Re: [bug-gnulib] New getlogin_r module

[Paul Eggert]

Derek Price <address@hidden> writes:

> It sets *and* returns errno since my local man pages make it sound
> like errno will be set by getlogin_r and others may already have
> code which checks errno and not getlogin_r's return value.

But glibc getlogin_r doesn't always set errno to the returned value,
and POSIX doesn't promise it, so such code is already broken.

> I would note that the opengroup POSIX spec you reference does not
> define an error return code for getlogin_r for the case where "the
> user's login name cannot be found".  I chose -1 arbitrarily.

We should return a valid errno value, since POSIX requires that
we return an error number, and -1 is not an error number.  Returning
ENOENT is fine.

A couple of other glitches I just noticed.  getlogin_r.h uses size_t
without necessarily defining it.  We shouldn't include <config.h>
without checking for HAVE_CONFIG_H.

I installed this change:

Index: lib/getlogin_r.h
===================================================================
RCS file: /cvsroot/gnulib/gnulib/lib/getlogin_r.h,v
retrieving revision 1.1
diff -p -u -r1.1 getlogin_r.h
--- lib/getlogin_r.h    25 May 2005 14:21:20 -0000      1.1
+++ lib/getlogin_r.h    25 May 2005 19:12:57 -0000
@@ -33,5 +33,6 @@
 
    See <http://www.opengroup.org/onlinepubs/009695399/functions/getlogin.html>.
  */
+# include <stddef.h>
 int getlogin_r (char *name, size_t size);
 #endif
Index: lib/getlogin_r.c
===================================================================
RCS file: /cvsroot/gnulib/gnulib/lib/getlogin_r.c,v
retrieving revision 1.1
diff -p -u -r1.1 getlogin_r.c
--- lib/getlogin_r.c    25 May 2005 14:21:20 -0000      1.1
+++ lib/getlogin_r.c    25 May 2005 19:12:57 -0000
@@ -18,7 +18,9 @@
 
 /* written by Paul Eggert and Derek Price */
 
-#include <config.h>
+#if HAVE_CONFIG_H
+# include <config.h>
+#endif
 
 #include "getlogin_r.h"
 
@@ -38,22 +40,15 @@ int
 getlogin_r (char *name, size_t size)
 {
   char *n;
-  int save_errno = errno;
+  size_t nlen;
 
   errno = 0;
   n = getlogin ();
-  if (n)
-    {
-      size_t nlen = strlen (n);
-      if (nlen < size)
-        {
-          memcpy (name, n, nlen + 1);
-          return 0;
-        }
-      errno = ERANGE;
-    }
-
-  if (errno) return errno;
-  errno = save_errno;
-  return -1;
+  if (!n)
+    return errno ? errno : ENOENT;
+  nlen = strlen (n);
+  if (size <= nlen)
+    return ERANGE;
+  memcpy (name, n, nlen + 1);
+  return 0;
 }