Fix error checking for strerror_r implementations that return the error code.

llvm-svn: 272640

1 files changed, 4 insertions, 2 deletions

diff --git a/libcxx/src/system_error.cpp b/libcxx/src/system_error.cpp
index 748b5f7..d7115fc 100644
--- a/libcxx/src/system_error.cpp
+++ b/libcxx/src/system_error.cpp
@@ -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);