[release-branch.go1.10] cmd/cgo: disable GCC 9 warnings triggered by cgo code

GCC 9 has started emitting warnings when taking the address of a field
in a packed struct may cause a misaligned pointer. We use packed
structs in cgo to ensure that our field layout matches the C
compiler's layout. Our pointers are always aligned, so disable the warning

Updates #29962
Fixes #29966

Change-Id: I7e290a7cf694a2c2958529e340ebed9fcd62089c
Reviewed-on: https://go-review.googlesource.com/c/159859
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>
(cherry picked from commit f2a416b90ac68596ea05b97cefa8c72e7416e98f)
Reviewed-on: https://go-review.googlesource.com/c/160450
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
This commit is contained in:
Ian Lance Taylor 2019-01-28 12:31:55 -08:00 committed by Brad Fitzpatrick
parent d4cf10b9d6
commit 396ff0df0a

View File

@ -743,6 +743,10 @@ func (p *Package) writeExports(fgo2, fm, fgcc, fgcch io.Writer) {
fmt.Fprintf(fgcc, "#include <stdlib.h>\n") fmt.Fprintf(fgcc, "#include <stdlib.h>\n")
fmt.Fprintf(fgcc, "#include \"_cgo_export.h\"\n\n") fmt.Fprintf(fgcc, "#include \"_cgo_export.h\"\n\n")
// We use packed structs, but they are always aligned.
fmt.Fprintf(fgcc, "#pragma GCC diagnostic ignored \"-Wpragmas\"\n")
fmt.Fprintf(fgcc, "#pragma GCC diagnostic ignored \"-Waddress-of-packed-member\"\n")
fmt.Fprintf(fgcc, "extern void crosscall2(void (*fn)(void *, int, __SIZE_TYPE__), void *, int, __SIZE_TYPE__);\n") fmt.Fprintf(fgcc, "extern void crosscall2(void (*fn)(void *, int, __SIZE_TYPE__), void *, int, __SIZE_TYPE__);\n")
fmt.Fprintf(fgcc, "extern __SIZE_TYPE__ _cgo_wait_runtime_init_done();\n") fmt.Fprintf(fgcc, "extern __SIZE_TYPE__ _cgo_wait_runtime_init_done();\n")
fmt.Fprintf(fgcc, "extern void _cgo_release_context(__SIZE_TYPE__);\n\n") fmt.Fprintf(fgcc, "extern void _cgo_release_context(__SIZE_TYPE__);\n\n")
@ -1334,6 +1338,10 @@ __cgo_size_assert(double, 8)
extern char* _cgo_topofstack(void); extern char* _cgo_topofstack(void);
/* We use packed structs, but they are always aligned. */
#pragma GCC diagnostic ignored "-Wpragmas"
#pragma GCC diagnostic ignored "-Waddress-of-packed-member"
#include <errno.h> #include <errno.h>
#include <string.h> #include <string.h>
` `