remove xgetdomainname module from Gnulib?

remove xgetdomainname module from Gnulib?

[Paul Eggert]

While looking into memory allocation issues I noticed the xgetdomainname 
module. As far as I know, nobody uses it, so I propose we remove it. The 
getdomainname function is used for the NIS domain name, and few programs 
would need that nowadays, as the world has mostly moved on to LDAP etc.

xgetdomainname was written by Simon Josefsson. I checked the GNU 
programs I thought he might be contributing to (GnuTLS, libtasn1, 
nettle, Emacs, inetutils) and xgetdomainname doesn't seem to be used 
there any more.

Re: remove xgetdomainname module from Gnulib?

[Simon Josefsson via Gnulib discussion list]

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Hi! I believe it is used by Shishi — https://www.gnu.org/software/shishi/manual/html_node/Utility-Functions.html — however I am sure it can be worked around by including the gnulib implementation directly. What problems does it cause to keep around? It is rather small.

/Simon

> 2 apr. 2021 kl. 02:39 skrev Paul Eggert <eggert@cs.ucla.edu>:
> 
> While looking into memory allocation issues I noticed the xgetdomainname module. As far as I know, nobody uses it, so I propose we remove it. The getdomainname function is used for the NIS domain name, and few programs would need that nowadays, as the world has mostly moved on to LDAP etc.
> 
> xgetdomainname was written by Simon Josefsson. I checked the GNU programs I thought he might be contributing to (GnuTLS, libtasn1, nettle, Emacs, inetutils) and xgetdomainname doesn't seem to be used there any more.

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Re: remove xgetdomainname module from Gnulib?

[Paul Eggert]

On 4/2/21 12:48 AM, Simon Josefsson wrote:
> Hi! I believe it is used by Shishi —https://www.gnu.org/software/shishi/manual/html_node/Utility-Functions.html  — however I am sure it can be worked around by including the gnulib implementation directly. What problems does it cause to keep around? It is rather small.

Thanks, if it's still used we'll keep it. The problem is minor: 
getdomainname should act like gethostname but the implementations have 
diverged because there are two copies of the relevant code. I can fix it 
by removing the divergence.

Re: remove xgetdomainname module from Gnulib?

[Paul Eggert]

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On 4/2/21 8:32 AM, Paul Eggert wrote:
> I can fix it by removing the divergence.

I did that by installing the attached, which causes xgetdomainname.c to 
be a couple of #defines followed by "#include "xgethostname.c".

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From 635076e47c7a000a11b3c2d173d5ef047fcf9af2 Mon Sep 17 00:00:00 2001
From: Paul Eggert <eggert@cs.ucla.edu>
Date: Sat, 3 Apr 2021 16:07:21 -0700
Subject: [PATCH] xgethostname: reorganize / simplify
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

xgethostname and xgetdomainname were essentially copies long
ago, but they’ve diverged.  Bring them back together again
by implementing the (rarely used) latter in terms of the former.
And avoid some unnecessary realloc calls while we’re at it.
* lib/xgetdomainname.c: Rewrite from scratch so that it merely
includes xgethostname.c with a few preliminaries.
* lib/xgethostname.c: Generalize so that it can be included
from xgetdomainname.c.
(GETANAME, XGETANAME): New macros.
(INITIAL_HOSTNAME_LENGTH): Remove.  No need for this parameter.
Use 100 instead, as few hostnames are longer than that.
(XGETANAME): Try getting the hostname into the stack first,
as that avoids a malloc call in the usual case.
Check for both POSIX-style truncation and SunOS 5.5 bug
in a cleaner way, by simply checking string length.
Don’t use x2realloc, which wastes time preserving buffer garbage;
use xpalloc with NULL instead.  Don’t bother shrinking buffer
in the very rare case where the hostname is longer than sizeof
buf; it’s not worth the aggravation.
* modules/xgetdomainname (Depends-on): Remove free-posix, xalloc.
Add xgethostname.
---
 ChangeLog              | 25 ++++++++++++
 lib/xgetdomainname.c   | 92 ++----------------------------------------
 lib/xgethostname.c     | 66 +++++++++++++-----------------
 modules/xgetdomainname |  3 +-
 4 files changed, 57 insertions(+), 129 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 956f6dd57..804e22897 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,28 @@
+2021-04-03  Paul Eggert  <eggert@cs.ucla.edu>
+
+	xgethostname: reorganize / simplify
+	xgethostname and xgetdomainname were essentially copies long
+	ago, but they’ve diverged.  Bring them back together again
+	by implementing the (rarely used) latter in terms of the former.
+	And avoid some unnecessary realloc calls while we’re at it.
+	* lib/xgetdomainname.c: Rewrite from scratch so that it merely
+	includes xgethostname.c with a few preliminaries.
+	* lib/xgethostname.c: Generalize so that it can be included
+	from xgetdomainname.c.
+	(GETANAME, XGETANAME): New macros.
+	(INITIAL_HOSTNAME_LENGTH): Remove.  No need for this parameter.
+	Use 100 instead, as few hostnames are longer than that.
+	(XGETANAME): Try getting the hostname into the stack first,
+	as that avoids a malloc call in the usual case.
+	Check for both POSIX-style truncation and SunOS 5.5 bug
+	in a cleaner way, by simply checking string length.
+	Don’t use x2realloc, which wastes time preserving buffer garbage;
+	use xpalloc with NULL instead.  Don’t bother shrinking buffer
+	in the very rare case where the hostname is longer than sizeof
+	buf; it’s not worth the aggravation.
+	* modules/xgetdomainname (Depends-on): Remove free-posix, xalloc.
+	Add xgethostname.
+
 2021-04-03  Bruno Haible  <bruno@clisp.org>
 
