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
