Re: HAVE_STDBOOL_H, AC_HEADER_STDBOOL, and AM_STDBOOL_H

[Paul Eggert]

On 02/01/2011 07:58 AM, Eric Blake wrote:
> I agree 100% that the two macros must be split and that gnulib should
> not use AC_HEADER_STDBOOL, but I don't (yet) see any convincing reason
> either for or against marking the autoconf macro obsolete

OK, thanks, I installed the following patches to autoconf and to gnulib,
respectively.  It implements this more-conservative suggestion.

>From 81b5c5b9fafdcf0b6ba51728ff76d679d35ece13 Mon Sep 17 00:00:00 2001
From: Paul Eggert <address@hidden>
Date: Fri, 4 Feb 2011 20:38:07 -0800
Subject: [PATCH] autoconf: new macro AC_HEADER_CHECK_STDBOOL

* NEWS: Document this.
* doc/autoconf.texi (Particular Headers): Likewise.
In example, don't assume a 'system.h' exists.
* lib/autoconf/headers.m4 (AC_CHECK_HEADER_STDBOOL): New macro.
Use it with AN_IDENTIFIER, since it's less heavyweight.
Reindent to match gnulib, since that's a bit nicer.
(AC_HEADER_STDBOOL): Reimplement in terms of it.
---
 ChangeLog               |   11 ++++
 NEWS                    |    3 +
 doc/autoconf.texi       |   33 +++++++++--
 lib/autoconf/headers.m4 |  135 +++++++++++++++++++++++++----------------------
 4 files changed, 113 insertions(+), 69 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index b36aab1..6d65401 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,14 @@
+2011-02-04  Paul Eggert  <address@hidden>
+
+       autoconf: new macro AC_HEADER_CHECK_STDBOOL
+       * NEWS: Document this.
+       * doc/autoconf.texi (Particular Headers): Likewise.
+       In example, don't assume a 'system.h' exists.
+       * lib/autoconf/headers.m4 (AC_CHECK_HEADER_STDBOOL): New macro.
+       Use it with AN_IDENTIFIER, since it's less heavyweight.
+       Reindent to match gnulib, since that's a bit nicer.
+       (AC_HEADER_STDBOOL): Reimplement in terms of it.
+
 2011-01-29  Jim Warhol  <address@hidden>  (tiny change)
 
        * doc/autoconf.texi (Introduction): Fix typo.
diff --git a/NEWS b/NEWS
index d00c312..c485f22 100644
--- a/NEWS
+++ b/NEWS
@@ -5,6 +5,9 @@ GNU Autoconf NEWS - User visible changes.
 ** AS_LITERAL_IF again treats '=' as a literal.  Regression introduced in
    2.66.
 
+** Macros
+
+- New macro AC_HEADER_CHECK_STDBOOL.
 
 * Noteworthy changes in release 2.68 (2010-09-22) [stable]
   Released by Eric Blake, based on git versions 2.67.*.
diff --git a/doc/autoconf.texi b/doc/autoconf.texi
index b1ccb1a..6ad657e 100644
--- a/doc/autoconf.texi
+++ b/doc/autoconf.texi
@@ -5811,6 +5811,21 @@ AC_CHECK_HEADERS([X11/extensions/scrnsaver.h], [], [],
 These macros check for particular system header files---whether they
 exist, and in some cases whether they declare certain symbols.
 
