From 4a62318422ca3f0f72b6fd00031daba556a10687 Mon Sep 17 00:00:00 2001
From: Werner Koch <wk@gnupg.org>
Date: Wed, 4 Dec 2024 15:32:40 +0100
Subject: Add a configure test for gettid.

* configure.ac (HAVE_GETTID,HAVE_SYS_GETTID): New test.
* src/debug.c: Include syscall.h if needed.
(tid_log_callback) [HAVE_SYS_GETTID]: Use SYS_gettid
--

Linux introduced the gettid syscall with 2.4.11 but glibc only with
its version 2.30.  This patch allows building on older platforms.

Co-authored-by: lgh1
---
 src/debug.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

(limited to 'src')

diff --git a/src/debug.c b/src/debug.c
index 2a87305b..370f613c 100644
--- a/src/debug.c
+++ b/src/debug.c
@@ -29,6 +29,9 @@
 #ifdef HAVE_UNISTD_H
 # include <unistd.h>
 #endif
+#if defined(__linux) && defined(HAVE_SYS_GETTID)
+# include <syscall.h>
+#endif
 #include <ctype.h>
 #include <errno.h>
 #include <time.h>
@@ -147,12 +150,16 @@ static int
 tid_log_callback (unsigned long *rvalue)
 {
   int len = sizeof (*rvalue);
-  uintptr_t thread;
+  uintptr_t thread = 0;
 
 #ifdef HAVE_W32_SYSTEM
   thread = (uintptr_t)GetCurrentThreadId ();
 #elif defined(__linux)
-  thread = (uintptr_t)gettid ();
+#  ifdef HAVE_GETTID
+     thread = (uintptr_t)gettid ();
+#  elif defined(HAVE_SYS_GETTID)
+     thread = (uintptr_t)syscall(SYS_gettid);
+#  endif
 #endif
   if (sizeof (thread) < len)
     {
-- 
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