[compiler-rt] [MSan] Fix check overflow in a test case (PR #150429)

[Kunqiu Chen via llvm-commits]

https://github.com/Camsyn created https://github.com/llvm/llvm-project/pull/150429

Supplement to PR #144073

Previously, _msan_check_mem_is_initialized.cpp_ initialized a 32-byte stack array, but checked the shadow for the offset range [12, 42), exceeding the stack array size.

MSan does not guarantee that the shadow corresponding to the overflow part is 0, so it is undefined to require the overflow part to be unpoisoned.

>From 8e1761e72e399e84753e175ec8793cf1952393e1 Mon Sep 17 00:00:00 2001
From: Camsyn <camsyn at foxmail.com>
Date: Thu, 24 Jul 2025 22:06:32 +0800
Subject: [PATCH] [MSan] Fix check overflow in a test case

Previously, msan_check_mem_is_initialized.cpp initialized a stack array
with size of 32-byte, but check the shaodw for offset range [12, 42),
exceeding the stack array size.

MSan does not guarantee that the shadow corresponding to the overflow
part  is 0, so it is undefined to require the overflow part to be
unpoisoned
---
 compiler-rt/test/msan/msan_check_mem_is_initialized.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/compiler-rt/test/msan/msan_check_mem_is_initialized.cpp b/compiler-rt/test/msan/msan_check_mem_is_initialized.cpp
index aaf5737ebe236..aab31893e01bc 100644
--- a/compiler-rt/test/msan/msan_check_mem_is_initialized.cpp
+++ b/compiler-rt/test/msan/msan_check_mem_is_initialized.cpp
@@ -12,7 +12,7 @@ int main(void) {
   __msan_poison(p + 10, 2);
 
   __msan_check_mem_is_initialized(p, 10);
-  __msan_check_mem_is_initialized(p + 12, 30);
+  __msan_check_mem_is_initialized(p + 12, 20);
 #ifdef POSITIVE
   __msan_check_mem_is_initialized(p + 5, 20);
   // CHECK: Uninitialized bytes in __msan_check_mem_is_initialized at offset 5 inside [0x{{.*}}, 20)