lib: add utility function nl_strerror_l()

libnl currently uses strerror_r() throughout, but this is
problematic because there is a non-standard GNU version
implemented in glibc, and the standard POSIX version, which
differ in signature. When using glibc, one can choose
between the two versions using feature test macros
_GNU_SOURCE and _POSIX_C_SOURCE.

Given libnl is built using the former, we always get the
glibc special version, and all code so far has been written
for that non-standard version.

Other C libraries like musl on the other hand only try
to be posix compliant, and only ever provide the posix
version of strerror_r(), which has a different signature.

The alternative is to use strerror_l() rather than
strerror_r() http://austingroupbugs.net/view.php?id=655
- this will avoid the non-confirming versions issue
- strerror_l() is now recommended by POSIX to replace
  strerror_r() usage

So rather than changing all uses of strerror_r() to be in
line with posix, we are going to switch to the recommended
interface strerror_l().

Since strerror_l() is slightly more difficuly to use, we
add a little (private) wrapper that we can use from all
current callsites of strerror_r().

Signed-off-by: André Draszik <adraszik@tycoint.com>
Reviewed-by: Stephane Ayotte <sayotte@tycoint.com>
Signed-off-by: Thomas Haller <thaller@redhat.com>

1 files changed, 24 insertions, 0 deletions

diff --git a/lib/utils.c b/lib/utils.c
index 61c3d95..c1c1b72 100644
--- a/lib/utils.c
+++ b/lib/utils.c
@@ -25,10 +25,12 @@
  */
 
 #include <netlink-private/netlink.h>
+#include <netlink-private/utils.h>
 #include <netlink/netlink.h>
 #include <netlink/utils.h>
 #include <linux/socket.h>
 #include <stdlib.h> /* exit() */
+#include <locale.h>
 
 /**
  * Global variable indicating the desired level of debugging output.
@@ -118,6 +120,28 @@ int __nl_read_num_str_file(const char *path, int (*cb)(long, const char *))
 
 	return 0;
 }
+
+const char *nl_strerror_l(int err)
+{
+	int errno_save = errno;
+	locale_t loc = newlocale(LC_MESSAGES_MASK, "", (locale_t)0);
+	const char *buf;
+
+	if (loc == (locale_t)0) {
+		if (errno == ENOENT)
+			loc = newlocale(LC_MESSAGES_MASK,
+					"POSIX", (locale_t)0);
+	}
+	if (loc != (locale_t)0) {
+		buf = strerror_l(err, loc);
+		freelocale(loc);
+	} else {
+		buf = "newlocale() failed";
+	}
+
+	errno = errno_save;
+	return buf;
+}
 /** @endcond */
 
 /**