Disclaimer: my question isn’t practical at all, it’s more a question about 2 codes which allegedly abuse the rules and somewhat compile (with more or less warnings / errors according to the compiler).

As far as I know, the following code is valid C99 :

#include <stdio.h>
#include <stddef.h>

int main(void) {
    size_t n = sizeof(int[printf("%s", "Hello")]);
}

I understand that sizeof doesn’t evaluate an expression unless it is a VLA (because it has non-constant size).

However, I’m not sure if this other piece of code is valid C99 :

#include <stdio.h>

int main(int argc, char** argv);
int main(int argc, char* argv[sizeof(int[printf("%sn", "Hello") + main(0, NULL)])]) {}

• Is it valid to have an array of size sizeof(some VLA) ?
• Is it valid to have a declaration like int main(int, char**) and a definition like int main(int, char*[some size]) ?
• And is it valid to recursively call a function from its own parameters ?

I guess making an array of size sizeof(VLA) is valid, I know no rule which would make this invalid.
If I remember correctly, char*[some size] as function parameter decays to char**, but I don’t know if it’s ill-formed because the declaration/definition don’t perfectly match.
And I have no idea if recursively call main from its parameters is valid or not, I obviously didn’t find any resource or example of a code like this. Also, does main have different rules than other functions about recursive calls in the parameters ?

Quotes from the standard would be very appreciated, thanks a lot.