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

[Jinsong Ji via cfe-commits]

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

None

>From 7d8157357b4b9ba1462e0b4d0fafa7650d7f6b40 Mon Sep 17 00:00:00 2001
From: Jinsong Ji <jinsong.ji at intel.com>
Date: Wed, 5 Mar 2025 11:49:19 -0800
Subject: [PATCH] c-index-test: fix buffer overflow

---
 clang/tools/c-index-test/c-index-test.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

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;