Re: Checking automatically for default headers

[Pavel Roskin]

Hello, Akim!

On 15 Jan 2001, Akim Demaille wrote:

> A suggestion from Jim: as soon as default includes are used, let's
> look for the headers which correspond.  And, BTW, let's not include
> the definition of the default headers when they are not used (see the
> changes of Autoconf's own configure).

The idea is good.

> -# By default always use an empty string as the executable extension.
> -# Only change it if the script calls AC_EXEEXT.
> -ac_exeext=
> -# By default assume that objects files use an extension of .o.  Only
> -# change it if the script calls AC_OBJEXT.
> -ac_objext=o

You are removing it here, but I don't understand how it corresponds with
the description of the patch, and why those assignments don't appear
anywhere else.

> -# Of course, one would like to issue these default headers only if
> -# they were used, i.e.., AC_INCLUDES_DEFAULT was called, and the
> -# default `branch' was run.  Unfortunately AC_INCLUDES_DEFAULT is
> -# called unquoted, so it is unsafe to try to divert from there.
> -# Therefore, the following *is* buggy, but this is the kind of
> -# tradeoff we accept in order to improve configure.

This sounds scary, and I don't understand why you are removing this
comment. Probably you have found a solution?

> -m4_define([AC_INCLUDES_DEFAULT],
> +AC_DEFUN([AC_INCLUDES_DEFAULT],

In fact, we need a very clear indication around those line that the macro
is meant to be used unquoted, so that nobody adds e.g. a comma without
being unaware of the consequences,

> Index: configure
> ===================================================================
> RCS file: /cvs/autoconf/configure,v

Akim, "cvs diff" is not something I would rely upon. You need a script for
your needs that would exclude dependent files (Makefile.in, configure),
something around the lines of my ldiff, but with improved "find"
command:

http://www.red-bean.com/~proski/ldiff/

> diff -u -u -r1.14 semantics.at
> --- tests/semantics.at 2001/01/11 15:17:13 1.14
> +++ tests/semantics.at 2001/01/15 17:02:06
> @@ -103,7 +103,13 @@
>  typedef unsigned char ucharchar[2];]])
>  AC_CHECK_SIZEOF(ucharcharchar)]],
>  [AT_CHECK_DEFINES(
> -[#define SIZEOF_CHAR 1
> +[#define HAVE_INTTYPES_H 1

"There You Go Again, Mr. Reagan" - Walter F. Mondale.

We just fixed that bug. Linux libc-5 doesn't have inttypes.h

Regards,
Pavel Roskin