Use native gettid() if available (which is the case on Android).

configure.in

@@ -380,15 +380,19 @@ dnl check if native rwlocks are available
 AC_CHECK_FUNCS(pthread_rwlock_init)
 LIBS=$saved_LIBS
 
-AC_MSG_CHECKING([for gettid])
-AC_TRY_COMPILE(
-	[#define _GNU_SOURCE
-	#include <unistd.h>
-	#include <sys/syscall.h>],
-	[int main() {
-		return syscall(SYS_gettid);}],
-	[AC_MSG_RESULT([yes]); AC_DEFINE([HAVE_GETTID])],
-	[AC_MSG_RESULT([no])]
+AC_CHECK_FUNC(
+	[gettid],
+	[AC_DEFINE(HAVE_GETTID)],
+	[AC_MSG_CHECKING([for SYS_gettid])
+	 AC_TRY_COMPILE(
+		[#define _GNU_SOURCE
+		 #include <unistd.h>
+		 #include <sys/syscall.h>],
+		[int main() {
+			return syscall(SYS_gettid);}],
+		[AC_MSG_RESULT([yes]); AC_DEFINE([HAVE_SYS_GETTID])],
+		[AC_MSG_RESULT([no])]
+	)]
 )
 
 AC_CHECK_FUNCS(prctl mallinfo getpass closefrom)

src/libstrongswan/threading/thread.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2009-2011 Tobias Brunner
+ * Copyright (C) 2009-2012 Tobias Brunner
  * Hochschule fuer Technik Rapperswil
  *
  * This program is free software; you can redistribute it and/or modify it
@@ -17,10 +17,18 @@
 #include <pthread.h>
 #include <signal.h>
 #include <semaphore.h>
+
 #ifdef HAVE_GETTID
+#include <sys/types.h>
+#elif defined(HAVE_SYS_GETTID)
 #include <unistd.h>
 #include <sys/syscall.h>
-#endif
+static inline pid_t gettid()
+{
+	return syscall(SYS_gettid);
+}
+#define HAVE_GETTID
+#endif /* HAVE_SYS_GETTID */
 
 #include <library.h>
 #include <debug.h>
@@ -287,7 +295,7 @@ static void *thread_main(private_thread_t *this)
 	 * could be of any size, or even a struct) */
 #ifdef HAVE_GETTID
 	DBG2(DBG_LIB, "created thread %.2d [%u]",
-		 this->id, syscall(SYS_gettid));
+		 this->id, gettid());
 #else
 	DBG2(DBG_LIB, "created thread %.2d [%lx]",
 		 this->id, (u_long)this->thread_id);