util.AssertErr())
-			}
-			if s.vfsShmFile.lock[i]+1 <= 0 {
-				return _BUSY
-			}
-		}
-		for i := offset; i < offset+n; i++ {
-			s.vfsShmFile.lock[i]++
-			s.lock[i] = true
-		}
+		rc = osReadLock(s.File, _SHM_BASE+int64(offset), int64(n))
 	case flags&_SHM_EXCLUSIVE != 0:
-		for i := offset; i < offset+n; i++ {
-			if s.lock[i] {
-				panic(util.AssertErr())
-			}
-			if s.vfsShmFile.lock[i] != 0 {
-				return _BUSY
-			}
-		}
-		for i := offset; i < offset+n; i++ {
-			s.vfsShmFile.lock[i] = -1
-			s.lock[i] = true
-		}
+		rc = osWriteLock(s.File, _SHM_BASE+int64(offset), int64(n))
 	default:
 		panic(util.AssertErr())
 	}
 
-	return _OK
+	// Release the local lock we had acquired.
+	if rc != _OK {
+		s.shmMemLock(offset, n, flags^(_SHM_UNLOCK|_SHM_LOCK))
+	}
+	return rc
 }
 
 func (s *vfsShm) shmUnmap(delete bool) {
-	if s.vfsShmFile == nil {
+	if s.vfsShmParent == nil {
 		return
 	}
 

vfs/shm_copy.go

@@ -1,4 +1,4 @@
-//go:build (windows && (386 || arm || amd64 || arm64 || riscv64 || ppc64le) && !sqlite3_nosys) || sqlite3_dotlk
+//go:build (windows && (386 || arm || amd64 || arm64 || riscv64 || ppc64le)) || sqlite3_dotlk
 
 package vfs
 
@@ -13,7 +13,7 @@ const (
 	_WALINDEX_PGSZ     = 32768
 )
 
-// This looks like a safe way of keeping the WAL-index in sync.
+// This seems a safe way of keeping the WAL-index in sync.
 //
 // The WAL-index file starts with a header,
 // and the index doesn't meaningfully change if the header doesn't change.
@@ -27,12 +27,15 @@ const (
 //
 // Since all the data is either redundant+checksummed,
 // 4 byte aligned, or modified under an exclusive lock,
-// the copies below should correctly keep copies in sync.
+// the copies below should correctly keep memory in sync.
 //
 // https://sqlite.org/walformat.html#the_wal_index_file_format
 
-func (s *vfsShm) shmAcquire() {
-	if len(s.ptrs) == 0 || shmUnmodified(s.shadow[0][:], s.shared[0][:]) {
+func (s *vfsShm) shmAcquire(ptr *_ErrorCode) {
+	if ptr != nil && *ptr != _OK {
+		return
+	}
+	if len(s.ptrs) == 0 || shmEqual(s.shadow[0][:], s.shared[0][:]) {
 		return
 	}
 	// Copies modified words from shared to private memory.
@@ -50,7 +53,7 @@ func (s *vfsShm) shmAcquire() {
 }
 
 func (s *vfsShm) shmRelease() {
-	if len(s.ptrs) == 0 || shmUnmodified(s.shadow[0][:], util.View(s.mod, s.ptrs[0], _WALINDEX_HDR_SIZE)) {
+	if len(s.ptrs) == 0 || shmEqual(s.shadow[0][:], util.View(s.mod, s.ptrs[0], _WALINDEX_HDR_SIZE)) {
 		return
 	}
 	// Copies modified words from private to shared memory.
@@ -69,7 +72,7 @@ func (s *vfsShm) shmRelease() {
 
 func (s *vfsShm) shmBarrier() {
 	s.Lock()
-	s.shmAcquire()
+	s.shmAcquire(nil)
 	s.shmRelease()
 	s.Unlock()
 }
@@ -79,6 +82,6 @@ func shmPage(s []byte) *[_WALINDEX_PGSZ / 4]uint32 {
 	return (*[_WALINDEX_PGSZ / 4]uint32)(unsafe.Slice(p, _WALINDEX_PGSZ/4))
 }
 
