https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97321
Bug ID: 97321 Summary: add warning for pointer casts that may lead to aliasing violation when dereferenced Product: gcc Version: 10.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c Assignee: unassigned at gcc dot gnu.org Reporter: nsz at gcc dot gnu.org Target Milestone: --- consider: int f(unsigned char **); int g(char *p) { return f((unsigned char **)&p); } such code is almost surely wrong (if f dereferences its argument) this is a common mistake and it seems gcc-11 will optimize such code more aggressively which can lead to broken behavior, see bug 97264. so it would be useful to simply warn about casts between pointer types that cannot alias. e.g.: "warning: dangerous cast from `char **` to `unsigned char **` can lead to aliasing violation [-Wpointer-cast]" does not have to be in -Wall, but the current aliasing warnings are too weak to catch bugs like in the example.