From: Dmitry Stogov <dmitry@zend.com>
Date: Thu, 26 Oct 2017 06:45:02 +0000 (+0300)
Subject: Avoid reallocations when concatenate with empty string
X-Git-Tag: php-7.3.0alpha1~1169
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=886d4d9ca113ea24b373ee7b0fa8b2c5235be9ae;p=php

Avoid reallocations when concatenate with empty string
---

diff --git a/Zend/zend_operators.c b/Zend/zend_operators.c
index 5270b6b39a..1449405b43 100644
--- a/Zend/zend_operators.c
+++ b/Zend/zend_operators.c
@@ -1744,7 +1744,18 @@ ZEND_API int ZEND_FASTCALL concat_function(zval *result, zval *op1, zval *op2) /
 		}
 	} while (0);
 
-	{
+	if (UNEXPECTED(Z_STRLEN_P(op1) == 0)) {
+		if (EXPECTED(result != op2)) {
+			if (result == orig_op1) {
+				zval_dtor(orig_op1);
+			}
+			ZVAL_COPY(result, op2);
+		}
+	} else if (UNEXPECTED(Z_STRLEN_P(op2) == 0)) {
+		if (EXPECTED(result != op1)) {
+			ZVAL_COPY(result, op1);
+		}
+	} else {
 		size_t op1_len = Z_STRLEN_P(op1);
 		size_t op2_len = Z_STRLEN_P(op2);
 		size_t result_len = op1_len + op2_len;