* cygerrno.h (set_errno): Define more informative version of this function for

debugging.
(__set_errno): Declare when DEBUGGING.
* cygheap.h (cygheap_fdget::cygheap_fdget): Add a flag to control when errno is
set.
* debug.cc (__set_errno): New function.
* fcntl.cc (_fcntl): Fix so that correct fd is used for second argument to
dup2.
* syscalls.cc (_cygwin_istext_for_stdio): Don't set errno here when using
cygheap_fdget.

winsup/cygwin/fcntl.cc

@@ -41,13 +41,7 @@ _fcntl (int fd, int cmd,...)
   if (cmd != F_DUPFD)
     res = cfd->fcntl(cmd, arg);
   else
-    {
-      cygheap_fdnew newfd;
-      if (newfd >= 0)
-	res = dup2 (fd, newfd);
-      else
-	res = -1;
-    }
+    res = dup2 (fd, cygheap_fdnew (((int) arg) - 1));
   va_end (args);
 
 done: