Throw warnings when using zero modulus in gmp_powm

Also fixes a leak in this case.

Author: nikic

ext/gmp/gmp.c

@@ -1484,10 +1484,9 @@ ZEND_FUNCTION(gmp_powm)
 	FETCH_GMP_ZVAL_DEP_DEP(gmpnum_mod, mod_arg, temp_mod, temp_exp, temp_base);
 
 	if (!mpz_cmp_ui(gmpnum_mod, 0)) {
+		php_error_docref(NULL TSRMLS_CC, E_WARNING, "Modulus may not be zero");
 		FREE_GMP_TEMP(temp_base);
-		if (use_ui) {
-			FREE_GMP_TEMP(temp_exp);
-		}
+		FREE_GMP_TEMP(temp_exp);
 		FREE_GMP_TEMP(temp_mod);
 		RETURN_FALSE;
 	}

ext/gmp/tests/016.phpt

@@ -19,6 +19,9 @@ var_dump(gmp_strval(gmp_powm($n,$e,1000)));
 $m = gmp_init(900);
 var_dump(gmp_strval(gmp_powm($n,$e,$m)));
 
+var_dump(gmp_powm(5, 11, 0));
+var_dump(gmp_powm(5, "11", gmp_init(0)));
+
 var_dump(gmp_powm(array(),$e,$m));
 var_dump(gmp_powm($n,array(),$m));
 var_dump(gmp_powm($n,$e,array()));
@@ -46,6 +49,12 @@ string(3) "331"
 string(3) "171"
 string(3) "371"
 
+Warning: gmp_powm(): Modulus may not be zero in %s on line %d
+bool(false)
+
+Warning: gmp_powm(): Modulus may not be zero in %s on line %d
+bool(false)
+
 Warning: gmp_powm(): Unable to convert variable to GMP - wrong type in %s on line %d
 bool(false)