From 052d5889f871f792def285c92bd91182d07789cd Mon Sep 17 00:00:00 2001
From: Christian Ulmann <christianulmann@gmail.com>
Date: Fri, 6 Jun 2025 11:24:46 +0200
Subject: [PATCH] [Support] Properly zero initialize CPU set when querying
 affinity (#142924)

This commit resolves a potential issue of working with uninitialized
memory when querying the CPU's affinity. The man page of
`sched_getaffinity` does not guarantee that the memory will be fully
overwritten, so this change should ensure that issues are avoided.
---
 llvm/lib/Support/Unix/Threading.inc | 1 +
 1 file changed, 1 insertion(+)

diff --git a/llvm/lib/Support/Unix/Threading.inc b/llvm/lib/Support/Unix/Threading.inc
index 742660d5bea7..562971aae32f 100644
--- a/llvm/lib/Support/Unix/Threading.inc
+++ b/llvm/lib/Support/Unix/Threading.inc
@@ -318,6 +318,7 @@ static int computeHostNumHardwareThreads() {
     return CPU_COUNT(&mask);
 #elif defined(__linux__)
   cpu_set_t Set;
+  CPU_ZERO(&Set);
   if (sched_getaffinity(0, sizeof(Set), &Set) == 0)
     return CPU_COUNT(&Set);
 #endif