What are the valid signatures for C's main() function?

Question

What really are the valid signatures for main function in C? I know:

int main(int argc, char *argv[])

Are there other valid ones?

Answer 1

int main(void)

Under some OS (for example, Windows) also such is valid:

int main(int argc, char **argv, char **envp)

where envp gives an environment, otherwise accessible through getenv()