Re: [PATCH 13/13] fix incompatible posix_memalign declaration on x86

[Szabolcs Nagy <szabolcs dot nagy at arm dot com>]

On 15/05/15 16:05, H.J. Lu wrote:
> On Mon, Apr 20, 2015 at 12:00 PM, Szabolcs Nagy <szabolcs.nagy@arm.com> wrote:
>> The posix_memalign declaration is incompatible with musl for C++,
>> because of the exception specification.  It also pollutes the
>> namespace and lacks protection against a potential macro definition
>> that is allowed by POSIX.  The fix avoids source level namespace
>> pollution but retains the dependency on the posix_memalign extern
>> libc symbol.
>>
>> The fix is ugly, but it is not possible to correctly redeclare a
>> libc function in a public gcc header for C++.
>>
>>
>> gcc/Changelog:
>>
>> 2015-04-16  Szabolcs Nagy  <szabolcs.nagy@arm.com>
>>
>>         * config/i386/pmm_malloc.h (posix_memalign): Renamed to ...
>>         (__gcc_posix_memalign): This.  Use posix_memalign as extern
>>         symbol only.
> 
> What does this try to achieve?  Do you have a testcase which
> fails before and passes with this patch?

if posix_memalign is defined in stdlib.h according to posix then
the exception specifier used in mm_malloc.h is incompatible:

$ echo "#include <mm_malloc.h>" | ./x86_64-linux-musl-g++ -pedantic -c -xc++ -D_POSIX_C_SOURCE=200809L -
In file included from <stdin>:1:0:
/data/cross/x86_64-linux-musl/lib/gcc/x86_64-linux-musl/6.0.0/include/mm_malloc.h:34:64: error: declaration of 'int posix_memalign(void**, size_t,
size_t) throw ()' has a different exception specifier
 extern "C" int posix_memalign (void **, size_t, size_t) throw ()
                                                                ^
In file included from /data/cross/x86_64-linux-musl/lib/gcc/x86_64-linux-musl/6.0.0/include/mm_malloc.h:27:0,
                 from <stdin>:1:
/data/cross/x86_64-linux-musl/x86_64-linux-musl/include/stdlib.h:98:5: error: from previous declaration 'int posix_memalign(void**, size_t, size_t)'
 int posix_memalign (void **, size_t, size_t);
     ^

however it seems without -pedantic there is no error anymore,
the code is accepted even in standard conforming mode.
(it used to be an error that could not be silenced).

this means the patch is no longer critical for musl support.