On Fri, 12 May 2023, Gabriel Ravier via Gcc wrote:
> On 5/12/23 19:52, Florian Weimer wrote: > > I think we have another problem. > > > > We do not warn by default for: > > > > int x; > > unsigned *p; > > > > p = &x; > > > > Isn't that a conformance issue because the pointers are incompatible, > > requiring a diagnostic? > > > > Furthermore, Unlike the char case, this tends to introduce > > strict-aliasing violations, so there is a good reason to treat this > > variant as an error (even if we would only warn for char * and > > unsigned char *). > > Isn't this allowed by the standard ? 6.5.7. Expressions states: > > An object shall have its stored value accessed only by an lvalue > expression that has one of thefollowing types:[...] - a type that is the > signed or unsigned type corresponding to the effective type of the object The standard allows aliasing, but not assigning pointers without a cast. This is valid: unsigned x; int *p = (void *)&x; *p = 0; This is not valid (constraint violation): unsigned x; int *p = &x; In GCC this is diagnosed under -Wpointer-sign: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=25892 Alexander
