Re: how to prefix definitions in config.h

[Guido Draheim]

ac_create_prefix_config_h does not only prefix the names, they get
also converted into ifdefs. That was also necessary, since I had
some problems as this prefixed-header might be included multiple
times, as there is not ifdef-once header/footer for the file
itself. That's my solution to the problem, for making the checks
of autoconf available via a generated header that gets defined
through ac_define's. -- guido



Es schrieb Russ Allbery:
> 
> Guido Draheim <address@hidden> writes:
> 
> > I'm doing the same thing, and in fact, all libraries should put their
> > headers with a subdir prefix, sadly not all of them do it, and
> > automake's support for such a style is limited. Anyway, two ways.
> 
> > a) I'm using package/_config.h - this even hint the reader that this
> >    file is not a normal header (it is generated!) and it does not
> >    get confused for the standard config.h file.
> > b) look at the argument of AC_CONFIG_HEADER - you can specify a
> >    different output-file, so that you don't need to have the two
> >    same-named.
> 
> The name isn't the problem.
> 
> Suppose that you have two installable libraries that use autoconf, and in
> both of those libraries you need to probe for a few system features, like
> the proper types, and change the headers and prototypes based on that.
> Now suppose you want to write a program that uses both of those libraries.
> If you include both header files, then the separate package config.h files
> will potentially conflict with each other and result in a bunch of
> redefinition errors.
> 
> One thing that you can do is recognize that generally your interface only
> depends on a much restricted subset of the things that you probe for
> actual compilation, and therefore you only need to install a stripped down
> version of config.h.  For INN, I use the following awk script to generate
> that stripped-down version with only the symbols that the header files
> need to use, and just add new symbols to it as I need them for the API:
> 
> #! /bin/sh
> 
> ##  $Id: mksystem,v 1.1 2001/02/24 07:59:06 rra Exp $
> ##
> ##  Create include/inn/system.h from include/config.h.
> ##
> ##  include/config.h is generated by autoconf and contains all of the test
> ##  results for a platform.  Most of these are only used when building INN,
> ##  but some of them are needed for various definitions in the header files
> ##  for INN's libraries.  We want to be able to install those header files
> ##  and their prerequisites, but we don't want to define the normal symbols
> ##  defined by autoconf since they're too likely to conflict with other
> ##  packages.
> ##
> ##  This script takes the path to include/config.h as its only argument and
> ##  generates a file suitable for being included as <inn/system.h>.  It
> ##  contains only the autoconf results needed for INN's API, and the symbols
> ##  that might conflict with autoconf results in other packages have INN_
> ##  prepended.
> 
> cat <<EOF
> /* Automatically generated by mksystem from config.h; do not edit. */
> 
> /* This header contains information obtained by INN at configure time that
>    is needed by INN headers.  Autoconf results that may conflict with the
>    autoconf results of another package have INN_ prepended to the
>    preprocessor symbols. */
> 
> #ifndef INN_SYSTEM_H
> #define INN_SYSTEM_H 1
> 
> EOF
> 
> awk -f - $1 <<'---END-OF-AWK-SCRIPT---'
> 
> /^#define HAVE_INTTYPES_H/      { print save $1 " INN_" $2 " " $3 "\n" }
> /^#define HAVE_STDBOOL_H/       { print save $1 " INN_" $2 " " $3 "\n" }
> /^#define HAVE_SYS_BITTYPES_H/  { print save $1 " INN_" $2 " " $3 "\n" }
> 
> { save = $0 "\n" }
> 
> ---END-OF-AWK-SCRIPT---
> 
> cat <<EOF
> #endif /* INN_SYSTEM_H */
> EOF
> 
> --
> Russ Allbery (address@hidden)             <http://www.eyrie.org/~eagle/>