>>>>> "Peter" == Peter Eisentraut <[EMAIL PROTECTED]> writes:
Peter> Akim Demaille writes:
>> I know what you are going to say: we don't need autoheader, we
>> should just spit a cleaned up version of confdefs.h, as your patch
>> does. But I don't share this opinion, so yes, it is important to
>> run autoheader.
Peter> Just for my enlightenment: Why is it actually important to run
Peter> autoheader before configure, rather than just having configure
Peter> do that job?
See the patch in the queue :)
| Index: ChangeLog
| from Akim Demaille <[EMAIL PROTECTED]>
| * doc/autoconf.texi (autoheader Invocation): Explain the purpose
| of autoheader.
|
|
| Index: doc/autoconf.texi
| --- 0.420/doc/autoconf.texi Mon, 17 Jul 2000 21:25:15 +0200 akim (ace/16_autoconf.t
|1.61.2.66 644)
| +++ 0.420(w)/doc/autoconf.texi Mon, 17 Jul 2000 21:44:15 +0200 akim
|(ace/16_autoconf.t 1.61.2.66 644)
| @@ -1982,16 +1982,44 @@ @node autoheader Invocation, Autoheader
| @subsection Using @code{autoheader} to Create @file{config.h.in}
| @cindex @code{autoheader}
|
| -The @code{autoheader} program can create a template file of C
| +The @command{autoheader} program can create a template file of C
| @samp{#define} statements for @code{configure} to use. If
| @file{configure.in} invokes @code{AC_CONFIG_HEADERS(@var{file})},
| -@code{autoheader} creates @file{@var{file}.in}; if multiple file
| +@command{autoheader} creates @file{@var{file}.in}; if multiple file
| arguments are given, the first one is used. Otherwise,
| -@code{autoheader} creates @file{config.h.in}.
| +@command{autoheader} creates @file{config.h.in}.
|
| -If you give @code{autoheader} an argument, it uses that file instead of
| -@file{configure.in} and writes the header file to the standard output
| -instead of to @file{config.h.in}. If you give @code{autoheader} an
| +In order to do its job @command{autoheader} needs that you document all
| +the symbols that you might use, i.e., that there is at least one
| +@code{AC_DEFINE} or one @code{AC_DEFINE_UNQUOTED} using its third
| +argument, see @ref{Defining Symbols}. An additional constraint is that
| +the first argument must be a literal.
| +
| +You might wonder why @command{autoheader} is needed: after all, why
| +would @command{configure} need to ``patch'' a @file{config.h.in} to
| +produce a @file{config.h} instead of just creating @file{config.h} from
| +scratch?
| +
| +Well, when everything rocks the answer is just that we are losing our
| +time maintaining @command{autoheader}: generating directly
| +@file{config.h} is just what is needed.
| +
| +But when things go wrong, you'll thanks the Autoconf team for
| +@command{autoheader}...
| +
| +The fact that the symbols are documented is precious to @emph{check}
| +that @file{config.h} makes sense.
| +
| +The fact that there is a well defined list of symbols which should be
| +@code{#define}'d (or not) is also precious for people who are porting
| +packages to environments where @command{configure} cannot be run: they
| +just have to @emph{fill in the blanks}.
| +
| +But let's come back to the point: @command{autoheader}'s invocation...
| +
| +If you give @command{autoheader} an argument, it uses that file instead
| +of @file{configure.in} and writes the header file to the standard output
| +instead of to @file{config.h.in}. If you give @command{autoheader} an
| argument of @option{-}, it reads the standard input instead of
| @file{configure.in} and writes the header file to the standard output.
|
| @@ -6766,7 +6794,7 @@ @node Coding Style, , Obsoleting Macros
| not escape when it is unneeded. Common examples of useless quotation
| are @samp{[$]$1} (write @samp{$$1}), @samp{[$]var} (use @samp{$var}),
| etc. If you add portability issues to the picture, you'll prefer
| -@samp{${1+"$[@@]"}} to @samp{"[$]@@"}, and you'll prefer do something
| +@samp{$@{1+"$[@@]"@}} to @samp{"[$]@@"}, and you'll prefer do something
| better than hacking Autoconf @code{:-)}.
|
| When using @command{sed}, don't use @option{-e} but for indenting
Yes, it is a constraint to live with autoheader, but I think it is a
sane constraint.
In addition, I never saw any real life example where autoheader proves
to be a true limitations.
Something else I have not said in the documentation above is that this
(patching a template instead of mv confdefs.h config.h) allows you to
select which are the symbols which will be expanded. Some people seem
to rely on such things.
Akim
