https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84055
Martin Sebor <msebor at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Last reconfirmed| |2018-01-26
CC| |msebor at gcc dot gnu.org
Ever confirmed|0 |1
Known to fail| |7.2.0, 8.0
--- Comment #3 from Martin Sebor <msebor at gcc dot gnu.org> ---
I think it's just a matter of G++ warning that a type attribute is being
dropped when instantiating a template on the type. This is not entirely
intuitive and there have been other bug reports in the past as a result.
Here's a small test case:
$ cat t.C && gcc -S -Wall t.C
typedef unsigned cl_uint __attribute__((aligned(4)));
template <class T>
struct vector { };
vector<cl_uint> v;
t.C:6:15: warning: ignoring attributes on template argument ‘cl_uint’ {aka
‘unsigned int’} [-Wignored-attributes]
vector<cl_uint> v;
^
I'll go ahead and confirm this report because the attribute here is superfluous
when an int is 4-byte aligned and so GCC might as well just silently drop it
when it's explicitly specified and avoid issuing a pointless warning.
I also confirm it because I'm bothered by the warning being issued
inconsistently. For example, in the test case below, instantiating the class
template A on I4 triggers the (pointless in this case) -Wignored-attributes
warning but instantiating the function template g on f does not even though the
-Wreturn-type warning implies that the noreturn attribute was dropped. I think
GCC should be consistent, if not in applying/dropping attributes then in
issuing the -Wignored-attributes warning.
$ cat t.C && gcc -S -Wall t.C
typedef int I4 __attribute__ ((aligned (4)));
template <class T>
struct A { };
template struct A<I4>;
int __attribute__ ((noreturn)) f ();
template <class T>
int g (T t) { t (); }
void h ()
{
g (f);
}
t.C:5:21: warning: ignoring attributes on template argument ‘I4’ {aka ‘int’}
[-Wignored-attributes]
template struct A<I4>;
^
t.C: In function ‘int g(T)’:
t.C:10:21: warning: no return statement in function returning non-void
[-Wreturn-type]
int g (T t) { t (); }
^
