Add error reporting (via errno) to getauxval().

[BZ 15846] As discussed in the recent thread on my $EXEC_ORIGIN patch
and in BZ 15846, getauxval() presently has no unambiguous way of
reporting an error condition.  It currently returns zero on error, but
this may also be a valid result for some auxv entries.  As there is no
clear invalid result for all current and future auxv entries, this patch
sets errno (following a suggestion in the BZ entry).

This version of the patch also adds documentation and tests for the
value-not-found conditions in getauxval().

1 files changed, 3 insertions, 0 deletions

diff --git a/misc/getauxval.c b/misc/getauxval.c
index e0317fd6f9..dd4c8ecab3 100644
--- a/misc/getauxval.c
+++ b/misc/getauxval.c
@@ -16,6 +16,7 @@
    <http://www.gnu.org/licenses/>.  */
 
 #include <sys/auxv.h>
+#include <errno.h>
 #include <ldsodefs.h>
 
 
@@ -32,6 +33,8 @@ __getauxval (unsigned long int type)
   for (p = GLRO(dl_auxv); p->a_type != AT_NULL; p++)
     if (p->a_type == type)
       return p->a_un.a_val;
+
+  __set_errno (ENOENT);
   return 0;
 }