-func shmUnmodified(v1, v2 []byte) bool {
+func shmEqual(v1, v2 []byte) bool {
 	return *(*[_WALINDEX_HDR_SIZE]byte)(v1[:]) == *(*[_WALINDEX_HDR_SIZE]byte)(v2[:])
 }

vfs/shm_dotlk.go

@@ -6,29 +6,30 @@ import (
 	"context"
 	"errors"
 	"io/fs"
-	"os"
 	"sync"
 
-	"github.com/ncruces/go-sqlite3/internal/util"
 	"github.com/tetratelabs/wazero/api"
+
+	"github.com/ncruces/go-sqlite3/internal/dotlk"
+	"github.com/ncruces/go-sqlite3/internal/util"
 )
 
-type vfsShmBuffer struct {
+type vfsShmParent struct {
 	shared [][_WALINDEX_PGSZ]byte
-	refs   int // +checklocks:vfsShmBuffersMtx
+	refs   int // +checklocks:vfsShmListMtx
 
-	lock [_SHM_NLOCK]int16 // +checklocks:Mutex
+	lock [_SHM_NLOCK]int8 // +checklocks:Mutex
 	sync.Mutex
 }
 
 var (
-	// +checklocks:vfsShmBuffersMtx
-	vfsShmBuffers    = map[string]*vfsShmBuffer{}
-	vfsShmBuffersMtx sync.Mutex
+	// +checklocks:vfsShmListMtx
+	vfsShmList    = map[string]*vfsShmParent{}
+	vfsShmListMtx sync.Mutex
 )
 
 type vfsShm struct {
-	*vfsShmBuffer
+	*vfsShmParent
 	mod    api.Module
 	alloc  api.Function
 	free   api.Function
@@ -40,50 +41,48 @@ type vfsShm struct {
 }
 
 func (s *vfsShm) Close() error {
-	if s.vfsShmBuffer == nil {
+	if s.vfsShmParent == nil {
 		return nil
 	}
 
-	vfsShmBuffersMtx.Lock()
-	defer vfsShmBuffersMtx.Unlock()
+	vfsShmListMtx.Lock()
+	defer vfsShmListMtx.Unlock()
 
 	// Unlock everything.
 	s.shmLock(0, _SHM_NLOCK, _SHM_UNLOCK)
 
 	// Decrease reference count.
-	if s.vfsShmBuffer.refs > 0 {
-		s.vfsShmBuffer.refs--
-		s.vfsShmBuffer = nil
+	if s.vfsShmParent.refs > 0 {
+		s.vfsShmParent.refs--
+		s.vfsShmParent = nil
 		return nil
 	}
 
-	err := os.Remove(s.path)
-	if err != nil && !errors.Is(err, fs.ErrNotExist) {
+	if err := dotlk.Unlock(s.path); err != nil {
 		return _IOERR_UNLOCK
 	}
-	delete(vfsShmBuffers, s.path)
-	s.vfsShmBuffer = nil
+	delete(vfsShmList, s.path)
+	s.vfsShmParent = nil
 	return nil
 }
 
 func (s *vfsShm) shmOpen() _ErrorCode {
-	if s.vfsShmBuffer != nil {
+	if s.vfsShmParent != nil {
 		return _OK
 	}
 
-	vfsShmBuffersMtx.Lock()
-	defer vfsShmBuffersMtx.Unlock()
+	vfsShmListMtx.Lock()
+	defer vfsShmListMtx.Unlock()
 
 	// Find a shared buffer, increase the reference count.
-	if g, ok := vfsShmBuffers[s.path]; ok {
-		s.vfsShmBuffer = g
+	if g, ok := vfsShmList[s.path]; ok {
+		s.vfsShmParent = g
 		g.refs++
 		return _OK
 	}
 
-	// Create a directory on disk to ensure only this process
-	// uses this path to register a shared memory.
-	err := os.Mkdir(s.path, 0777)
+	// Dead man's switch.
+	err := dotlk.LockShm(s.path)
 	if errors.Is(err, fs.ErrExist) {
 		return _BUSY
 	}
@@ -92,8 +91,8 @@ func (s *vfsShm) shmOpen() _ErrorCode {
 	}
 
