Re: HOST_NAME_MAX

[Bruno Haible]

Simon Josefsson wrote on 2009-04-01:
> > The definition can be triggered by the 'gethostname' module. I don't think
> > anyone will need HOST_NAME_MAX without needing the gethostname() function.
> 
> That would be fine with me.  How about the patch below?  This is on top
> of my earlier gethostname patch for mingw.
> 
> /Simon
> 
> diff --git a/doc/posix-headers/limits.texi b/doc/posix-headers/limits.texi
> index 0b5e431..d404b9c 100644
> --- a/doc/posix-headers/limits.texi
> +++ b/doc/posix-headers/limits.texi
> @@ -11,4 +11,7 @@ Portability problems fixed by Gnulib:
>  
>  Portability problems not fixed by Gnulib:
>  @itemize
> +The @code{HOST_NAME_MAX} symbol is not defined under Windows, use the
> address@hidden gnulib module to get it.
> +
>  @end itemize
> diff --git a/m4/gethostname.m4 b/m4/gethostname.m4
> index 620e023..a2b8e60 100644
> --- a/m4/gethostname.m4
> +++ b/m4/gethostname.m4
> @@ -42,7 +42,13 @@ AC_DEFUN([gl_FUNC_GETHOSTNAME],
>  
>  # Prerequisites of lib/gethostname.c.
>  AC_DEFUN([gl_PREREQ_GETHOSTNAME], [
> -  if test "$gl_cv_w32_gethostname" != "yes"; then
> +  if test "$gl_cv_w32_gethostname" = "yes"; then
> +    # <http://msdn.microsoft.com/en-us/library/ms738527.aspx> says:
> +    # "if a buffer of 256 bytes is passed in the name parameter and
> +    # the namelen parameter is set to 256, the buffer size will always
> +    # be adequate."
> +    AC_DEFINE([HOST_NAME_MAX], [256], [Define HOST_NAME_MAX on Mingw.])
> +  else
>      AC_CHECK_FUNCS([uname])
>    fi
>  ])
> diff --git a/modules/gethostname b/modules/gethostname
> index e21afe6..a50c22b 100644
> --- a/modules/gethostname
> +++ b/modules/gethostname
> @@ -1,5 +1,5 @@
>  Description:
> -gethostname() function: Return machine's hostname.
> +Provide HOST_NAME_MAX and gethostname() function: Return machine's hostname.
>  
>  Files:
>  lib/gethostname.c
> diff --git a/tests/test-gethostname.c b/tests/test-gethostname.c
> index ef50953..c1914fd 100644
> --- a/tests/test-gethostname.c
> +++ b/tests/test-gethostname.c
> @@ -1,5 +1,5 @@
>  /*
> - * Copyright (C) 2008 Free Software Foundation
> + * Copyright (C) 2008, 2009 Free Software Foundation
>   * Written by Simon Josefsson.
>   *
>   * This program is free software: you can redistribute it and/or modify
> @@ -28,9 +28,15 @@
>  int
>  main (int argc, char *argv[])
>  {
> -  char buf[2500];
> +  char buf[HOST_NAME_MAX];
>    int rc;
>  
> +  if (strlen (NOHOSTNAME) >= HOST_NAME_MAX)
> +    {
> +      printf ("HOST_NAME_MAX impossibly small?! %d\n", HOST_NAME_MAX);
> +      return 2;
> +    }
> +
>    strcpy (buf, NOHOSTNAME);
>  
>    rc = gethostname (buf, sizeof (buf));
> 
> 

I've applied it with a few tweaks, as follows:
  - Document the problem under "problems fixed by Gnulib", not under
    "problems not fixed by Gnulib".
  - Move the AC_DEFINE out of gl_PREREQ_GETHOSTNAME, since it's the
    user who wants HOST_NAME_MAX; the code in lib/gethostname.c does
    not need it.


2009-08-02  Simon Josefsson  <address@hidden>
            Bruno Haible  <address@hidden>

        Ensure HOST_NAME_MAX as part of the gethostname module.
        * m4/gethostname.m4 (gl_FUNC_GETHOSTNAME): On native Windows platforms,
        define also HOST_NAME_MAX.
        * tests/test-gethostname.c (main): Check also HOST_NAME_MAX.
        * doc/posix-headers/limits.texi: Document the mingw problem.

--- doc/posix-headers/limits.texi.orig  2009-08-02 12:23:35.000000000 +0200
+++ doc/posix-headers/limits.texi       2009-08-02 12:19:39.000000000 +0200
@@ -3,10 +3,12 @@
 
 POSIX specification: @url{http://www.opengroup.org/susv3xbd/limits.h.html}
 
-Gnulib module: ---
+Gnulib module: gethostname
 
 Portability problems fixed by Gnulib:
 @itemize
+The @code{HOST_NAME_MAX} macro is not defined on some platforms:
+mingw.
 @end itemize
 
 Portability problems not fixed by Gnulib:
--- m4/gethostname.m4.orig      2009-08-02 12:23:35.000000000 +0200
+++ m4/gethostname.m4   2009-08-02 12:23:30.000000000 +0200
@@ -1,9 +1,12 @@
-# gethostname.m4 serial 6
+# gethostname.m4 serial 7
 dnl Copyright (C) 2002, 2008, 2009 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
 dnl with or without modifications, as long as this notice is preserved.
 
+# Ensure
+# - the gethostname() function,
+# - the HOST_NAME_MAX macro in <limits.h>.
 AC_DEFUN([gl_FUNC_GETHOSTNAME],
 [
   AC_REQUIRE([gl_UNISTD_H_DEFAULTS])
@@ -38,6 +41,16 @@
     HAVE_GETHOSTNAME=0
     gl_PREREQ_GETHOSTNAME
   fi
+
+  dnl Also provide HOST_NAME_MAX when <limits.h> lacks it.
+  if test "$gl_cv_w32_gethostname" = "yes"; then
+    # <http://msdn.microsoft.com/en-us/library/ms738527.aspx> says:
+    # "if a buffer of 256 bytes is passed in the name parameter and
+    # the namelen parameter is set to 256, the buffer size will always
+    # be adequate."
+    AC_DEFINE([HOST_NAME_MAX], [256],
+      [Define HOST_NAME_MAX when <limits.h> does not define it.])
+  fi
 ])
 
 # Prerequisites of lib/gethostname.c.
--- tests/test-gethostname.c.orig       2009-08-02 12:23:35.000000000 +0200
+++ tests/test-gethostname.c    2009-08-02 12:13:57.000000000 +0200
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2008 Free Software Foundation
+ * Copyright (C) 2008, 2009 Free Software Foundation
  * Written by Simon Josefsson.
  *
  * This program is free software: you can redistribute it and/or modify
@@ -28,9 +28,15 @@
 int
 main (int argc, char *argv[])
 {
-  char buf[2500];
+  char buf[HOST_NAME_MAX];
   int rc;
 
+  if (strlen (NOHOSTNAME) >= HOST_NAME_MAX)
+    {
+      printf ("HOST_NAME_MAX impossibly small?! %d\n", HOST_NAME_MAX);
+      return 2;
+    }
+
   strcpy (buf, NOHOSTNAME);
 
   rc = gethostname (buf, sizeof (buf));