-Wenum-compare doesn't catch mismatched enum constant comparison in C mode (original) (raw)

Extended Description

Consider this program (test.c)

enum foo_t { foo1, foo2, foo3 };

enum bar_t { bar1, bar2, bar3 };

int main(void) { enum foo_t foo = foo1; enum bar_t bar = bar1;

int cmp1 = foo < bar; // variable - variable
int cmp2 = foo < bar2; // variable - constant
int cmp3 = foo1 < bar3; // constant - constant

return cmp1 || cmp2 || cmp3;

}

If I compile this as C code, I only get a warning for the first comparison. If I compile in C++ mode, I get a warning for all three.

$ clang -Wall test.c test.c:13:20: warning: comparison of two values with different enumeration types ('enum foo_t' and 'enum bar_t') [-Wenum-compare] int cmp1 = foo < bar; ~~~ ^ ~~~ 1 warning generated. $ clang -Wall -x c++ test.c test.c:13:20: warning: comparison of two values with different enumeration types ('enum foo_t' and 'enum bar_t') [-Wenum-compare] int cmp1 = foo < bar; ~~~ ^ ~~~ test.c:14:20: warning: comparison of two values with different enumeration types ('enum foo_t' and 'bar_t') [-Wenum-compare] int cmp2 = foo < bar2; ~~~ ^ ~~~~ test.c:15:21: warning: comparison of two values with different enumeration types ('foo_t' and 'bar_t') [-Wenum-compare] int cmp3 = foo1 < bar3; ~~~~ ^ ~~~~ 3 warnings generated.

I think the warnings should be emitted in C mode too. Tested with gcc 4.9.2 and 3 warnings are emitted for C code:

$ gcc -Wall test.c test.c: In function 'main': test.c:13:20: warning: comparison between 'enum foo_t' and 'enum bar_t' [-Wenum-compare] int cmp1 = foo < bar; ^ test.c:14:20: warning: comparison between 'enum foo_t' and 'enum bar_t' [-Wenum-compare] int cmp2 = foo < bar2; ^ test.c:15:21: warning: comparison between 'enum foo_t' and 'enum bar_t' [-Wenum-compare] int cmp3 = foo1 < bar3; ^