pull in ncruces/go-sqlite3 v0.20.3 with tetratelabs/wazero v1.8.2 (#3574)

vendor/github.com/ncruces/go-sqlite3/README.md

@@ -77,7 +77,7 @@ It also benefits greatly from [SQLite's](https://sqlite.org/testing.html) and
 Every commit is [tested](https://github.com/ncruces/go-sqlite3/wiki/Test-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)

vendor/github.com/ncruces/go-sqlite3/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 3.47.1 for use with
 [`github.com/ncruces/go-sqlite3`](https://pkg.go.dev/github.com/ncruces/go-sqlite3).
 
 The following optional features are compiled in:

vendor/github.com/ncruces/go-sqlite3/go.work.sum

@@ -9,5 +9,6 @@ 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/tools v0.6.0/go.mod h1:Xwgl3UAJ/d3gWutnCtw505GrjyAbvKui8lOU390QaIU=
 golang.org/x/tools v0.21.1-0.20240508182429-e35e4ccd0d2d/go.mod h1:aiJjzUbINMkxbQROHiO6hDPo2LHcIPhhQsa9DLh0yGk=

vendor/github.com/ncruces/go-sqlite3/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)

vendor/github.com/ncruces/go-sqlite3/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:

vendor/github.com/ncruces/go-sqlite3/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

vendor/github.com/ncruces/go-sqlite3/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
 	}

vendor/github.com/ncruces/go-sqlite3/vfs/os_bsd.go

@@ -15,9 +15,15 @@ func osGetSharedLock(file *os.File) _ErrorCode {
 func osGetReservedLock(file *os.File) _ErrorCode {
 	rc := osLock(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
@@ -33,9 +39,11 @@ 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)
 	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
@@ -50,7 +58,10 @@ 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
 }

vendor/github.com/ncruces/go-sqlite3/vfs/os_dotlk.go

@@ -28,7 +28,8 @@ func osGetSharedLock(file *os.File) _ErrorCode {
 	name := file.Name()
 	locker := vfsDotLocks[name]
 	if locker == nil {
-		err := os.Mkdir(name+".lock", 0777)
+		f, err := os.OpenFile(name+".lock", os.O_RDWR|os.O_CREATE|os.O_EXCL, 0666)
+		f.Close()
 		if errors.Is(err, fs.ErrExist) {
 			return _BUSY // Another process has the lock.
 		}

vendor/github.com/ncruces/go-sqlite3/vfs/os_windows.go

@@ -50,14 +50,17 @@ func osGetExclusiveLock(file *os.File, state *LockLevel) _ErrorCode {
 
 	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)
 	}

vendor/github.com/ncruces/go-sqlite3/vfs/shm_bsd.go

@@ -14,52 +14,52 @@ 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
 	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
 		}
 	}
@@ -67,7 +67,7 @@ func (s *vfsShm) Close() error {
 }
 
 func (s *vfsShm) shmOpen() _ErrorCode {
-	if s.vfsShmFile != nil {
+	if s.vfsShmParent != nil {
 		return _OK
 	}
 
@@ -85,13 +85,13 @@ func (s *vfsShm) shmOpen() _ErrorCode {
 		return _IOERR_FSTAT
 	}
 
-	vfsShmFilesMtx.Lock()
-	defer vfsShmFilesMtx.Unlock()
+	vfsShmListMtx.Lock()
+	defer vfsShmListMtx.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
 		}
@@ -107,18 +107,18 @@ func (s *vfsShm) shmOpen() _ErrorCode {
 	}
 
 	// 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
 }
 
@@ -157,57 +157,11 @@ func (s *vfsShm) shmMap(ctx context.Context, mod api.Module, id, size int32, ext
 func (s *vfsShm) shmLock(offset, n int32, flags _ShmFlag) _ErrorCode {
 	s.Lock()
 	defer s.Unlock()
-
-	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())
-				}
-				if s.vfsShmFile.lock[i] <= 0 {
-					s.vfsShmFile.lock[i] = 0
-				} else {
-					s.vfsShmFile.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.vfsShmFile.lock[i]+1 <= 0 {
-				return _BUSY
-			}
-		}
-		for i := offset; i < offset+n; i++ {
-			s.vfsShmFile.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.vfsShmFile.lock[i] != 0 {
-				return _BUSY
-			}
-		}
-		for i := offset; i < offset+n; i++ {
-			s.vfsShmFile.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.vfsShmFile == nil {
+	if s.vfsShmParent == nil {
 		return
 	}
 

vendor/github.com/ncruces/go-sqlite3/vfs/shm_copy.go

@@ -31,7 +31,10 @@ const (
 //
 // https://sqlite.org/walformat.html#the_wal_index_file_format
 
-func (s *vfsShm) shmAcquire() {
+func (s *vfsShm) shmAcquire(ptr *_ErrorCode) {
+	if ptr != nil && *ptr != _OK {
+		return
+	}
 	if len(s.ptrs) == 0 || shmUnmodified(s.shadow[0][:], s.shared[0][:]) {
 		return
 	}
@@ -69,7 +72,7 @@ func (s *vfsShm) shmRelease() {
 
 func (s *vfsShm) shmBarrier() {
 	s.Lock()
-	s.shmAcquire()
+	s.shmAcquire(nil)
 	s.shmRelease()
 	s.Unlock()
 }

vendor/github.com/ncruces/go-sqlite3/vfs/shm_dotlk.go

@@ -13,22 +13,22 @@ import (
 	"github.com/tetratelabs/wazero/api"
 )
 
-type vfsShmBuffer struct {
+type vfsShmParent struct {
 	shared [][_WALINDEX_PGSZ]byte
-	refs   int // +checklocks:vfsShmBuffersMtx
+	refs   int // +checklocks:vfsShmListMtx
 
 	lock [_SHM_NLOCK]int16 // +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
@@ -40,20 +40,20 @@ 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
 	}
 
@@ -61,22 +61,22 @@ func (s *vfsShm) Close() error {
 	if err != nil && !errors.Is(err, fs.ErrNotExist) {
 		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
 	}
@@ -92,8 +92,8 @@ 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 +112,7 @@ 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 +125,6 @@ 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 +140,26 @@ 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()

vendor/github.com/ncruces/go-sqlite3/vfs/shm_memlk.go

@@ -0,0 +1,55 @@
+//go:build ((freebsd || openbsd || netbsd || dragonfly || illumos) && (386 || arm || amd64 || arm64 || riscv64 || ppc64le) && !sqlite3_nosys) || 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 {
+					panic(util.AssertErr())
+				}
+				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] {
+				panic(util.AssertErr())
+			}
+			if s.vfsShmParent.lock[i]+1 <= 0 {
+				return _BUSY
+			}
+		}
+		for i := offset; i < offset+n; 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] {
+				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
+}

vendor/github.com/ncruces/go-sqlite3/vfs/shm_windows.go

@@ -64,7 +64,7 @@ func (s *vfsShm) shmOpen() _ErrorCode {
 	return osReadLock(s.File, _SHM_DMS, 1, time.Millisecond)
 }
 
-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 +78,7 @@ 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 +107,6 @@ 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 +122,23 @@ 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))