On Sat, 2018-12-01 at 22:14 +0100, Kamil Rytarowski wrote:
> We define a fallback version of __func__ for pre-C99 compilers in
> <sys/cdefs.h>
>
> 416 /*
> 417 * C99 defines __func__ predefined identifier, which was made available
> 418 * in GCC 2.95.
> 419 */
> 420 #if !(__STDC_VERSION__ >= 199901L)
> 421 #if __GNUC_PREREQ__(2, 6)
> 422 #define __func__ __PRETTY_FUNCTION__
> 423 #elif __GNUC_PREREQ__(2, 4)
> 424 #define __func__ __FUNCTION__
> 425 #else
> 426 #define __func__ ""
> 427 #endif
> 428 #endif /* !(__STDC_VERSION__ >= 199901L) */
>
> -- https://nxr.netbsd.org/xref/src/sys/sys/cdefs.h#416
>
> __func__ has been imported into C++11 along with the C99 compatibility
> support and I believe that by accident we redefine it for all C++ programs.
>
> According to C++ papers, __func__ is an implementation-defined string.
>
> -- http://eel.is/c++draft/dcl.dcl#dcl.fct.def.general-8
>
> However the current version causes a mismatch between NetBSD and the world:
>
> $ cat test.cc
> #include <stdio.h>
> int
> main(int argc, char **argv)
> {
> printf("%s\n", __func__);
> return 0;
> }
> $ ./a.out
> int main(int, char **)
>
> vs others:
>
> $ cat test.cc
> #include <stdio.h>
> int
> main(int argc, char **argv)
> {
> printf("%s\n", __func__);
> return 0;
> }
> $ ./a.out
> main
>
> The same behavior is presented in G++ and Clang++.
>
> While both versions are compliant with C++11, this causes unnecessary
> difference in regression tests, in particular in the LLVM project.
>
> I wrote a patch to stop redefining __func__ for C++11, analogous to the
> existing logic for C99.
>
> http://netbsd.org/~kamil/patch-00076-__func__-cpp11.txt
>
> I've found that a similar issue was also detected at least in fish shell
> and developers mentioned the NetBSD case in the thread.
>
> https://github.com/fish-shell/fish-shell/commit/574851f092358f5834afb0b529676924fcbd59c6
>
> I've discussed this with Michal, who has detected the issue in the LLVM
> regression tests (https://reviews.llvm.org/D55162) and he has a
> different opinion on __func__ and C++. I will let him explain it here.
Actually, I misread your patch and now that I read it the second time,
I agree with it. Sorry for the trouble ;-).
--
Best regards,
Michał Górny
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