 	// Add the new shared buffer.
-	s.vfsShmBuffer = &vfsShmBuffer{}
-	vfsShmBuffers[s.path] = s.vfsShmBuffer
+	s.vfsShmParent = &vfsShmParent{}
+	vfsShmList[s.path] = s.vfsShmParent
 	return _OK
 }
 
@@ -112,7 +111,7 @@ func (s *vfsShm) shmMap(ctx context.Context, mod api.Module, id, size int32, ext
 
 	s.Lock()
 	defer s.Unlock()
-	defer s.shmAcquire()
+	defer s.shmAcquire(nil)
 
 	// Extend shared memory.
 	if int(id) >= len(s.shared) {
@@ -125,7 +124,6 @@ func (s *vfsShm) shmMap(ctx context.Context, mod api.Module, id, size int32, ext
 	// Allocate shadow memory.
 	if int(id) >= len(s.shadow) {
 		s.shadow = append(s.shadow, make([][_WALINDEX_PGSZ]byte, int(id)-len(s.shadow)+1)...)
-		s.shadow[0][4] = 1 // force invalidation
 	}
 
 	// Allocate local memory.
@@ -141,70 +139,26 @@ func (s *vfsShm) shmMap(ctx context.Context, mod api.Module, id, size int32, ext
 		s.ptrs = append(s.ptrs, uint32(s.stack[0]))
 	}
 
+	s.shadow[0][4] = 1
 	return s.ptrs[id], _OK
 }
 
-func (s *vfsShm) shmLock(offset, n int32, flags _ShmFlag) _ErrorCode {
+func (s *vfsShm) shmLock(offset, n int32, flags _ShmFlag) (rc _ErrorCode) {
 	s.Lock()
 	defer s.Unlock()
 
 	switch {
 	case flags&_SHM_LOCK != 0:
-		defer s.shmAcquire()
+		defer s.shmAcquire(&rc)
 	case flags&_SHM_EXCLUSIVE != 0:
 		s.shmRelease()
 	}
 
-	switch {
-	case flags&_SHM_UNLOCK != 0:
-		for i := offset; i < offset+n; i++ {
-			if s.lock[i] {
-				if s.vfsShmBuffer.lock[i] == 0 {
-					panic(util.AssertErr())
-				}
-				if s.vfsShmBuffer.lock[i] <= 0 {
-					s.vfsShmBuffer.lock[i] = 0
-				} else {
-					s.vfsShmBuffer.lock[i]--
-				}
-				s.lock[i] = false
-			}
-		}
-	case flags&_SHM_SHARED != 0:
-		for i := offset; i < offset+n; i++ {
-			if s.lock[i] {
-				panic(util.AssertErr())
-			}
-			if s.vfsShmBuffer.lock[i]+1 <= 0 {
-				return _BUSY
-			}
-		}
-		for i := offset; i < offset+n; i++ {
-			s.vfsShmBuffer.lock[i]++
-			s.lock[i] = true
-		}
-	case flags&_SHM_EXCLUSIVE != 0:
-		for i := offset; i < offset+n; i++ {
-			if s.lock[i] {
-				panic(util.AssertErr())
-			}
-			if s.vfsShmBuffer.lock[i] != 0 {
-				return _BUSY
-			}
-		}
-		for i := offset; i < offset+n; i++ {
-			s.vfsShmBuffer.lock[i] = -1
-			s.lock[i] = true
-		}
-	default:
-		panic(util.AssertErr())
-	}
-
-	return _OK
+	return s.shmMemLock(offset, n, flags)
 }
 
 func (s *vfsShm) shmUnmap(delete bool) {
-	if s.vfsShmBuffer == nil {
+	if s.vfsShmParent == nil {
 		return
 	}
 	defer s.Close()