address@hidden AC_CHECK_HEADER_STDBOOL
address@hidden
address@hidden HAVE__BOOL
address@hidden
address@hidden header_stdbool_h
+Check whether @file{stdbool.h} exists and conforms to C99, and cache the
+result in the @code{ac_cv_header_stdbool_h} variable.  If the type
address@hidden is defined, define @code{HAVE__BOOL} to 1.
+
+This macro is intended for use by Gnulib (@pxref{Gnulib}) and other
+packages that supply a substitute @file{stdbool.h} on platforms lacking
+a conforming one.  The @code{AC_HEADER_STDBOOL} macro is better for code
+that explicitly checks for @file{stdbool.h}.
address@hidden defmac
+
 @defmac AC_HEADER_ASSERT
 @acindex{HEADER_ASSERT}
 @cvindex NDEBUG
@@ -5937,14 +5952,14 @@ New programs need not use this macro.
 @cvindex HAVE_STDBOOL_H
 @cvindex HAVE__BOOL
 @hdrindex{stdbool.h}
address@hidden
 @caindex header_stdbool_h
 If @file{stdbool.h} exists and conforms to C99, define
 @code{HAVE_STDBOOL_H} to 1; if the type @code{_Bool} is defined, define
 @code{HAVE__BOOL} to 1.  To fulfill the C99 requirements, your
address@hidden could contain the following code:
+program could contain the following code:
 
address@hidden
address@hidden
address@hidden
 #ifdef HAVE_STDBOOL_H
 # include <stdbool.h>
 #else
@@ -5960,14 +5975,20 @@ typedef bool _Bool;
 # define true 1
 # define __bool_true_false_are_defined 1
 #endif
address@hidden verbatim
address@hidden group
address@hidden example
 
 Alternatively you can use the @samp{stdbool} package of Gnulib
-(@pxref{Gnulib}); it packages the above code into a replacement header
-and contains a few other bells and whistles.
+(@pxref{Gnulib}).  It simplifies your code so that it can say just
address@hidden <stdbool.h>}, and it adds support for less-common
+platforms.
 
 This macro caches its result in the @code{ac_cv_header_stdbool_h}
 variable.
+
+This macro differs from @code{AC_CHECK_HEADER_STDBOOL} only in that it
+defines @code{HAVE_STDBOOL_H} whereas @code{AC_CHECK_HEADER_STDBOOL}
+does not.
 @end defmac
 
 @anchor{AC_HEADER_STDC}
diff --git a/lib/autoconf/headers.m4 b/lib/autoconf/headers.m4
index 75bdfef..4b02832 100644
--- a/lib/autoconf/headers.m4
+++ b/lib/autoconf/headers.m4
@@ -591,72 +591,81 @@ fi
 ])# AC_HEADER_STAT
 
