Re: [PATCH v2] libstdc++: Make certain exceptions transaction_safe.

[David Edelsohn <dje dot gcc at gmail dot com>]

Torvald,

The error is a link failure in stage2 configure due to the missing
_ITM_xxx and related symbols.  I don't have the failed build any more.
Maybe Jonathan can reply with the specific failures.

There is an AIX system in the GNU Compile Farm: gcc111.

- David

On Sat, Jan 16, 2016 at 3:12 PM, Torvald Riegel <triegel@redhat.com> wrote:
> On Sat, 2016-01-16 at 14:35 +0100, Jakub Jelinek wrote:
>> On Sat, Jan 16, 2016 at 07:47:33AM -0500, David Edelsohn wrote:
>> > stage1 libstdc++ builds just fine.  the problem is stage2 configure
>> > fails due to missing ITM_xxx symbols when configure tries to compile
>> > and run conftest programs.
>>
>> On x86_64-linux, the _ITM_xxx symbols are undef weak ones and thus it is
>> fine to load libstdc++ without libitm and libstdc++ doesn't depend on
>> libitm.
>>
>> So, is AIX defining __GXX_WEAK__ or not?  Perhaps some other macro or
>> configure check needs to be used to determine if undefined weak symbols
>> work the way libstdc++ needs them to.
>
> David, if you can tell me what AIX supports and whether it defines
> __GXX_WEAK__ with the semantics we assume here, I can see what a fix
> would be.  As Jakub says, the point of all what's below is to actually
> make it work when there's no TM support.
>
> Also, knowing the actual error that AIX fails with would be helpful.  I
> have no access to AIX, so can't check.  Thanks.
>
>> #if __GXX_WEAK__
>> // Declare all libitm symbols we rely on, but make them weak so that we do
>> // not depend on libitm.
>> extern void* _ZGTtnaX (size_t sz) __attribute__((weak));
>> extern void _ZGTtdlPv (void* ptr) __attribute__((weak));
>> extern uint8_t _ITM_RU1(const uint8_t *p)
>>   ITM_REGPARM __attribute__((weak));
>> extern uint32_t _ITM_RU4(const uint32_t *p)
>>   ITM_REGPARM __attribute__((weak));
>> extern uint64_t _ITM_RU8(const uint64_t *p)
>>   ITM_REGPARM __attribute__((weak));
>> extern void _ITM_memcpyRtWn(void *, const void *, size_t)
>>   ITM_REGPARM __attribute__((weak));
>> extern void _ITM_memcpyRnWt(void *, const void *, size_t)
>>   ITM_REGPARM __attribute__((weak));
>> extern void _ITM_addUserCommitAction(void (*)(void *), uint64_t, void *)
>>   ITM_REGPARM __attribute__((weak));
>>
>> #else
>> // If there is no support for weak symbols, create dummies.  The exceptions
>> // will not be declared transaction_safe in this case.
>> void* _ZGTtnaX (size_t) { return NULL; }
>> void _ZGTtdlPv (void*) { }
>> uint8_t _ITM_RU1(const uint8_t *) { return 0; }
>> uint32_t _ITM_RU4(const uint32_t *) { return 0; }
>> uint64_t _ITM_RU8(const uint64_t *) { return 0; }
>> void _ITM_memcpyRtWn(void *, const void *, size_t) { }
>> void _ITM_memcpyRnWt(void *, const void *, size_t) { }
>> void _ITM_addUserCommitAction(void (*)(void *), uint64_t, void *) { };
>> #endif
>>
>>       Jakub
>
>
>