https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103334
Bug ID: 103334
Summary: missing -Wc++-compat for a function redeclared with
different qualifiers
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: msebor at gcc dot gnu.org
Target Milestone: ---
Redeclaring a function that differs only in the qualifiers on the return type
is rejected by G++ in all C++ modes but not diagnosed by GCC in C mode. The
warbing should be enhanced to diagnose that as well (-Wignored-qualifiers is
enabled by -Wextra but not -Wall).
$ cat z.c && gcc -O2 -S -Wall -Wextra -Wc++-compat z.c
const int f (void);
volatile int f (void);
z.c:1:1: warning: type qualifiers ignored on function return type
[-Wignored-qualifiers]
1 | const int f (void);
| ^~~~~
z.c:2:1: warning: type qualifiers ignored on function return type
[-Wignored-qualifiers]
2 | volatile int f (void);
| ^~~~~~~~
Compilation error for the same code with G++:
$ g++ -O2 -S -Wall -Wextra -std=c++98 -xc++ z.c
z.c:1:1: warning: type qualifiers ignored on function return type
[-Wignored-qualifiers]
1 | const int f (void);
| ^~~~~
z.c:2:1: warning: type qualifiers ignored on function return type
[-Wignored-qualifiers]
2 | volatile int f (void);
| ^~~~~~~~
z.c:2:14: error: ambiguating new declaration of ‘volatile int f()’
2 | volatile int f (void);
| ^
z.c:1:11: note: old declaration ‘const int f()’
1 | const int f (void);
| ^