 
-# AC_HEADER_STDBOOL
+# AC_CHECK_HEADER_STDBOOL
 # -----------------
 # Check for stdbool.h that conforms to C99.
-AN_IDENTIFIER([bool], [AC_HEADER_STDBOOL])
-AN_IDENTIFIER([true], [AC_HEADER_STDBOOL])
-AN_IDENTIFIER([false],[AC_HEADER_STDBOOL])
-AC_DEFUN([AC_HEADER_STDBOOL],
-[AC_CACHE_CHECK([for stdbool.h that conforms to C99],
-   [ac_cv_header_stdbool_h],
-   [AC_COMPILE_IFELSE([AC_LANG_PROGRAM(
-      [[
-#include <stdbool.h>
-#ifndef bool
- "error: bool is not defined"
-#endif
-#ifndef false
- "error: false is not defined"
-#endif
-#if false
- "error: false is not 0"
-#endif
-#ifndef true
- "error: true is not defined"
-#endif
-#if true != 1
- "error: true is not 1"
-#endif
-#ifndef __bool_true_false_are_defined
- "error: __bool_true_false_are_defined is not defined"
-#endif
+AN_IDENTIFIER([bool], [AC_CHECK_HEADER_STDBOOL])
+AN_IDENTIFIER([true], [AC_CHECK_HEADER_STDBOOL])
+AN_IDENTIFIER([false],[AC_CHECK_HEADER_STDBOOL])
+AC_DEFUN([AC_CHECK_HEADER_STDBOOL],
+  [AC_CACHE_CHECK([for stdbool.h that conforms to C99],
+     [ac_cv_header_stdbool_h],
+     [AC_COMPILE_IFELSE(
+        [AC_LANG_PROGRAM(
+           [[
+             #include <stdbool.h>
+             #ifndef bool
+              "error: bool is not defined"
+             #endif
+             #ifndef false
+              "error: false is not defined"
+             #endif
+             #if false
+              "error: false is not 0"
+             #endif
+             #ifndef true
+              "error: true is not defined"
+             #endif
+             #if true != 1
+              "error: true is not 1"
+             #endif
+             #ifndef __bool_true_false_are_defined
+              "error: __bool_true_false_are_defined is not defined"
+             #endif
+
+             struct s { _Bool s: 1; _Bool t; } s;
+
+             char a[true == 1 ? 1 : -1];
+             char b[false == 0 ? 1 : -1];
+             char c[__bool_true_false_are_defined == 1 ? 1 : -1];
+             char d[(bool) 0.5 == true ? 1 : -1];
+             /* See body of main program for 'e'.  */
+             char f[(_Bool) 0.0 == false ? 1 : -1];
+             char g[true];
+             char h[sizeof (_Bool)];
+             char i[sizeof s.t];
+             enum { j = false, k = true, l = false * true, m = true * 256 };
+             /* The following fails for
+                HP aC++/ANSI C B3910B A.05.55 [Dec 04 2003]. */
+             _Bool n[m];
+             char o[sizeof n == m * sizeof n[0] ? 1 : -1];
+             char p[-1 - (_Bool) 0 < 0 && -1 - (bool) 0 < 0 ? 1 : -1];
+             /* Catch a bug in an HP-UX C compiler.  See
+                http://gcc.gnu.org/ml/gcc-patches/2003-12/msg02303.html
+                
http://lists.gnu.org/archive/html/bug-coreutils/2005-11/msg00161.html
+              */
+             _Bool q = true;
+             _Bool *pq = &q;
+           ]],
+           [[
+             bool e = &s;
+             *pq |= q;
+             *pq |= ! q;
+             /* Refer to every declared value, to avoid compiler 
optimizations.  */
+             return (!a + !b + !c + !d + !e + !f + !g + !h + !i + !!j + !k + 
!!l
+                     + !m + !n + !o + !p + !q + !pq);
+           ]])],
+        [ac_cv_header_stdbool_h=yes],
+        [ac_cv_header_stdbool_h=no])])
+   AC_CHECK_TYPES([_Bool])
+])# AC_CHECK_HEADER_STDBOOL
+
 
-       struct s { _Bool s: 1; _Bool t; } s;
-
-       char a[true == 1 ? 1 : -1];
-       char b[false == 0 ? 1 : -1];
-       char c[__bool_true_false_are_defined == 1 ? 1 : -1];
-       char d[(bool) 0.5 == true ? 1 : -1];
-       /* See body of main program for 'e'.  */
-       char f[(_Bool) 0.0 == false ? 1 : -1];
-       char g[true];
-       char h[sizeof (_Bool)];
-       char i[sizeof s.t];
-       enum { j = false, k = true, l = false * true, m = true * 256 };
-       /* The following fails for
-          HP aC++/ANSI C B3910B A.05.55 [Dec 04 2003]. */
-       _Bool n[m];
-       char o[sizeof n == m * sizeof n[0] ? 1 : -1];
-       char p[-1 - (_Bool) 0 < 0 && -1 - (bool) 0 < 0 ? 1 : -1];
-       /* Catch a bug in an HP-UX C compiler.  See
-          http://gcc.gnu.org/ml/gcc-patches/2003-12/msg02303.html
-          http://lists.gnu.org/archive/html/bug-coreutils/2005-11/msg00161.html
-        */
-       _Bool q = true;
-       _Bool *pq = &q;
-      ]],
-      [[
-       bool e = &s;
-       *pq |= q;
-       *pq |= ! q;
-       /* Refer to every declared value, to avoid compiler optimizations.  */
-       return (!a + !b + !c + !d + !e + !f + !g + !h + !i + !!j + !k + !!l
-               + !m + !n + !o + !p + !q + !pq);
-      ]])],
-      [ac_cv_header_stdbool_h=yes],
-      [ac_cv_header_stdbool_h=no])])
-AC_CHECK_TYPES([_Bool])
+# AC_HEADER_STDBOOL
+# -----------------
+# Define HAVE_STDBOOL_H if tdbool.h that conforms to C99.
+AC_DEFUN([AC_HEADER_STDBOOL],
+[AC_CHECK_HEADER_STDBOOL
 if test $ac_cv_header_stdbool_h = yes; then
   AC_DEFINE(HAVE_STDBOOL_H, 1, [Define to 1 if stdbool.h conforms to C99.])
 fi
-- 
1.7.4