vfs/shm_memlk.go

@@ -0,0 +1,53 @@
+//go:build ((freebsd || openbsd || netbsd || dragonfly || illumos) && (386 || arm || amd64 || arm64 || riscv64 || ppc64le)) || sqlite3_flock || sqlite3_dotlk
+
+package vfs
+
+import "github.com/ncruces/go-sqlite3/internal/util"
+
+// +checklocks:s.Mutex
+func (s *vfsShm) shmMemLock(offset, n int32, flags _ShmFlag) _ErrorCode {
+	switch {
+	case flags&_SHM_UNLOCK != 0:
+		for i := offset; i < offset+n; i++ {
+			if s.lock[i] {
+				if s.vfsShmParent.lock[i] <= 0 {
+					s.vfsShmParent.lock[i] = 0
+				} else {
+					s.vfsShmParent.lock[i]--
+				}
+				s.lock[i] = false
+			}
+		}
+	case flags&_SHM_SHARED != 0:
+		for i := offset; i < offset+n; i++ {
+			if !s.lock[i] &&
+				s.vfsShmParent.lock[i]+1 <= 0 {
+				return _BUSY
+			}
+		}
+		for i := offset; i < offset+n; i++ {
+			if !s.lock[i] {
+				s.vfsShmParent.lock[i]++
+				s.lock[i] = true
+			}
+		}
+	case flags&_SHM_EXCLUSIVE != 0:
+		for i := offset; i < offset+n; i++ {
+			if s.lock[i] {
+				// SQLite never requests an exclusive lock that it already holds.
+				panic(util.AssertErr())
+			}
+			if s.vfsShmParent.lock[i] != 0 {
+				return _BUSY
+			}
+		}
+		for i := offset; i < offset+n; i++ {
+			s.vfsShmParent.lock[i] = -1
+			s.lock[i] = true
+		}
+	default:
+		panic(util.AssertErr())
+	}
+
+	return _OK
+}

vfs/shm_ofd.go

@@ -1,4 +1,4 @@
-//go:build (linux || darwin) && (386 || arm || amd64 || arm64 || riscv64 || ppc64le) && !(sqlite3_flock || sqlite3_dotlk || sqlite3_nosys)
+//go:build (linux || darwin) && (386 || arm || amd64 || arm64 || riscv64 || ppc64le) && !(sqlite3_flock || sqlite3_dotlk)
 
 package vfs
 
@@ -20,6 +20,7 @@ type vfsShm struct {
 	path     string
 	regions  []*util.MappedRegion
 	readOnly bool
+	fileLock bool
 	blocking bool
 	sync.Mutex
 }
@@ -29,10 +30,10 @@ var _ blockingSharedMemory = &vfsShm{}
 func (s *vfsShm) shmOpen() _ErrorCode {
 	if s.File == nil {
 		f, err := os.OpenFile(s.path,
-			unix.O_RDWR|unix.O_CREAT|unix.O_NOFOLLOW, 0666)
+			os.O_RDWR|os.O_CREATE|_O_NOFOLLOW, 0666)
 		if err != nil {
 			f, err = os.OpenFile(s.path,
-				unix.O_RDONLY|unix.O_CREAT|unix.O_NOFOLLOW, 0666)
+				os.O_RDONLY|os.O_CREATE|_O_NOFOLLOW, 0666)
 			s.readOnly = true
 		}
 		if err != nil {
@@ -40,6 +41,9 @@ func (s *vfsShm) shmOpen() _ErrorCode {
 		}
 		s.File = f
 	}
+	if s.fileLock {
+		return _OK
+	}
 
