https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95277
Bug ID: 95277
Summary: error on alignment for a function argument
Product: gcc
Version: 10.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: middle-end
Assignee: unassigned at gcc dot gnu.org
Reporter: msebor at gcc dot gnu.org
Target Milestone: ---
Declaring a local variable with attribute aligned is accepted. Declaring a
function argument with an overligned type is also accepted.
However, specifying attribute aligned on a function argument is rejected. The
error doesn't say why the attribute may not be specified, and the manual
doesn't say that specifying the attribute on function arguments is not allowed.
The same code is accepted by Clang.
Either the code should be accepted with the same effect as in Clang, or the
manual (and ideally also the error) should be updated to explain why the
attribute may not be specified this way.
$ cat z.c && gcc -S -Wall -Wextra z.c
void f (void)
{
__attribute__ ((aligned (256))) char c; // accepted
_Static_assert (__alignof__ (c) == 256, "#1"); // passes
}
typedef __attribute__ ((aligned (256))) char C256;
void g (C256 c) // accepted
{
_Static_assert (__alignof__ (c) == 256, "#2"); // passes
}
void h (__attribute__ ((aligned (256))) char c) // error
{
_Static_assert (__alignof__ (c) == 256, "#3");
}
z.c:14:46: error: alignment may not be specified for ‘c’
14 | void h (__attribute__ ((aligned (256))) char c) // error
| ~~~~~^
z.c: In function ‘h’:
z.c:16:3: error: static assertion failed: "#3"
16 | _Static_assert (__alignof__ (c) == 256, "#3");
| ^~~~~~~~~~~~~~
