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

[Jonathan Wakely]

On 16/01/16 13:41 +0000, Jonathan Wakely wrote:
>On 16/01/16 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.
>>
>>#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
>
>I think it's better to just drop that whole section of the file if TM
>isn't supported, as this patch does.
>
>Bootstraps OK on AIX, still testing on GNU/Linux.

Doh, it causes libitm.c++/libstdc++-safeexc.C to FAIL, because TM
isn't enabled when building libstdc++ ... that's the whole point of
the complicated preprocessor conditions!