 	// Dead man's switch.
 	if lock, rc := osTestLock(s.File, _SHM_DMS, 1); rc != _OK {
@@ -64,7 +68,9 @@ func (s *vfsShm) shmOpen() _ErrorCode {
 			return _IOERR_SHMOPEN
 		}
 	}
-	return osReadLock(s.File, _SHM_DMS, 1, time.Millisecond)
+	rc := osReadLock(s.File, _SHM_DMS, 1, time.Millisecond)
+	s.fileLock = rc == _OK
+	return rc
 }
 
 func (s *vfsShm) shmMap(ctx context.Context, mod api.Module, id, size int32, extend bool) (uint32, _ErrorCode) {
@@ -104,7 +110,12 @@ func (s *vfsShm) shmMap(ctx context.Context, mod api.Module, id, size int32, ext
 
 func (s *vfsShm) shmLock(offset, n int32, flags _ShmFlag) _ErrorCode {
 	// Argument check.
-	if n <= 0 || offset < 0 || offset+n > _SHM_NLOCK {
+	switch {
+	case n <= 0:
+		panic(util.AssertErr())
+	case offset < 0 || offset+n > _SHM_NLOCK:
+		panic(util.AssertErr())
+	case n != 1 && flags&_SHM_EXCLUSIVE == 0:
 		panic(util.AssertErr())
 	}
 	switch flags {
@@ -117,9 +128,6 @@ func (s *vfsShm) shmLock(offset, n int32, flags _ShmFlag) _ErrorCode {
 	default:
 		panic(util.AssertErr())
 	}
-	if n != 1 && flags&_SHM_EXCLUSIVE == 0 {
-		panic(util.AssertErr())
-	}
 
 	var timeout time.Duration
 	if s.blocking {

vfs/shm_other.go

@@ -1,4 +1,4 @@
-//go:build !(((linux || darwin || windows || freebsd || openbsd || netbsd || dragonfly || illumos) && (386 || arm || amd64 || arm64 || riscv64 || ppc64le) && !sqlite3_nosys) || sqlite3_flock || sqlite3_dotlk)
+//go:build !(((linux || darwin || windows || freebsd || openbsd || netbsd || dragonfly || illumos) && (386 || arm || amd64 || arm64 || riscv64 || ppc64le)) || sqlite3_flock || sqlite3_dotlk)
 
 package vfs
 

vfs/shm_windows.go

@@ -1,4 +1,4 @@
-//go:build (386 || arm || amd64 || arm64 || riscv64 || ppc64le) && !(sqlite3_dotlk || sqlite3_nosys)
+//go:build (386 || arm || amd64 || arm64 || riscv64 || ppc64le) && !sqlite3_dotlk
 
 package vfs
 
@@ -7,6 +7,7 @@ import (
 	"io"
 	"os"
 	"sync"
+	"syscall"
 	"time"
 
 	"github.com/tetratelabs/wazero/api"
@@ -27,6 +28,7 @@ type vfsShm struct {
 	shadow   [][_WALINDEX_PGSZ]byte
 	ptrs     []uint32
 	stack    [1]uint64
+	fileLock bool
 	blocking bool
 	sync.Mutex
 }
@@ -46,12 +48,16 @@ func (s *vfsShm) Close() error {
 
 func (s *vfsShm) shmOpen() _ErrorCode {
 	if s.File == nil {
-		f, err := osutil.OpenFile(s.path, os.O_RDWR|os.O_CREATE, 0666)
+		f, err := osutil.OpenFile(s.path,
+			os.O_RDWR|os.O_CREATE|syscall.O_NONBLOCK, 0666)
 		if err != nil {
 			return _CANTOPEN
 		}
 		s.File = f
 	}
+	if s.fileLock {
+		return _OK
+	}
 
 	// Dead man's switch.
 	if rc := osWriteLock(s.File, _SHM_DMS, 1, 0); rc == _OK {
@@ -61,10 +67,12 @@ func (s *vfsShm) shmOpen() _ErrorCode {
 			return _IOERR_SHMOPEN
 		}
 	}
-	return osReadLock(s.File, _SHM_DMS, 1, time.Millisecond)
+	rc := osReadLock(s.File, _SHM_DMS, 1, time.Millisecond)
+	s.fileLock = rc == _OK
+	return rc
 }
 
