[libcxx] r272640 - Fix error checking for strerror_r implementations that return the error code.

[Eric Fiselier via cfe-commits]

Author: ericwf
Date: Tue Jun 14 01:03:20 2016
New Revision: 272640

URL: http://llvm.org/viewvc/llvm-project?rev=272640&view=rev
Log:
Fix error checking for strerror_r implementations that return the error code.

Modified:
    libcxx/trunk/src/system_error.cpp

Modified: libcxx/trunk/src/system_error.cpp
URL: http://llvm.org/viewvc/llvm-project/libcxx/trunk/src/system_error.cpp?rev=272640&r1=272639&r2=272640&view=diff
==============================================================================
--- libcxx/trunk/src/system_error.cpp (original)
+++ libcxx/trunk/src/system_error.cpp Tue Jun 14 01:03:20 2016
@@ -70,8 +70,10 @@ string do_strerror_r(int ev) {
 string do_strerror_r(int ev) {
     char buffer[strerror_buff_size];
     const int old_errno = errno;
-    if (::strerror_r(ev, buffer, strerror_buff_size) == -1) {
-        const int new_errno = errno;
+    if ((int ret = ::strerror_r(ev, buffer, strerror_buff_size)) != 0) {
+        // If `ret == -1` then the error is specified using `errno`, otherwise
+        // `ret` represents the error.
+        const int new_errno = ret == -1 ? errno : ret;
         errno = old_errno;
         if (new_errno == EINVAL) {
             std::snprintf(buffer, strerror_buff_size, "Unknown error %d", ev);