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typeof_unqual behaves differently in gcc and clang
C23 6.7.3.6 contains this (informative) example demonstrating the use of typeof_unqual:
const char* const animals[] = {
"aardvark",
"bluejay",
"catte",
};
typeof_unqual(animals) animals2_array[3];
And this is supposedly equivalent to const char* animals2_array[3]; according to the example. That is also the result I get from clang 19.1.
But in gcc 14.2 I get the type const char* const [3].
Full example: https://godbolt.org/z/Gf9M43nrM
What is correct? Is the standard unclear? The parts about typeof_unqual in 6.7.3.6 do not mention arrays at all.
1 answer
The C23 example as well as clang are correct. This is apparently a gcc bug in the latest 14.2 release, fixed in the "gcc (trunk)" unreleased version.
The relevant part of the C23 standard here is 6.7.4.1 §10:
If the specification of an array type includes any type qualifiers, both the array and the element type are so-qualified.
(Also mentioned in 6.2.5 §31)
In this case the element type is const char* const, where the first const belongs to the pointed-at type and the second const qualifies the pointer itself. Therefore because of the second const, the array item is const qualified. And therefore, according to the quoted part above, the whole array is const qualified too.
Meaning that typeof_unqual should remove the const from the array type but not from the pointed-at item. This gives us a const char* [3].
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