api: fix infinite loop in function string_replace when the search string is empty

CHANGELOG.md

@@ -20,6 +20,7 @@ SPDX-License-Identifier: GPL-3.0-or-later
 ### Fixed
 
 - core: fix option weechat.look.color_real_white not applied when color is "white" on 16+ colors terminals ([#1742](https://github.com/weechat/weechat/issues/1742))
+- api: fix infinite loop in function string_replace when the search string is empty
 - irc: fix tag in message with list of names when joining a channel
 - fset: remove error displayed in core buffer when clicking with the mouse below the last option displayed
 - irc: limit size of data received from the server to prevent memory exhaustion

src/core/core-string.c

@@ -1966,6 +1966,9 @@ string_replace (const char *string, const char *search, const char *replace)
     if (!string || !search || !replace)
         return NULL;
 
+    if (!search[0])
+        return strdup (string);
+
     length1 = strlen (search);
     length2 = strlen (replace);
 

tests/unit/core/test-core-string.cpp

@@ -1454,6 +1454,8 @@ TEST(CoreString, Replace)
     WEE_TEST_STR(NULL, string_replace ("string", NULL, "replace"));
     WEE_TEST_STR(NULL, string_replace (NULL, "search", "replace"));
 
+    WEE_TEST_STR("test abc def", string_replace("test abc def", "", "xxx"));
+
     WEE_TEST_STR("test abc def", string_replace("test abc def", "xyz", "xxx"));
     WEE_TEST_STR("test xxx def", string_replace("test abc def", "abc", "xxx"));
     WEE_TEST_STR("xxx test xxx def xxx",