Fix crashes.

internal/util/mmap.go

@@ -73,11 +73,7 @@ func MapRegion(ctx context.Context, mod api.Module, f *os.File, offset int64, si
 }
 
 func (r *MappedRegion) Close() error {
-	if addr := r.addr; addr != 0 {
-		r.addr = 0
-		return munmap(addr, uintptr(r.size))
-	}
-	return nil
+	return munmap(r.addr, uintptr(r.size))
 }
 
 func (r *MappedRegion) Unmap() error {

tests/wal_test.go

@@ -1,12 +1,24 @@
 package tests
 
 import (
+	"os"
 	"path/filepath"
 	"testing"
 
 	"github.com/ncruces/go-sqlite3"
+	"github.com/ncruces/go-sqlite3/vfs"
+	"github.com/tetratelabs/wazero"
 )
 
+func TestMain(m *testing.M) {
+	if vfs.SupportsSharedMemory {
+		sqlite3.RuntimeConfig = wazero.NewRuntimeConfig().
+			WithMemoryCapacityFromMax(true).
+			WithMemoryLimitPages(1024)
+	}
+	os.Exit(m.Run())
+}
+
 func TestWAL_enter_exit(t *testing.T) {
 	t.Parallel()
 

vfs/shm.go

@@ -6,7 +6,7 @@ import (
 	"context"
 	"io"
 	"os"
-	"unsafe"
+	"reflect"
 
 	"github.com/ncruces/go-sqlite3/internal/util"
 	"github.com/tetratelabs/wazero/api"
@@ -24,20 +24,16 @@ import (
 const SupportsSharedMemory = true
 
 func vfsVersion(mod api.Module) uint32 {
-	pagesize := unix.Getpagesize()
-
 	// 32KB pages must be a multiple of the system's page size.
-	if (32*1024)%pagesize != 0 {
+	if (32*1024)%unix.Getpagesize() != 0 {
 		return 0
 	}
 
-	// The module's memory must be page aligned.
-	b, ok := mod.Memory().Read(0, 1)
-	if ok && uintptr(unsafe.Pointer(&b[0]))%uintptr(pagesize) != 0 {
+	// Memory must have been mmaped.
+	if reflect.ValueOf(mod.Memory()).Elem().FieldByName("mmappedBuffer").IsNil() {
 		return 0
 	}
-
-	return 1 // TODO: feeling lucky?
+	return 1
 }
 
 type vfsShm struct {