Throw error for invalid characters for number base

This is about the situation where a character is not within the
specified number base. E.g. only 0-9, a-f are allowed for hexadecimal,
so what should `hexdec('z')` do?

In the past, such characters were silently ignored. Since PHP 7.4 a
deprecation notice would be generated. This commit changes that to a
ValueError.

Earlier RFC:
https://wiki.php.net/rfc/base_convert_improvements

Author: Sjoerd Langkemper

ext/standard/math.c

@@ -845,7 +845,7 @@ PHPAPI zend_long _php_math_basetolong(zval *arg, int base)
 /*
  * Convert a string representation of a base(2-36) number to a zval.
  */
-PHPAPI void _php_math_basetozval(zend_string *str, int base, zval *ret)
+PHPAPI zend_result _php_math_basetozval(zend_string *str, int base, zval *ret)
 {
 	zend_long num = 0;
 	double fnum = 0;
@@ -908,14 +908,16 @@ PHPAPI void _php_math_basetozval(zend_string *str, int base, zval *ret)
 	}
 
 	if (invalidchars > 0) {
-		zend_error(E_DEPRECATED, "Invalid characters passed for attempted conversion, these have been ignored");
+		zend_value_error("Invalid characters passed for attempted conversion");
+		return FAILURE;
 	}
 
 	if (mode == 1) {
 		ZVAL_DOUBLE(ret, fnum);
 	} else {
 		ZVAL_LONG(ret, num);
 	}
+	return SUCCESS;
 }
 /* }}} */
 
@@ -1033,7 +1035,9 @@ PHP_FUNCTION(bindec)
 		Z_PARAM_STR(arg)
 	ZEND_PARSE_PARAMETERS_END();
 
-	_php_math_basetozval(arg, 2, return_value);
+	if (SUCCESS != _php_math_basetozval(arg, 2, return_value)) {
+		RETURN_THROWS();
+	}
 }
 /* }}} */
 
@@ -1046,7 +1050,9 @@ PHP_FUNCTION(hexdec)
 		Z_PARAM_STR(arg)
 	ZEND_PARSE_PARAMETERS_END();
 
-	_php_math_basetozval(arg, 16, return_value);
+	if (SUCCESS != _php_math_basetozval(arg, 16, return_value)) {
+		RETURN_THROWS();
+	}
 }
 /* }}} */
 
@@ -1059,7 +1065,9 @@ PHP_FUNCTION(octdec)
 		Z_PARAM_STR(arg)
 	ZEND_PARSE_PARAMETERS_END();
 
-	_php_math_basetozval(arg, 8, return_value);
+	if (SUCCESS != _php_math_basetozval(arg, 8, return_value)) {
+		RETURN_THROWS();
+	}
 }
 /* }}} */
 
@@ -1136,7 +1144,10 @@ PHP_FUNCTION(base_convert)
 		RETURN_THROWS();
 	}
 
-	_php_math_basetozval(number, (int)frombase, &temp);
+	if (SUCCESS != _php_math_basetozval(number, (int)frombase, &temp)) {
+		RETURN_THROWS();
+	}
+
 	result = _php_math_zvaltobase(&temp, (int)tobase);
 	if (!result) {
 		RETURN_THROWS();

ext/standard/php_math.h

@@ -22,7 +22,7 @@ PHPAPI zend_string *_php_math_number_format_ex(double d, int dec, const char *de
 PHPAPI zend_string *_php_math_number_format_long(zend_long num, zend_long dec, const char *dec_point, size_t dec_point_len, const char *thousand_sep, size_t thousand_sep_len);
 PHPAPI zend_string * _php_math_longtobase(zend_long arg, int base);
 PHPAPI zend_long _php_math_basetolong(zval *arg, int base);
-PHPAPI void _php_math_basetozval(zend_string *str, int base, zval *ret);
+PHPAPI zend_result _php_math_basetozval(zend_string *str, int base, zval *ret);
 PHPAPI zend_string * _php_math_zvaltobase(zval *arg, int base);
 
 #include <math.h>