Include <threads.h> if possible to get thread_local definition

IN C23, thread_local is a reserved keyword and we shall therefore
do nothing to redefine it. glibc has it defined for older standard
version with the right conditions.

v2 by Yu Watanabe:
Move the definition to missing_threads.h like the way we define e.g.
missing syscalls or missing definitions, and include it by the users.

Co-authored-by: Yu Watanabe <watanabe.yu+github@gmail.com>

meson.build

@@ -756,6 +756,7 @@ foreach header : ['crypt.h',
                   'linux/memfd.h',
                   'linux/vm_sockets.h',
                   'sys/auxv.h',
+                  'threads.h',
                   'valgrind/memcheck.h',
                   'valgrind/valgrind.h',
                   'linux/time_types.h',

src/basic/capability-util.c

@@ -14,6 +14,7 @@
 #include "logarithm.h"
 #include "macro.h"
 #include "missing_prctl.h"
+#include "missing_threads.h"
 #include "parse-util.h"
 #include "user-util.h"
 

src/basic/cgroup-util.c

@@ -23,6 +23,7 @@
 #include "login-util.h"
 #include "macro.h"
 #include "missing_magic.h"
+#include "missing_threads.h"
 #include "mkdir.h"
 #include "parse-util.h"
 #include "path-util.h"

src/basic/log.c

@@ -25,6 +25,7 @@
 #include "log.h"
 #include "macro.h"
 #include "missing_syscall.h"
+#include "missing_threads.h"
 #include "parse-util.h"
 #include "proc-cmdline.h"
 #include "process-util.h"

src/basic/macro.h

@@ -297,20 +297,6 @@ static inline int __coverity_check_and_return__(int condition) {
              p != (typeof(p)) POINTER_MAX;                                               \
              p = *(++_l))
 
-/* Define C11 thread_local attribute even on older gcc compiler
- * version */
-#ifndef thread_local
-/*
- * Don't break on glibc < 2.16 that doesn't define __STDC_NO_THREADS__
- * see https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53769
- */
-#if __STDC_VERSION__ >= 201112L && !(defined(__STDC_NO_THREADS__) || (defined(__GNU_LIBRARY__) && __GLIBC__ == 2 && __GLIBC_MINOR__ < 16))
-#define thread_local _Thread_local
-#else
-#define thread_local __thread
-#endif
-#endif
-
 #define DEFINE_TRIVIAL_DESTRUCTOR(name, type, func)             \
         static inline void name(type *p) {                      \
                 func(p);                                        \

src/basic/memory-util.c

@@ -3,6 +3,7 @@
 #include <unistd.h>
 
 #include "memory-util.h"
+#include "missing_threads.h"
 
 size_t page_size(void) {
         static thread_local size_t pgsz = 0;

src/basic/missing_threads.h

@@ -0,0 +1,15 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+/* If threads.h doesn't exist, then define our own thread_local to match C11's thread_local. */
+#if HAVE_THREADS_H
+#  include <threads.h>
+#elif !(defined(thread_local))
+/* Don't break on glibc < 2.16 that doesn't define __STDC_NO_THREADS__
+ * see https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53769 */
+#  if __STDC_VERSION__ >= 201112L && !(defined(__STDC_NO_THREADS__) || (defined(__GNU_LIBRARY__) && __GLIBC__ == 2 && __GLIBC_MINOR__ < 16))
+#    define thread_local _Thread_local
+#  else
+#    define thread_local __thread
+#  endif
+#endif

src/basic/process-util.c

@@ -36,6 +36,7 @@
 #include "memory-util.h"
 #include "missing_sched.h"
 #include "missing_syscall.h"
+#include "missing_threads.h"
 #include "mountpoint-util.h"
 #include "namespace-util.h"
 #include "nulstr-util.h"

src/basic/psi-util.c

@@ -8,6 +8,7 @@
 #include "extract-word.h"
 #include "fd-util.h"
 #include "fileio.h"
+#include "missing_threads.h"
 #include "parse-util.h"
 #include "psi-util.h"
 #include "string-util.h"

