From 0bdce8aa689706a9c28f97eb5d3f2453d1f1ecbf Mon Sep 17 00:00:00 2001
From: Nuno Cruces <ncruces@users.noreply.github.com>
Date: Thu, 12 Jun 2025 12:32:44 +0100
Subject: [PATCH] Avoid overflow.

---
 sqlite3/libc/libc.wasm | Bin 6300 -> 6300 bytes
 sqlite3/libc/libc.wat  |   6 +++---
 sqlite3/libc/string.h  |   6 +++++-
 sqlite3/libc/strings.h |   1 +
 4 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/sqlite3/libc/libc.wasm b/sqlite3/libc/libc.wasm
index 821c6985bd441fe9ad1f23bbaf1f1b51db7f17f8..70fa201c6232a09d77a7c90c827ec84d347ef095 100755
GIT binary patch
delta 17
YcmbPZILC0qR1OyAYz4;6GdY+A05l~8;s5{u

delta 17
YcmbPZILC0qR1OwK1?H^HGdY+A05fI;;Q#;t

diff --git a/sqlite3/libc/libc.wat b/sqlite3/libc/libc.wat
index 2188a97..2349c96 100644
--- a/sqlite3/libc/libc.wat
+++ b/sqlite3/libc/libc.wat
@@ -1325,11 +1325,11 @@
    )
    (i32.const 0)
    (i32.le_u
-    (local.get $0)
-    (i32.add
-     (local.get $1)
+    (i32.sub
+     (local.get $0)
      (local.get $3)
     )
+    (local.get $1)
    )
   )
  )
diff --git a/sqlite3/libc/string.h b/sqlite3/libc/string.h
index a040674..37c8718 100644
--- a/sqlite3/libc/string.h
+++ b/sqlite3/libc/string.h
@@ -113,7 +113,7 @@ void *memchr(const void *v, int c, size_t n) {
         // That's a match, unless it is beyond the end of the object.
         // Recall that we decremented n, so less-than-or-equal-to is correct.
         size_t ctz = __builtin_ctz(mask);
-        return ctz <= n + align ? (char *)w + ctz : NULL;
+        return ctz - align <= n ? (char *)w + ctz : NULL;
       }
     }
     // Decrement n; if it overflows we're done.
@@ -166,6 +166,8 @@ size_t strlen(const char *s) {
       // At least one bit will be set, unless we cleared them.
       // Knowing this helps the compiler.
       __builtin_assume(mask || align);
+      // If the mask is zero because of alignment,
+      // it's as if we didn't find anything.
       if (mask) {
         // Find the offset of the first one bit (little-endian).
         return (char *)w - s + __builtin_ctz(mask);
@@ -280,6 +282,8 @@ static char *__strchrnul(const char *s, int c) {
       // At least one bit will be set, unless we cleared them.
       // Knowing this helps the compiler.
       __builtin_assume(mask || align);
+      // If the mask is zero because of alignment,
+      // it's as if we didn't find anything.
       if (mask) {
         // Find the offset of the first one bit (little-endian).
         return (char *)w + __builtin_ctz(mask);
diff --git a/sqlite3/libc/strings.h b/sqlite3/libc/strings.h
index 4cd92c9..4f44eda 100644
--- a/sqlite3/libc/strings.h
+++ b/sqlite3/libc/strings.h
@@ -57,6 +57,7 @@ int bcmp(const void *v1, const void *v2, size_t n) {
 
 #endif  // __OPTIMIZE_SIZE__
 
+__attribute__((always_inline))
 static v128_t __tolower8x16(v128_t v) {
   __i8x16 i = v;
   i = i + wasm_i8x16_splat(INT8_MAX - ('Z'));