https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63495
Bug ID: 63495
Summary: struct __attribute__ ((aligned (8))) broken on x86
Product: gcc
Version: 4.9.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: eggert at gnu dot org
Compile and run the following two-line program with an x86 target:
struct __attribute__ ((aligned (8))) s { char c; };
_Static_assert (_Alignof (struct s) >= 8, "wrong alignment");
This should compile, but here are the symptoms I observe with GCC 4.9.1:
$ gcc -m32 t.c
t.c:2:1: error: static assertion failed: "wrong alignment"
_Static_assert (_Alignof (struct s) >= 8, "wrong alignment");
^
On the buggy platform the structure's alignment is 4; it should be 8.
The program compiles fine with GCC 4.8.3, so there is a regression here. The
program also compiles fine on x86-64.
The alignment bug breaks the trunk version of GNU Emacs when built on a 32-bit
platform; see
<http://lists.gnu.org/archive/html/emacs-devel/2014-10/msg00261.html>. I'll
try to fix Emacs to work around the bug, but the GCC bug really should get
fixed.
