Zend/zend_operators: fix casting underflowed unsigend to signed

Casting a huge unsigned value to signed is undefined behavior in C.
We need to cast to signed before subtracting.

In case anybody worries about truncating a 64 bit size_t to 32 bit int
too early: this problem was there before already, this commit just
makes one corner case more likely.

Author: MaxKellermann

Zend/zend_operators.c

@@ -2956,7 +2956,7 @@ ZEND_API int ZEND_FASTCALL zend_binary_strcmp(const char *s1, size_t len1, const
 	}
 	retval = memcmp(s1, s2, MIN(len1, len2));
 	if (!retval) {
-		return (int)(len1 - len2);
+		return (int)len1 - (int)len2;
 	} else {
 		return retval;
 	}
@@ -2972,7 +2972,7 @@ ZEND_API int ZEND_FASTCALL zend_binary_strncmp(const char *s1, size_t len1, cons
 	}
 	retval = memcmp(s1, s2, MIN(length, MIN(len1, len2)));
 	if (!retval) {
-		return (int)(MIN(length, len1) - MIN(length, len2));
+		return (int)MIN(length, len1) - (int)MIN(length, len2);
 	} else {
 		return retval;
 	}
@@ -2997,7 +2997,7 @@ ZEND_API int ZEND_FASTCALL zend_binary_strcasecmp(const char *s1, size_t len1, c
 		}
 	}
 
-	return (int)(len1 - len2);
+	return (int)len1 - (int)len2;
 }
 /* }}} */
 
@@ -3018,7 +3018,7 @@ ZEND_API int ZEND_FASTCALL zend_binary_strncasecmp(const char *s1, size_t len1,
 		}
 	}
 
-	return (int)(MIN(length, len1) - MIN(length, len2));
+	return (int)MIN(length, len1) - (int)MIN(length, len2);
 }
 /* }}} */
 
@@ -3040,7 +3040,7 @@ ZEND_API int ZEND_FASTCALL zend_binary_strcasecmp_l(const char *s1, size_t len1,
 		}
 	}
 
-	return (int)(len1 - len2);
+	return (int)len1 - (int)len2;
 }
 /* }}} */
 
@@ -3061,7 +3061,7 @@ ZEND_API int ZEND_FASTCALL zend_binary_strncasecmp_l(const char *s1, size_t len1
 		}
 	}
 
-	return (int)(MIN(length, len1) - MIN(length, len2));
+	return (int)MIN(length, len1) - (int)MIN(length, len2);
 }
 /* }}} */