Le paramètre env n'est pas standard.

5.1.2.2.1 Program startup
1 The function called at program startup is named main. The implementation declares no prototype for this function. It shall be defined with a return type of int and with no parameters:
int main(void) { /* ... */ }
or with two parameters (referred to here as argc and argv, though any names may be used, as they are local to the function in which they are declared):
int main(int argc, char *argv[]) { /* ... */ }
or equivalent;⁹⁾ or in some other implementation-defined manner.

9) Thus, int can be replaced by a typedef name defined as int, or the type of argv can be written as char ** argv, and so on.

(WG14/N1256 ISO/IEC 9899:TC3)