Ensure _dosmaperr() actually sets errno correctly.

If logging is enabled, either ereport() or fprintf() might stomp on errno
internally, causing this function to return the wrong result.  That might
only end in a misleading error report, but in any code that's examining
errno to decide what to do next, the consequences could be far graver.

This has been broken since the very first version of this file in 2006
... it's a bit astonishing that we didn't identify this long ago.

Reported by Amit Kapila, though this isn't his proposed fix.

diff --git a/src/port/win32error.c b/src/port/win32error.c
index 2222be89071839417f571cfda3c0a118183c9e3d..5c49b38a5e70cf72a43acdc7d06eedd8dc78353f 100644 (file)
--- a/src/port/win32error.c
+++ b/src/port/win32error.c
@@ -179,14 +179,16 @@ _dosmaperr(unsigned long e)
        {
                if (doserrors[i].winerr == e)
                {
-                       errno = doserrors[i].doserr;
+                       int                     doserr = doserrors[i].doserr;
+
 #ifndef FRONTEND
                        ereport(DEBUG5,
                                        (errmsg_internal("mapped win32 error code %lu to %d",
-                                                                        e, errno)));
+                                                                        e, doserr)));
 #elif FRONTEND_DEBUG
-                       fprintf(stderr, _("mapped win32 error code %lu to %d"), e, errno);
+                       fprintf(stderr, _("mapped win32 error code %lu to %d"), e, doserr);
 #endif
+                       errno = doserr;
                        return;
                }
        }