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 41e8cd8bf352033f6f0f00bfa7490672d4004155..91386dd8af89324f007be51e1fb88aa2548ae00d 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;
                }
        }