[clang-tools-extra] [clang-tidy] Do not flag strerror in concurrency-mt-unsafe (PR #140520)

[Carlos Galvez via cfe-commits]

https://github.com/carlosgalvezp created https://github.com/llvm/llvm-project/pull/140520

The docs of the check state:

> Glibc’s list is compiled from GNU web documentation with a search for MT-Safe tag

And strerror fulfills exactly that: https://www.gnu.org/software/libc/manual/html_node/Error-Messages.html

> Function: char * strerror (int errnum)
> Preliminary: | MT-Safe | AS-Unsafe heap i18n | AC-Unsafe mem | See POSIX Safety Concepts.

So concurrency-mt-unsafe should not flag it.

Fixes #140515

>From 35769db674fc2ebe7c0dda9ed329806b8b059414 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Carlos=20G=C3=A1lvez?= <carlos.galvez at zenseact.com>
Date: Mon, 19 May 2025 09:35:30 +0000
Subject: [PATCH] [clang-tidy] Do not flag strerror in concurrency-mt-unsafe
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

The docs of the check state:

> Glibc’s list is compiled from GNU web documentation with a search for MT-Safe tag

And strerror fulfills exactly that: https://www.gnu.org/software/libc/manual/html_node/Error-Messages.html

> Function: char * strerror (int errnum)
> Preliminary: | MT-Safe | AS-Unsafe heap i18n | AC-Unsafe mem | See POSIX Safety Concepts.

So concurrency-mt-unsafe should not flag it.

Fixes #140515
---
 clang-tools-extra/clang-tidy/concurrency/MtUnsafeCheck.cpp    | 1 -
 clang-tools-extra/docs/ReleaseNotes.rst                       | 4 ++++
 .../test/clang-tidy/checkers/concurrency/mt-unsafe-glibc.cpp  | 3 +++
 3 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/clang-tools-extra/clang-tidy/concurrency/MtUnsafeCheck.cpp b/clang-tools-extra/clang-tidy/concurrency/MtUnsafeCheck.cpp
index acffaa30d418e..cf076bb40484f 100644
--- a/clang-tools-extra/clang-tidy/concurrency/MtUnsafeCheck.cpp
+++ b/clang-tools-extra/clang-tidy/concurrency/MtUnsafeCheck.cpp
@@ -153,7 +153,6 @@ static const clang::StringRef GlibcFunctions[] = {
     "::sigsuspend",
     "::sleep",
     "::srand48",
-    "::strerror",
     "::strsignal",
     "::strtok",
     "::tcflow",
diff --git a/clang-tools-extra/docs/ReleaseNotes.rst b/clang-tools-extra/docs/ReleaseNotes.rst
index 9b29ab12e1bfa..bd78b26b583c8 100644
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/clang-tools-extra/docs/ReleaseNotes.rst
@@ -172,6 +172,10 @@ Changes in existing checks
   <clang-tidy/checks/cert/err33-c>` check by fixing false positives when
   a function name is just prefixed with a targeted function name.
 
+- Improved :doc:`concurrency-mt-unsafe
+  <clang-tidy/checks/concurrency/mt-unsafe>` check by fixing a false positive
+  where `strerror` was flagged as MT-unsafe.
+
 - Improved :doc:`misc-const-correctness
   <clang-tidy/checks/misc/const-correctness>` check by adding the option
   `AllowedTypes`, that excludes specified types from const-correctness
diff --git a/clang-tools-extra/test/clang-tidy/checkers/concurrency/mt-unsafe-glibc.cpp b/clang-tools-extra/test/clang-tidy/checkers/concurrency/mt-unsafe-glibc.cpp
index 8b137de005a47..14d1912683795 100644
--- a/clang-tools-extra/test/clang-tidy/checkers/concurrency/mt-unsafe-glibc.cpp
+++ b/clang-tools-extra/test/clang-tidy/checkers/concurrency/mt-unsafe-glibc.cpp
@@ -3,6 +3,7 @@
 extern unsigned int sleep (unsigned int __seconds);
 extern int *gmtime (const int *__timer);
 extern char *dirname (char *__path);
+extern char *strerror(int errnum);
 
 void foo() {
   sleep(2);
@@ -12,4 +13,6 @@ void foo() {
   // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: function is not thread safe [concurrency-mt-unsafe]
 
   dirname(nullptr);
+
+  strerror(0);
 }