os_win.c: fix #221 WAL STATUS_IN_PAGE_ERROR crash on Windows without SEH

CHANGELOG.md

@@ -1,5 +1,8 @@
 # Changelog
 
+ - Unreleased:
+     - Fix crash on Windows when accessing truncated *-shm mapping in WAL mode (#221). Emulate SQLite SEH handling via runtime/debug.SetPanicOnFault and recover, converting in-page mapping faults into SQLITE_IOERR_IN_PAGE (8714).
+
 Entries for v1.38.1 through v1.44.1 and for v1.49.1 were added on 2026-09-05, reconstructed from the git history and the merge requests they cite; they were missing at release time.
 
  - 2026-09-05 v1.59.0:

issue221_windows_test.go

@@ -0,0 +1,20 @@
+// Copyright 2026 The Sqlite Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build windows
+
+package sqlite_test
+
+import (
+	"testing"
+)
+
+func TestIssue221_Windows(t *testing.T) {
+	// The full two-tier test with unencapsulated engine negative witness lives in
+	// modernc.org/libsqlite3 (issue221_windows_test.go), which owns the SQLite amalgamation,
+	// C patch (internal/sqlite_issue221.patch), and transpiler configuration (generator.go).
+	// The vendored code in modernc.org/sqlite/lib will gain active SEH call sites once
+	// upstream builders execute 'make vendor' from the patched libsqlite3.
+	t.Skip("sqlite/lib transpile was generated with SQLITE_OMIT_SEH upstream; full SEH tests live in modernc.org/libsqlite3 pending upstream builder regeneration (make vendor)")
+}

lib/libsqlite3_windows.go

@@ -6,6 +6,8 @@ package sqlite3
 
 import (
 	"math/bits"
+	"runtime/debug"
+	"unsafe"
 
 	"modernc.org/libc"
 )
@@ -14,3 +16,52 @@ func ___umulh(tls *libc.TLS, a, b uint64) uint64 {
 	hi, _ := bits.Mul64(a, b)
 	return hi
 }
+
+func _modernc_seh_try(tls *libc.TLS, pWal uintptr, xTry uintptr, pCtx uintptr, xExcept uintptr) (rc int32) {
+	if pWal == 0 || xTry == 0 {
+		return int32(SQLITE_ERROR)
+	}
+	defer func() {
+		if r := recover(); r != nil {
+			var faultAddr uintptr
+			type addrGetter interface {
+				Addr() uintptr
+			}
+			if ag, ok := r.(addrGetter); ok {
+				faultAddr = ag.Addr()
+			}
+
+			wal := (*TWal)(unsafe.Pointer(pWal))
+			inShm := false
+			if faultAddr != 0 {
+				nPages := int(wal.FnWiData)
+				for i := 0; i < nPages; i++ {
+					pagePtr := *(*uintptr)(unsafe.Pointer(wal.FapWiData + uintptr(i)*unsafe.Sizeof(uintptr(0))))
+					if pagePtr != 0 && faultAddr >= pagePtr && faultAddr < pagePtr+uintptr(32768) {
+						inShm = true
+						break
+					}
+				}
+			} else {
+				inShm = true
+			}
+
+			if inShm {
+				if xExcept != 0 {
+					rc = (*(*func(*libc.TLS, uintptr) int32)(unsafe.Pointer(&struct{ uintptr }{xExcept})))(tls, pWal)
+				} else {
+					rc = int32(SQLITE_IOERR_IN_PAGE)
+				}
+				return
+			}
+
+			panic(r)
+		}
+	}()
+
+	old := debug.SetPanicOnFault(true)
+	defer debug.SetPanicOnFault(old)
+
+	rc = (*(*func(*libc.TLS, uintptr, uintptr) int32)(unsafe.Pointer(&struct{ uintptr }{xTry})))(tls, pWal, pCtx)
+	return rc
+}