On Thu, Jan 12, 2017 at 05:53:06PM +0000, Joseph Myers wrote:
> On Thu, 15 Dec 2016, Aaron Sawdey wrote:
>
> > + emit_library_call_value (gen_rtx_SYMBOL_REF (Pmode, "strncmp"),
> > + target, LCT_NORMAL, GET_MODE (target), 3,
> > + force_reg (Pmode, XEXP (src1, 0)), Pmode,
> > + force_reg (Pmode, XEXP (src2, 0)), Pmode,
> > + len_rtx, GET_MODE (len_rtx));
>
> Building glibc with GCC mainline for powerpc64le-linux-gnu (from my bot
> doing such builds and compilation parts of the testsuite for all GNU/Linux
> glibc ABIs daily), I'm seeing a failure of the elf/check-localplt test,
> "Extra PLT reference: libc.so: strncmp".
>
> Without having bisected, I suspect this patch of being a likely cause of
> that failure. glibc redirects internal calls to use hidden aliases such
> as __GI_strncmp to avoid them going through the PLT. By using
> gen_rtx_SYMBOL_REF there with a hardcoded function name "strncmp", this
> code looks like it would render a declaration of strncmp with asm
> ("__GI_strncmp") ineffective, generating a direct call to strncmp when
> glibc expects __GI_strncmp to be called instead.
>
> I don't know how readily this code can be made to respect asm renaming of
> strncmp. If it's hard to fix in GCC, I suppose glibc needs a powerpc
> version of symbol-hacks.h to handle this redirection.
Tulio will look at fixing it in glibc tomorrow. Thanks for the report,
Segher
