MaskRay added a comment.
In D148827#4422709 <https://reviews.llvm.org/D148827#4422709>, @glandium wrote:
> OTOH. 6.2.7.3:
>
>> A composite type can be constructed from two types that are compatible; it
>> is a type that is compatible with both of the two types (...)
>
> 6.2.7.5:
>
>> EXAMPLE Given the following two file scope declarations:
>> int f(int (*)(), double (*)[3]);
>> int f(int (*)(char *), double (*)[]);
>> The resulting composite type for the function is:
>> int f(int (*)(char *), double (*)[3]);
>
> This suggests that `int(*)()` and `int(*)(char*)` are compatible.
Yes, I mentioned this in my previous comment. This fragment is overly strict
but I think it should be fine in practice. This mismatching is uncommon and
old-style (parameter-less) definitions will be unsupported in C2x anyway.
The other direction is worked around by this patch (see
`!isa<FunctionNoProtoType>(PointeeType)`).
int foo() { return 42; } // old-style (parameter-less) definition, warned by
-Wstrict-prototypes unless -std=c2x
int main(void) {
//int (*qux)(int) = (int (*)(int))foo;
//qux(42); // rejected by -fsanitize=function
...
> 6.2.7.2:
>
>> All declarations that refer to the same object or function shall have
>> compatible type; otherwise, the behavior is undefined.
>
> 6.3.2.3.1:
>
>> A pointer to void may be converted to or from a pointer to any object type.
>> A pointer to any object type may be converted to a pointer to void and back
>> again; the result shall compare equal to the original pointer.
>
> These are either contradicting, making 6.3.2.3.1 UB, or void* is compatible
> with other pointer types.
6.3.2.3.1 is about a pointer casting rule, which is different from type
compatibility.
In C++, there is no C type compatibility rule, but we can still cast pointers.
To elaborate my previous comment about working around C projects, you can use
the following to suppress instrumentation for all `.c` files (but not `.cc` or
`.cpp`)
# -fsanitize=undefined -fsanitize-ignorelist=a.ignorelist
% cat a.ignorelist
[function]
src:*\.c
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D148827/new/
https://reviews.llvm.org/D148827
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