[clang] c-index-test: fix buffer overflow (PR #129922)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Jinsong Ji (jsji)

<details>
<summary>Changes</summary>



---
Full diff: https://github.com/llvm/llvm-project/pull/129922.diff


1 Files Affected:

- (modified) clang/tools/c-index-test/c-index-test.c (+2-2) 


``````````diff
diff --git a/clang/tools/c-index-test/c-index-test.c b/clang/tools/c-index-test/c-index-test.c
index 942500f2975e4..eb1d3de09acd0 100644
--- a/clang/tools/c-index-test/c-index-test.c
+++ b/clang/tools/c-index-test/c-index-test.c
@@ -3555,11 +3555,11 @@ static CXIdxClientContainer makeClientContainer(CXClientData *client_data,
   clang_indexLoc_getFileLocation(loc, &file, 0, &line, &column, 0);
 
   len = sizeof(IndexDataStringList) + strlen(name) + digitCount(line) +
-        digitCount(column) + 2;
+        digitCount(column) + 3;
   node = (IndexDataStringList *)malloc(len);
   assert(node);
   newStr = node->data;
-  snprintf(newStr, len, "%s:%d:%d", name, line, column);
+  snprintf(newStr, len - sizeof(IndexDataStringList) , "%s:%d:%d", name, line, column);
 
   /* Remember string so it can be freed later. */
   index_data = (IndexData *)client_data;

``````````

</details>


https://github.com/llvm/llvm-project/pull/129922