[committed] Fix -Wmissing-attributes warning in libstdc++ (PR libstdc++/89402)

[Jonathan Wakely]

On 22/02/19 02:23 +0100, Jakub Jelinek wrote:
>On Fri, Feb 22, 2019 at 01:10:32AM +0000, Jonathan Wakely wrote:
>> On 20/02/19 09:07 +0100, Jakub Jelinek wrote:
>> > Hi!
>> >
>> > The following patch fixes a warning when building on targets where long
>> > double switched from being the same as double to something wider,
>> > like e.g. powerpc*-linux, alpha*-linux, s390*-linux etc.
>> >
>> > Fixed thusly, bootstrapped/regtested on {x86_64,i686,s390x}-linux and
>> > bootstrapped on powerpc64le-linux, on both s390x and powerpc64le it removed
>> > all
>> > ../../../../libstdc++-v3/src/c++98/compatibility-ldbl.cc:77:17: warning: 'void _ZNKSt4hashIeEclEe()' specifies less restrictive attribute than its target 'std::size_t std::tr1::hash<_Tp>::operator()(_Tp) const [with _Tp = long double]': 'pure' [-Wmissing-attributes]
>> > warnings from the build log.  Preapproved by Jonathan in the PR, committed
>> > to trunk.
>>
>> Now I see:
>>
>> /home/jwakely/src/gcc/libstdc++-v3/src/c++98/compatibility-ldbl.cc:78:65: warning: ‘pure’ attribute on function returning ‘void’ [-Wattributes]
>>   78 |   _GLIBCXX_PURE __attribute__((alias ("_ZNKSt3tr14hashIeEclEe")));
>>      |                                                                 ^
>>
>> We can disable that with a diagnostic pragma.
>
>Oops, sorry, missed that.
>Or make it extern "C" size_t _ZNKSt4hashIeEclEe (long double) or so, after all,
>that is what it returns and what it takes as an argument.

Ah yes, even better.

>> > 2019-02-20  Jakub Jelinek  <jakub@redhat.com>
>> >
>> > 	PR libstdc++/89402
>> > 	* src/c++98/compatibility-ldbl.cc (_ZNKSt4hashIeEclEe): Add
>> > 	_GLIBCXX_PURE to the alias declaration.
>> >
>> > --- libstdc++-v3/src/c++98/compatibility-ldbl.cc.jj	2019-01-01 12:39:41.530606161 +0100
>> > +++ libstdc++-v3/src/c++98/compatibility-ldbl.cc	2019-02-19 16:12:52.402123217 +0100
>> > @@ -75,6 +75,6 @@ namespace std _GLIBCXX_VISIBILITY(defaul
>> > // and std::hash<long double>::operator()
>> > // are the same, no need to duplicate them.
>> > extern "C" void _ZNKSt4hashIeEclEe (void)
>> > -  __attribute__((alias ("_ZNKSt3tr14hashIeEclEe")));
>> > +  _GLIBCXX_PURE __attribute__((alias ("_ZNKSt3tr14hashIeEclEe")));
>> >
>> > #endif
>
>	Jakub