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

POSIX supports execve(), which in turn supports

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

The added argument is the environment, i.e. an array of strings of the form NAME=VALUE.