debug.h: Avoid printing pthread_t type

Using %lu for pthread_t was wrong on armv7l arch. Even worse, according
to pthread_self() man page, pthread_t cannot be assumed to be of a simple
type and hence printable:
"""
POSIX.1 allows an implementation wide freedom in choosing the type used
to represent a thread ID; for example, representation using either an
arithmetic  type  or a structure is permitted.
"""

Let's use gettid() instead. According to glibc documentation:
"""
The pid_t data type is a signed integer type which is capable of
representing a process ID. In the GNU C Library, this is an int.
"""
It may not be the same on other libc's though, so let's better cast to a
long int just in case.

Accordign to gettid() man, the libc function was only added recently
during glibc 2.30, however the system call has been around for quite
some time (linux 2.4.11). Let's accomodate use udner non-glibc or older
versions of it by having a direct syscall fallback.

Change-Id: I40265fd4c62e550014ba3ff3335ca053c5bc01f2

CommonLibs/debug.c

@@ -21,7 +21,17 @@
  * See the COPYING file in the main directory for details.
  */
 
-#include <pthread.h>
+#include "config.h"
+
+/* If HAVE_GETTID, then "_GNU_SOURCE" may need to be defined to use gettid() */
+#if HAVE_GETTID
+#define _GNU_SOURCE
+#endif
+
+#include <sys/types.h>
+#include <unistd.h>
+#include <sys/syscall.h>
+#include "config.h"
 
 #include <osmocom/core/logging.h>
 #include <osmocom/core/utils.h>
@@ -77,3 +87,15 @@ const struct log_info log_info = {
 	.cat = default_categories,
 	.num_cat = ARRAY_SIZE(default_categories),
 };
+
+pid_t my_gettid(void)
+{
+#if HAVE_GETTID
+	return gettid();
+#elif defined(LINUX) && defined(__NR_gettid)
+	return (pid_t) syscall(__NR_gettid);
+#else
+	#pragma message ("use pid as tid")
+	return getpid();
+#endif
+}

CommonLibs/debug.h

@@ -1,7 +1,7 @@
 #pragma once
 
 #include <stdbool.h>
-#include <pthread.h>
+#include <sys/types.h>
 
 #include <osmocom/core/logging.h>
 
@@ -18,10 +18,12 @@ enum {
 	DDEVDRV,
 };
 
+pid_t my_gettid(void);
+
 #define CLOGC(category, level, fmt, args...) do { \
-	LOGP(category, level, "[tid=%lu] " fmt, pthread_self(), ##args);  \
+	LOGP(category, level, "[tid=%ld] " fmt, (long int) my_gettid(), ##args);  \
 } while(0)
 
 #define CLOGCHAN(chan, category, level, fmt, args...) do { \
-	LOGP(category, level, "[tid=%lu][chan=%lu] " fmt, pthread_self(), chan, ##args);  \
+	LOGP(category, level, "[tid=%ld][chan=%lu] " fmt, (long int) my_gettid(), chan, ##args);  \
 } while(0)

configure.ac

@@ -75,6 +75,15 @@ AC_TYPE_SIZE_T
 AC_HEADER_TIME
 AC_C_BIGENDIAN
 
+# Check if gettid is available (despite not being documented in glibc doc, it requires __USE_GNU on some systems)
+# C compiler is used since __USE_GNU seems to be always defined for g++.
+save_CPPFLAGS=$CPPFLAGS
+AC_LANG_PUSH(C)
+CPPFLAGS="$CPPFLAGS -D_GNU_SOURCE"
+AC_CHECK_FUNCS([gettid])
+AC_LANG_POP(C)
+CPPFLAGS=$save_CPPFLAGS
+
 PKG_CHECK_MODULES(LIBOSMOCORE, libosmocore >= 1.3.0)
 PKG_CHECK_MODULES(LIBOSMOVTY, libosmovty >= 1.3.0)
 PKG_CHECK_MODULES(LIBOSMOCTRL, libosmoctrl >= 1.3.0)