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

CHANGELOG.md

@@ -8,6 +8,7 @@
 
 ### Fixed
 
+- api: fix infinite loop in function string_replace when the search string is empty
 - irc: limit size of data received from the server to prevent memory exhaustion
 - relay: limit size of received websocket frame and HTTP body to prevent memory exhaustion
 - relay: fix timing attack on password authentication ([GHSA-vhv8-g2r9-cwcc](https://github.com/weechat/weechat/security/advisories/GHSA-vhv8-g2r9-cwcc))

src/core/core-string.c

@@ -1959,6 +1959,9 @@ 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

@@ -1452,6 +1452,8 @@ 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",