[PATCH 02/16] libelf: Make elf_version thread-safe

[Mark Wielaard]

From: Heather McIntyre <hsm2@rice.edu>

	* elf_version.c (version_once): Define once.
	(initialize_version): New static function.
	(elf_version): Use initialize_version version_once.

Signed-off-by: Heather S. McIntyre <hsm2@rice.edu>
Signed-off-by: Mark Wielaard <mark@klomp.org>
---
 libelf/elf_version.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/libelf/elf_version.c b/libelf/elf_version.c
index 6ec534ab..8296bb65 100644
--- a/libelf/elf_version.c
+++ b/libelf/elf_version.c
@@ -32,12 +32,21 @@
 #endif
 
 #include <libelfP.h>
+#include <pthread.h>
 
+/* Multiple threads may initialize __libelf_version.
+   pthread_once() ensures that __libelf_version is initialized only once. */
+once_define(static, version_once);
 
 /* Currently selected version.  Should be EV_CURRENT.
    Will be EV_NONE if elf_version () has not been called yet.  */
 unsigned int __libelf_version = EV_NONE;
 
+static void initialize_version(void)
+{
+  __libelf_version = EV_CURRENT;
+}
+
 unsigned int
 elf_version (unsigned int version)
 {
@@ -49,7 +58,7 @@ elf_version (unsigned int version)
       /* Phew, we know this version.  */
 
       /* Signal that the version is now initialized.  */
-      __libelf_version = EV_CURRENT;
+      once(version_once, initialize_version);
 
       /* And return the last (or initial) version.  */
       return EV_CURRENT;
-- 
2.41.0