__thread --> thread_local for C11 compat

Also make thread_local available w/o including <threads.h>.
(as the latter hasn't been implemented, but this part is trivial)

src/shared/capability.c

@@ -55,8 +55,8 @@ int have_effective_cap(int value) {
 }
 
 unsigned long cap_last_cap(void) {
-        static __thread unsigned long saved;
-        static __thread bool valid = false;
+        static thread_local unsigned long saved;
+        static thread_local bool valid = false;
         unsigned long p;
 
         if (valid)

src/shared/cgroup-util.c

@@ -480,7 +480,7 @@ static int join_path(const char *controller, const char *path, const char *suffi
 
 int cg_get_path(const char *controller, const char *path, const char *suffix, char **fs) {
         const char *p;
-        static __thread bool good = false;
+        static thread_local bool good = false;
 
         assert(fs);
 

src/shared/macro.h

@@ -300,5 +300,17 @@ do {                                                                    \
                 _found;                                                 \
         })
 
+/* Define C11 thread_local attribute even on older compilers */
+#ifndef thread_local
+/*
+ * Don't break on glibc < 2.16 that doesn't define __STDC_NO_THREADS__
+ * see http://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
 
 #include "log.h"

src/shared/util.c

@@ -86,7 +86,7 @@ static volatile unsigned cached_columns = 0;
 static volatile unsigned cached_lines = 0;
 
 size_t page_size(void) {
-        static __thread size_t pgsz = 0;
+        static thread_local size_t pgsz = 0;
         long r;
 
         if (_likely_(pgsz > 0))
@@ -4580,7 +4580,7 @@ char *strjoin(const char *x, ...) {
 }
 
 bool is_main_thread(void) {
-        static __thread int cached = 0;
+        static thread_local int cached = 0;
 
         if (_unlikely_(cached == 0))
                 cached = getpid() == gettid() ? 1 : -1;
@@ -4798,7 +4798,7 @@ static const char *const __signal_table[] = {
 DEFINE_PRIVATE_STRING_TABLE_LOOKUP(__signal, int);
 
 const char *signal_to_string(int signo) {
-        static __thread char buf[sizeof("RTMIN+")-1 + DECIMAL_STR_MAX(int) + 1];
+        static thread_local char buf[sizeof("RTMIN+")-1 + DECIMAL_STR_MAX(int) + 1];
         const char *name;
 
         name = __signal_to_string(signo);

src/shared/virt.c

@@ -150,8 +150,8 @@ static int detect_vm_dmi(const char **_id) {
 /* Returns a short identifier for the various VM implementations */
 int detect_vm(const char **id) {
         _cleanup_free_ char *hvtype = NULL, *cpuinfo_contents = NULL;
-        static __thread int cached_found = -1;
-        static __thread const char *cached_id = NULL;
+        static thread_local int cached_found = -1;
+        static thread_local const char *cached_id = NULL;
         const char *_id = NULL;
         int r;
 
@@ -215,8 +215,8 @@ finish:
 
 int detect_container(const char **id) {
 
-        static __thread int cached_found = -1;
-        static __thread const char *cached_id = NULL;
+        static thread_local int cached_found = -1;
+        static thread_local const char *cached_id = NULL;
 
         _cleanup_free_ char *e = NULL;
         const char *_id = NULL;