 	*-list tests: Add more tests.
diff --git a/lib/xgetdomainname.c b/lib/xgetdomainname.c
index d77c9b704..3c0aefd1d 100644
--- a/lib/xgetdomainname.c
+++ b/lib/xgetdomainname.c
@@ -1,89 +1,5 @@
-/* xgetdomainname.c -- Return the NIS domain name, without size limitations.
-   Copyright (C) 1992, 1996, 2000-2001, 2003-2004, 2006, 2008-2021 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
-   the Free Software Foundation; either version 3 of the License, or
-   (at your option) any later version.
-
-   This program is distributed in the hope that it will be useful,
-   but WITHOUT ANY WARRANTY; without even the implied warranty of
-   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-   GNU General Public License for more details.
-
-   You should have received a copy of the GNU General Public License
-   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
-
-/* Based on xgethostname.c, written by Jim Meyering.  */
-
-#include <config.h>
-
-/* Specification.  */
+/* Return the NIS domain name, without size limitations.  */
 #include "xgetdomainname.h"
-
-/* Get getdomainname.  */
-#include <unistd.h>
-
-/* Get errno.  */
-#include <errno.h>
-
-/* Get strlen.  */
-#include <string.h>
-
-/* Get free.  */
-#include <stdlib.h>
-
-#include "xalloc.h"
-
-#ifndef INITIAL_DOMAINNAME_LENGTH
-# define INITIAL_DOMAINNAME_LENGTH 34
-#endif
-
-/* Return the NIS domain name of the machine, in malloc'd storage.
-   WARNING! The NIS domain name is unrelated to the fully qualified host name
-            of the machine.  It is also unrelated to email addresses.
-   WARNING! The NIS domain name is usually the empty string or "(none)" when
-            not using NIS.
-   If malloc fails, exit.
-   Upon any other failure, set errno and return NULL.  */
-char *
-xgetdomainname (void)
-{
-  char *domainname;
-  size_t size;
-
-  size = INITIAL_DOMAINNAME_LENGTH;
-  domainname = xmalloc (size);
-  while (1)
-    {
-      int k = size - 1;
-      int err;
-
-      errno = 0;
-      domainname[k] = '\0';
-      err = getdomainname (domainname, size);
-      if (err >= 0 && domainname[k] == '\0')
-        break;
-      else if (err < 0 && errno != EINVAL)
-        {
-          free (domainname);
-          return NULL;
-        }
-      size *= 2;
-      domainname = xrealloc (domainname, size);
-    }
-
-  /* Shrink DOMAINNAME before returning it.  */
-  {
-    size_t actual_size = strlen (domainname) + 1;
-    if (actual_size < size)
-      {
-        char *shrinked_domainname = realloc (domainname, actual_size);
-        if (shrinked_domainname != NULL)
-          domainname = shrinked_domainname;
-      }
-  }
-
-  return domainname;
-}
+#define GETANAME getdomainname
+#define XGETANAME xgetdomainname
+#include "xgethostname.c"
diff --git a/lib/xgethostname.c b/lib/xgethostname.c
index 10e13de1d..87ae6dce8 100644
--- a/lib/xgethostname.c
+++ b/lib/xgethostname.c
@@ -16,12 +16,16 @@
    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
 
