getlogin_r: tweaks

[Bruno Haible]

This fixes a small bug in the m4/getlogin_r.m4 macros: The presence of a
getlogin_r() declaration in <unistd.h> depends on whether
AC_USE_SYSTEM_EXTENSIONS was already executed. And a tiny optimization
in lib/getlogin_r.c.


2010-01-09  Bruno Haible  <address@hidden>

        getlogin_r: Small fixes.
        * lib/getlogin_r.c (getlogin_r): Don't set errno if the function
        succeeds.
        * m4/getlogin_r.m4 (gl_GETLOGIN_R): Require gl_USE_SYSTEM_EXTENSIONS
        before testing whether getlogin_r is declared. No need to set
        HAVE_DECL_GETLOGIN_R to 1.
        (gl_PREREQ_GETLOGIN_R): Don't check for the getlogin_r declaration.

--- lib/getlogin_r.c.orig       Sat Jan  9 15:08:13 2010
+++ lib/getlogin_r.c    Sat Jan  9 15:07:43 2010
@@ -1,6 +1,6 @@
 /* Provide a working getlogin_r for systems which lack it.
 
-   Copyright (C) 2005, 2006, 2007, 2009, 2010 Free Software Foundation, Inc.
+   Copyright (C) 2005-2007, 2009-2010 Free Software Foundation, Inc.
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -39,15 +39,10 @@
 
   errno = 0;
   n = getlogin ();
-
-  /* A system function like getlogin_r is never supposed to set errno
-     to zero, so make sure errno is nonzero here.  ENOENT is a
-     reasonable errno value if getlogin returns NULL.  */
-  if (!errno)
-    errno = ENOENT;
-
   if (!n)
-    return errno;
+    /* ENOENT is a reasonable errno value if getlogin returns NULL.  */
+    return (errno != 0 ? errno : ENOENT);
+
   nlen = strlen (n);
   if (size <= nlen)
     return ERANGE;
--- m4/getlogin_r.m4.orig       Sat Jan  9 15:08:13 2010
+++ m4/getlogin_r.m4    Sat Jan  9 15:07:58 2010
@@ -1,6 +1,6 @@
-#serial 4
+#serial 5
 
-# Copyright (C) 2005, 2006, 2007, 2009, 2010 Free Software Foundation, Inc.
+# Copyright (C) 2005-2007, 2009-2010 Free Software Foundation, Inc.
 #
 # This file is free software; the Free Software Foundation
 # gives unlimited permission to copy and/or distribute it,
@@ -14,13 +14,16 @@
 AC_DEFUN([gl_GETLOGIN_R],
 [
   AC_REQUIRE([gl_UNISTD_H_DEFAULTS])
+
+  dnl Persuade glibc <unistd.h> to declare getlogin_r().
+  AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
+
   AC_CHECK_FUNCS_ONCE([getlogin_r])
   if test $ac_cv_func_getlogin_r = no; then
     AC_LIBOBJ([getlogin_r])
     gl_PREREQ_GETLOGIN_R
-    if test $ac_cv_have_decl_getlogin_r = yes; then
-      HAVE_DECL_GETLOGIN_R=1
-    else
+    AC_CHECK_DECLS_ONCE([getlogin_r])
+    if test $ac_cv_have_decl_getlogin_r = no; then
       HAVE_DECL_GETLOGIN_R=0
     fi
   fi
@@ -29,5 +32,4 @@
 AC_DEFUN([gl_PREREQ_GETLOGIN_R],
 [
   AC_CHECK_DECLS_ONCE([getlogin])
-  AC_CHECK_DECLS_ONCE([getlogin_r])
 ])