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 6aad39348323b293bdc18505787066fc693ee897..dcce4cbe4786c25a5a05e63bdca91ed037b043ce 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -576,6 +576,7 @@ ifeq ($(shell $(CONFIG_SHELL) $(srctree)/scripts/gcc-stack-usage.sh $(CC)),y)
 endif
 
 KBUILD_CFLAGS += $(call cc-option,-Wno-format-nonliteral)
+KBUILD_CFLAGS += $(call cc-disable-warning, address-of-packed-member)
 
 # turn jbsr into jsr for m68k
 ifeq ($(ARCH),m68k)