-func (s *vfsShm) shmMap(ctx context.Context, mod api.Module, id, size int32, extend bool) (uint32, _ErrorCode) {
+func (s *vfsShm) shmMap(ctx context.Context, mod api.Module, id, size int32, extend bool) (_ uint32, rc _ErrorCode) {
 	// Ensure size is a multiple of the OS page size.
 	if size != _WALINDEX_PGSZ || (windows.Getpagesize()-1)&_WALINDEX_PGSZ != 0 {
 		return 0, _IOERR_SHMMAP
@@ -78,7 +86,7 @@ func (s *vfsShm) shmMap(ctx context.Context, mod api.Module, id, size int32, ext
 		return 0, rc
 	}
 
-	defer s.shmAcquire()
+	defer s.shmAcquire(&rc)
 
 	// Check if file is big enough.
 	o, err := s.Seek(0, io.SeekEnd)
@@ -107,7 +115,6 @@ func (s *vfsShm) shmMap(ctx context.Context, mod api.Module, id, size int32, ext
 	// Allocate shadow memory.
 	if int(id) >= len(s.shadow) {
 		s.shadow = append(s.shadow, make([][_WALINDEX_PGSZ]byte, int(id)-len(s.shadow)+1)...)
-		s.shadow[0][4] = 1 // force invalidation
 	}
 
 	// Allocate local memory.
@@ -123,22 +130,23 @@ func (s *vfsShm) shmMap(ctx context.Context, mod api.Module, id, size int32, ext
 		s.ptrs = append(s.ptrs, uint32(s.stack[0]))
 	}
 
+	s.shadow[0][4] = 1
 	return s.ptrs[id], _OK
 }
 
-func (s *vfsShm) shmLock(offset, n int32, flags _ShmFlag) _ErrorCode {
-	switch {
-	case flags&_SHM_LOCK != 0:
-		defer s.shmAcquire()
-	case flags&_SHM_EXCLUSIVE != 0:
-		s.shmRelease()
-	}
-
+func (s *vfsShm) shmLock(offset, n int32, flags _ShmFlag) (rc _ErrorCode) {
 	var timeout time.Duration
 	if s.blocking {
 		timeout = time.Millisecond
 	}
 
+	switch {
+	case flags&_SHM_LOCK != 0:
+		defer s.shmAcquire(&rc)
+	case flags&_SHM_EXCLUSIVE != 0:
+		s.shmRelease()
+	}
+
 	switch {
 	case flags&_SHM_UNLOCK != 0:
 		return osUnlock(s.File, _SHM_BASE+uint32(offset), uint32(n))

vfs/tests/mptest/testdata/mptest.wasm.bz2

@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:4a2ed4f7fe323843e78c59a23e0bd078d807745a3e6276a9862ff08bb7bdac18
-size 480769
+oid sha256:e20f37d94223a88d8f94b3a20177c0fbf53392df2f9c59a28cc7f1f2b5d3de81
+size 477370

vfs/tests/speedtest1/testdata/speedtest1.wasm.bz2

@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:98abb49f1b6acf5398c08556571d44acdc7258484e510b3f8c7a19ee42b5821c
-size 493373
+oid sha256:eebe395695c739a24e9cded13553b97d232eb268a5bc36f10f27cc13945e78cd
+size 491003

vfs/xts/xts.go

@@ -194,11 +194,13 @@ func (x *xtsFile) WriteAt(p []byte, off int64) (n int, err error) {
 func (x *xtsFile) DeviceCharacteristics() vfs.DeviceCharacteristic {
 	var _ [0]struct{} = [sectorSize - 512]struct{}{} // Ensure sectorSize is 512.
 	return x.File.DeviceCharacteristics() & (0 |
-		// The only safe flags are these:
+		// These flags are safe:
 		vfs.IOCAP_ATOMIC512 |
-		vfs.IOCAP_UNDELETABLE_WHEN_OPEN |
 		vfs.IOCAP_IMMUTABLE |
-		vfs.IOCAP_BATCH_ATOMIC)
+		vfs.IOCAP_SEQUENTIAL |
+		vfs.IOCAP_SUBPAGE_READ |
+		vfs.IOCAP_BATCH_ATOMIC |
+		vfs.IOCAP_UNDELETABLE_WHEN_OPEN)
 }
 
 func (x *xtsFile) SectorSize() int {