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From: "unlvsur at live dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug libstdc++/115907] Libstdc++ and GCC itself should avoid glibc
 above 2.34 dependency
Date: Sat, 13 Jul 2024 13:08:31 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D115907

--- Comment #12 from cqwrteur <unlvsur at live dot com> ---
(In reply to Andrew Pinski from comment #6)
> There is NO fix inside gcc/libstdc++.
> THe only fix is your build of GCC (which includes the target libraries)
> needs to be build against the oldest version of glibc you support. This is
> something which GCC cannot control.
> THIS IS HOW linking and backwards compatibility works.

Also if you don't think this is a bug. Explain this to me. Why C++ will use
__isoc23_sscanf but C does not?

#include <features.h>
#include <stdio.h>

int main() {
   const char *input =3D "42 Alice";
   int number;

   int result =3D sscanf(input, "%d", &number);

   printf("Parsed number: %d\n", number);

}

g++ -S hello.cc -std=3Dc++11
g++ -S hello.cc -std=3Dc++14
g++ -S hello.cc -std=3Dc++17
g++ -S hello.cc -std=3Dc++20
g++ -S hello.cc -std=3Dc++23

Why they all use __isoc23_sscanf in the latest glibc 2.40.

If we compile it with gcc

gcc -S hello.c -std=3Dc11
gcc -S hello.c -std=3Dc14
gcc -S hello.c -std=3Dc18
gcc -S hello.c -std=3Dc23
Only C23 uses __isoc23_sscanf.

It does not make any sense tbh.=