-/* written by Jim Meyering */
+/* written by Jim Meyering and Paul Eggert */
 
 #include <config.h>
 
+#ifndef GETANAME
 /* Specification.  */
-#include "xgethostname.h"
+# include "xgethostname.h"
+# define GETANAME gethostname
+# define XGETANAME xgethostname
+#endif
 
 #include <stdlib.h>
 #include <errno.h>
@@ -30,55 +34,39 @@
 
 #include "xalloc.h"
 
-#ifndef INITIAL_HOSTNAME_LENGTH
-# define INITIAL_HOSTNAME_LENGTH 34
-#endif
-
-/* Return the current hostname in malloc'd storage.
+/* Return the current host or domain name in malloc'd storage.
    If malloc fails, exit.
    Upon any other failure, return NULL and set errno.  */
 char *
-xgethostname (void)
+XGETANAME (void)
 {
-  char *hostname = NULL;
-  size_t size = INITIAL_HOSTNAME_LENGTH;
+  char buf[100];
+  idx_t size = sizeof buf;
+  char *name = buf;
+  char *alloc = NULL;
 
   while (1)
     {
       /* Use SIZE_1 here rather than SIZE to work around the bug in
          SunOS 5.5's gethostname whereby it NUL-terminates HOSTNAME
          even when the name is as long as the supplied buffer.  */
-      size_t size_1;
-
-      hostname = x2realloc (hostname, &size);
-      size_1 = size - 1;
-      hostname[size_1 - 1] = '\0';
+      idx_t size_1 = size - 1;
+      name[size_1] = '\0';
       errno = 0;
-
-      if (gethostname (hostname, size_1) == 0)
+      if (GETANAME (name, size_1) == 0)
         {
-          if (! hostname[size_1 - 1])
-            break;
-        }
-      else if (errno != 0 && errno != ENAMETOOLONG && errno != EINVAL
-               /* OSX/Darwin does this when the buffer is not large enough */
-               && errno != ENOMEM)
-        {
-          free (hostname);
-          return NULL;
+          /* Check whether the name was possibly truncated; POSIX does not
+             specify whether a truncated name is null-terminated.  */
+          idx_t actual_size = strlen (name) + 1;
+          if (actual_size < size_1)
+            return alloc ? alloc : xmemdup (name, actual_size);
+          errno = 0;
         }
+      free (alloc);
+      if (errno != 0 && errno != ENAMETOOLONG && errno != EINVAL
+          /* macOS/Darwin does this when SIZE_1 is too small.  */
+          && errno != ENOMEM)
+        return NULL;
+      name = alloc = xpalloc (NULL, &size, 1, -1, 1);
     }
-
-  /* Shrink HOSTNAME before returning it.  */
-  {
-    size_t actual_size = strlen (hostname) + 1;
-    if (actual_size < size)
-      {
-        char *shrinked_hostname = realloc (hostname, actual_size);
-        if (shrinked_hostname != NULL)
-          hostname = shrinked_hostname;
-      }
-  }
-
-  return hostname;
 }
diff --git a/modules/xgetdomainname b/modules/xgetdomainname
index d1c9f2459..c1417c8ef 100644
--- a/modules/xgetdomainname
+++ b/modules/xgetdomainname
@@ -6,9 +6,8 @@ lib/xgetdomainname.h
 lib/xgetdomainname.c
 
 Depends-on:
-free-posix
 getdomainname
-xalloc
+xgethostname
 
 configure.ac:
 
-- 
2.27.0

Re: remove xgetdomainname module from Gnulib?

[Simon Josefsson via Gnulib discussion list]

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Paul Eggert <eggert@cs.ucla.edu> writes:

> On 4/2/21 8:32 AM, Paul Eggert wrote:
>> I can fix it by removing the divergence.
>
> I did that by installing the attached, which causes xgetdomainname.c
> to be a couple of #defines followed by "#include "xgethostname.c".

Thank you!

/Simon

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