[Bug c/78359] Redeclaration of global variables is not reported

[egall at gwmail dot gwu.edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78359

Eric Gallager <egall at gwmail dot gwu.edu> changed:

           What    |Removed                     |Added
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                 CC|                            |egall at gwmail dot gwu.edu

--- Comment #6 from Eric Gallager <egall at gwmail dot gwu.edu> ---
(In reply to Andrew Pinski from comment #4)
> (In reply to hugo74 from comment #2)
> > It should not work that way. I checked it in other C compilers and each of
> > them reports an redefinition error in such case.
> 
> Are you sure they were C compilers and not C++ compilers?
> 
> C and C++ differ here.

Hence -Wc++-compat gets the warning desired:

$ /usr/local/bin/gcc -Wall -Wextra -pedantic -Wredundant-decls -Wc++-compat
-fno-common -c pr78359.c
pr78359.c:1:14: warning: duplicate declaration of ‘Counter’ is invalid in C++
[-Wc++-compat]
 int Counter, Counter, Counter;
              ^~~~~~~
pr78359.c:1:5: note: previous declaration of ‘Counter’ was here
 int Counter, Counter, Counter;
     ^~~~~~~
pr78359.c:1:23: warning: duplicate declaration of ‘Counter’ is invalid in C++
[-Wc++-compat]
 int Counter, Counter, Counter;
                       ^~~~~~~
pr78359.c:1:14: note: previous declaration of ‘Counter’ was here
 int Counter, Counter, Counter;
              ^~~~~~~