gcc-9: silence 'address-of-packed-member' warning

GCC 9.x starts complaining about potential misalignment of the pointer to
the array (in this case alignment=2) in the packed (alignment=1) structures.

Repeating Linus' Torvalds commit 6f303d60534c in the Linux kernel.

Original commit message:

  We already did this for clang, but now gcc has that warning too.
  Yes, yes, the address may be unaligned.  And that's kind of the point.

This in particular hides the warnings like

drivers/usb/gadget/composite.c:545:23: warning: taking address of packed member of ‘struct usb_string_descriptor’ may result in an unaligned pointer value [-Waddress-of-packed-member]
  545 |    collect_langs(sp, s->wData);

drivers/usb/gadget/composite.c:550:24: warning: taking address of packed member of ‘struct usb_string_descriptor’ may result in an unaligned pointer value [-Waddress-of-packed-member]
  550 |     collect_langs(sp, s->wData);

drivers/usb/gadget/composite.c:555:25: warning: taking address of packed member of ‘struct usb_string_descriptor’ may result in an unaligned pointer value [-Waddress-of-packed-member]
  555 |      collect_langs(sp, s->wData);

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

diff --git a/Makefile b/Makefile
index cc126ebc53b5918a4618eeb03d50c9724bf6fd3b..3f332e68856d132db60c5b9fca8c62fa371fab82 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -672,11 +672,12 @@ endif
 endif
 
 KBUILD_CFLAGS += $(call cc-option,-Wno-format-nonliteral)
+KBUILD_CFLAGS += $(call cc-disable-warning, address-of-packed-member)
+
 ifeq ($(cc-name),clang)
 KBUILD_CPPFLAGS += $(call cc-option,-Qunused-arguments,)
 KBUILD_CFLAGS += $(call cc-disable-warning, format-invalid-specifier)
 KBUILD_CFLAGS += $(call cc-disable-warning, gnu)
-KBUILD_CFLAGS += $(call cc-disable-warning, address-of-packed-member)
 KBUILD_CFLAGS += $(call cc-option, -fcatch-undefined-behavior)
 endif