[Bug c/53037] warn_if_not_aligned(X)

[hjl.tools at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53037

--- Comment #16 from H.J. Lu <hjl.tools at gmail dot com> 2012-04-19 21:06:49 UTC ---
Created attachment 27199
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=27199
A smaller patch

There is no point to support

struct foo
{
  int i1;
  long long i2  __attribute__((aligned(4), warn_if_not_aligned(8)));
};

since GCC won't decrease alignment in field.  The smaller patch gave

[hjl@gnu-6 pr53037]$ cat x.i
typedef unsigned long long __u64
__attribute__((aligned(4),warn_if_not_aligned(8)));

struct foo1
{
  int i1;
  int i2;
  int i3;
  __u64 x;
};

struct foo2
{
  int i1;
  int i2;
  int i3;
  __u64 x;
} __attribute__((aligned(8)));

struct foo3
{
  int i1;
  int i2;
  __u64 x;
} __attribute__((aligned(8)));

struct foo4
{
  int i1;
  int i3;
  __u64 x;
};

union bar1
{
  int i1;
  int i3;
  __u64 x;
};

union bar2
{
  int i1;
  int i3;
  __u64 x;
} __attribute__((aligned(8)));
[hjl@gnu-6 pr53037]$ make x.s
/export/build/gnu/gcc/build-x86_64-linux/gcc/xgcc
-B/export/build/gnu/gcc/build-x86_64-linux/gcc/ -mx32 -Wall -O2 -S x.i
x.i:10:1: warning: alignment 4 of ‘struct foo1’ is less than 8 [enabled by
default]
 };
 ^
x.i:9:9: warning: ‘x’ offset 12 in ‘struct foo1’ isn't aligned to 8 [enabled by
default]
   __u64 x;
         ^
x.i:17:9: warning: ‘x’ offset 12 in ‘struct foo2’ isn't aligned to 8 [enabled
by default]
   __u64 x;
         ^
x.i:32:1: warning: alignment 4 of ‘struct foo4’ is less than 8 [enabled by
default]
 };
 ^
x.i:39:1: warning: alignment 4 of ‘union bar1’ is less than 8 [enabled by
default]
 };
 ^
[hjl@gnu-6 pr53037]$