cmd/link: flush file mapping before unmapping

Call FlushViewOfFile before unmapping the output file, for extra safety. The documentation says the function does not wait for the data to be written to disk, so it should be cheap. Fixes golang#38440. Change-Id: I05352f15d9305e6e7086a002f61802f74036b710 Reviewed-on: https://go-review.googlesource.com/c/go/+/235639 Reviewed-by: Austin Clements <[email protected]> Reviewed-by: Jason A. Donenfeld <[email protected]>
EzioZz · Jun 1, 2020 · 13bc6d4 · 13bc6d4
1 parent 8be0de1
commit 13bc6d4
Showing 1 changed file with 7 additions and 1 deletion.
diff --git a/src/cmd/link/internal/ld/outbuf_windows.go b/src/cmd/link/internal/ld/outbuf_windows.go
@@ -35,7 +35,13 @@ func (out *OutBuf) munmap() {
 	if out.buf == nil {
 		return
 	}
-	err := syscall.UnmapViewOfFile(uintptr(unsafe.Pointer(&out.buf[0])))
+	// Apparently unmapping without flush may cause ACCESS_DENIED error
+	// (see issue 38440).
+	err := syscall.FlushViewOfFile(uintptr(unsafe.Pointer(&out.buf[0])), 0)
+	if err != nil {
+		Exitf("FlushViewOfFile failed: %v", err)
+	}
+	err = syscall.UnmapViewOfFile(uintptr(unsafe.Pointer(&out.buf[0])))
 	out.buf = nil
 	if err != nil {
 		Exitf("UnmapViewOfFile failed: %v", err)