https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103267
--- Comment #4 from Martin Liška <marxin at gcc dot gnu.org> ---
Still, I can't reproduce with the current master.
Apparently, the code snippet from #c0 produces only 2 warnings:
$ gcc pr103267.c -c -O2 && ./a.out
pr103267.c:17:1: warning: return type defaults to ‘int’ [-Wimplicit-int]
17 | test2(int *a)
| ^~~~~
pr103267.c:21:1: warning: return type defaults to ‘int’ [-Wimplicit-int]
21 | main()
| ^~~~