src/basic/random-util.c

@@ -24,6 +24,7 @@
 #include "io-util.h"
 #include "missing_random.h"
 #include "missing_syscall.h"
+#include "missing_threads.h"
 #include "parse-util.h"
 #include "random-util.h"
 #include "sha256.h"

src/basic/signal-util.c

@@ -6,6 +6,7 @@
 #include "errno-util.h"
 #include "macro.h"
 #include "missing_syscall.h"
+#include "missing_threads.h"
 #include "parse-util.h"
 #include "signal-util.h"
 #include "stdio-util.h"

src/basic/time-util.c

@@ -17,6 +17,7 @@
 #include "io-util.h"
 #include "log.h"
 #include "macro.h"
+#include "missing_threads.h"
 #include "missing_timerfd.h"
 #include "parse-util.h"
 #include "path-util.h"

src/basic/virt.c

@@ -16,6 +16,7 @@
 #include "fd-util.h"
 #include "fileio.h"
 #include "macro.h"
+#include "missing_threads.h"
 #include "process-util.h"
 #include "stat-util.h"
 #include "string-table.h"

src/libsystemd/sd-bus/sd-bus.c

@@ -37,6 +37,7 @@
 #include "macro.h"
 #include "memory-util.h"
 #include "missing_syscall.h"
+#include "missing_threads.h"
 #include "parse-util.h"
 #include "path-util.h"
 #include "process-util.h"

src/libsystemd/sd-event/sd-event.c

@@ -24,6 +24,7 @@
 #include "memory-util.h"
 #include "missing_magic.h"
 #include "missing_syscall.h"
+#include "missing_threads.h"
 #include "path-util.h"
 #include "prioq.h"
 #include "process-util.h"

src/libsystemd/sd-id128/sd-id128.c

@@ -14,6 +14,7 @@
 #include "io-util.h"
 #include "macro.h"
 #include "missing_syscall.h"
+#include "missing_threads.h"
 #include "random-util.h"
 #include "stat-util.h"
 #include "user-util.h"

src/libsystemd/sd-resolve/sd-resolve.c

@@ -22,6 +22,7 @@
 #include "list.h"
 #include "memory-util.h"
 #include "missing_syscall.h"
+#include "missing_threads.h"
 #include "process-util.h"
 #include "resolve-private.h"
 #include "socket-util.h"

src/login/logind-inhibit.c

@@ -18,6 +18,7 @@
 #include "io-util.h"
 #include "logind-dbus.h"
 #include "logind-inhibit.h"
+#include "missing_threads.h"
 #include "mkdir-label.h"
 #include "parse-util.h"
 #include "path-util.h"

src/network/networkd-route-util.c

@@ -4,6 +4,7 @@
 
 #include "alloc-util.h"
 #include "logarithm.h"
+#include "missing_threads.h"
 #include "networkd-address.h"
 #include "networkd-link.h"
 #include "networkd-manager.h"

src/nss-systemd/nss-systemd.c

@@ -9,6 +9,7 @@
 #include "fd-util.h"
 #include "log.h"
 #include "macro.h"
+#include "missing_threads.h"
 #include "nss-systemd.h"
 #include "nss-util.h"
 #include "pthread-util.h"

src/shared/cgroup-setup.c

@@ -8,6 +8,7 @@
 #include "fd-util.h"
 #include "fileio.h"
 #include "fs-util.h"
+#include "missing_threads.h"
 #include "mkdir.h"
 #include "parse-util.h"
 #include "path-util.h"

src/shared/uid-alloc-range.c

@@ -3,6 +3,7 @@
 #include "chase-symlinks.h"
 #include "fd-util.h"
 #include "fileio.h"
+#include "missing_threads.h"
 #include "string-util.h"
 #include "uid-alloc-range.h"
 #include "user-util.h"