From 9f9964239e21d2e70df5ba1bf75fbdcc3c507cf0 Mon Sep 17 00:00:00 2001
From: Matthew Parkinson <mattpark@microsoft.com>
Date: Sun, 8 May 2022 20:32:52 +0100
Subject: [PATCH] Ensure logging doesn't affect errno

---
 src/snmalloc/pal/pal_posix.h | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/snmalloc/pal/pal_posix.h b/src/snmalloc/pal/pal_posix.h
index f71755d..58b3c1f 100644
--- a/src/snmalloc/pal/pal_posix.h
+++ b/src/snmalloc/pal/pal_posix.h
@@ -163,6 +163,9 @@ namespace snmalloc
      */
     static void message(const char* const str) noexcept
     {
+      // We don't want logging to affect the errno behaviour of the program.
+      auto hold = KeepErrno();
+
       void* nl = const_cast<char*>("\n");
       struct iovec iov[] = {{const_cast<char*>(str), strlen(str)}, {nl, 1}};
       UNUSED(writev(STDERR_FILENO, iov, sizeof(iov) / sizeof(struct iovec)));