Inconsistent (missing) incompatible function pointer type warnings #41465
Description
| Bugzilla Link | 42120 |
| Version | trunk |
| OS | All |
| CC | @dwblaikie,@DougGregor,@zygoloid |
Extended Description
Clang marks pointer conversions that add noreturn or noescape information to function types as incompatible (while removing such information is fine), but this warning is not consistent:
$ cat test.cvoid fun00(int *);
void fun01(int *) __attribute__((noreturn));
void fun10(__attribute__((noescape)) int *);
void fun11(__attribute__((noescape)) int *) __attribute__((noreturn));
// OK: safe, no warning
void (*fptr01)(int *) = &fun01;
void (*fptr02)(__attribute__((noescape)) int *) = &fun11;
void (*fptr03)(int *) __attribute__((noreturn)) = &fun11;
// OK: unsafe, warning
void (*fptr11)(int *) __attribute__((noreturn)) = &fun00;
void (*fptr12)(__attribute__((noescape)) int *) = &fun00;
void (*fptr13)(__attribute__((noescape)) int *) __attribute__((noreturn)) = &fun00;
// NOT OK: also unsafe, no warning?
void (*fptr14)(__attribute__((noescape)) int *) = &fun01;
void (*fptr15)(int *) __attribute__((noreturn)) = &fun10;$ clang -c -x c test.c
(only cases fptr11, fptr12, fptr13 are warnings; fptr14 and fptr15 pass without warning/error)Godbolt: https://godbolt.org/z/XjFsFB
That no warnings are issued for fptr14 and fptr15 cases seems wrong. The conversions are at least as dangerous as the fptr11 and fptr12 cases, which do get warnings.
Note that C++ behavior:
$ clang -c -x c++ test.c
(cases fptr11, fptr12, fptr12, fptr13, fptr14, fptr15 are flagged as errors)Godbolt: https://godbolt.org/z/cVjcCQ