>From f0f4bea6c4efd2b5a1e058beb7dce5a9342647cd Mon Sep 17 00:00:00 2001
From: Paul Eggert <address@hidden>
Date: Fri, 4 Feb 2011 20:54:58 -0800
Subject: [PATCH] stdbool: do not define HAVE_STDBOOL_H

* m4/stdbool.m4 (AC_CHECK_HEADER_STDBOOL): Renamed from
AC_HEADER_STDBOOL.  All uses changed.  Do not define
HAVE_STDBOOL_H, as gnulib does not need this.  This change is
imported from the latest Autoconf git.  It was motivated by Emacs,
which uses gnulib but does not need HAVE_STDBOOL_H.
---
 ChangeLog     |    9 +++++++++
 m4/stdbool.m4 |   14 +++++---------
 2 files changed, 14 insertions(+), 9 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index f2e20c1..fd79da1 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+2011-02-04  Paul Eggert  <address@hidden>
+
+       stdbool: do not define HAVE_STDBOOL_H
+       * m4/stdbool.m4 (AC_CHECK_HEADER_STDBOOL): Renamed from
+       AC_HEADER_STDBOOL.  All uses changed.  Do not define
+       HAVE_STDBOOL_H, as gnulib does not need this.  This change is
+       imported from the latest Autoconf git.  It was motivated by Emacs,
+       which uses gnulib but does not need HAVE_STDBOOL_H.
+
 2011-02-04  Bruno Haible  <address@hidden>
 
        wcsnrtombs: Prepare for new module wwcsnrtombs.
diff --git a/m4/stdbool.m4 b/m4/stdbool.m4
index df10486..838cf0f 100644
--- a/m4/stdbool.m4
+++ b/m4/stdbool.m4
@@ -5,13 +5,13 @@ 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.
 
-#serial 3
+#serial 4
 
 # Prepare for substituting <stdbool.h> if it is not supported.
 
 AC_DEFUN([AM_STDBOOL_H],
 [
-  AC_REQUIRE([AC_HEADER_STDBOOL])
+  AC_REQUIRE([AC_CHECK_HEADER_STDBOOL])
 
   # Define two additional variables used in the Makefile substitution.
 
@@ -33,11 +33,9 @@ AC_DEFUN([AM_STDBOOL_H],
 # AM_STDBOOL_H will be renamed to gl_STDBOOL_H in the future.
 AC_DEFUN([gl_STDBOOL_H], [AM_STDBOOL_H])
 
-# This version of the macro is needed in autoconf <= 2.67.  Autoconf has
-# it built in since 2.60, but we want the tweaks from the 2.68 version
-# to avoid rejecting xlc and clang due to relying on extensions.
+# This version of the macro is needed in autoconf <= 2.68.
 
-AC_DEFUN([AC_HEADER_STDBOOL],
+AC_DEFUN([AC_CHECK_HEADER_STDBOOL],
   [AC_CACHE_CHECK([for stdbool.h that conforms to C99],
      [ac_cv_header_stdbool_h],
      [AC_COMPILE_IFELSE(
@@ -98,6 +96,4 @@ AC_DEFUN([AC_HEADER_STDBOOL],
         [ac_cv_header_stdbool_h=yes],
         [ac_cv_header_stdbool_h=no])])
    AC_CHECK_TYPES([_Bool])
-   if test $ac_cv_header_stdbool_h = yes; then
-     AC_DEFINE([HAVE_STDBOOL_H], [1], [Define to 1 if stdbool.h conforms to 
C99.])
-   fi])
+])
-- 
1.7.4