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Under GNU General Public License
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File: autoconf.info, Node: autoheader Invocation, Next: Autoheader Macros, Prev: Header Templates, Up: Configuration Headers
4.9.2 Using `autoheader' to Create `config.h.in'
------------------------------------------------
The `autoheader' program can create a template file of C `#define'
statements for `configure' to use. It searches for the first
invocation of `AC_CONFIG_HEADERS' in `configure' sources to determine
the name of the template. (If the first call of `AC_CONFIG_HEADERS'
specifies more than one input file name, `autoheader' uses the first
one.)
It is recommended that only one input file is used. If you want to
append a boilerplate code, it is preferable to use `AH_BOTTOM([#include
<conf_post.h>])'. File `conf_post.h' is not processed during the
configuration then, which make things clearer. Analogically, `AH_TOP'
can be used to prepend a boilerplate code.
In order to do its job, `autoheader' needs you to document all of
the symbols that you might use. Typically this is done via an
`AC_DEFINE' or `AC_DEFINE_UNQUOTED' call whose first argument is a
literal symbol and whose third argument describes the symbol (*note
Defining Symbols::). Alternatively, you can use `AH_TEMPLATE' (*note
Autoheader Macros::), or you can supply a suitable input file for a
subsequent configuration header file. Symbols defined by Autoconf's
builtin tests are already documented properly; you need to document
only those that you define yourself.
You might wonder why `autoheader' is needed: after all, why would
`configure' need to "patch" a `config.h.in' to produce a `config.h'
instead of just creating `config.h' from scratch? Well, when
everything rocks, the answer is just that we are wasting our time
maintaining `autoheader': generating `config.h' directly is all that is
needed. When things go wrong, however, you'll be thankful for the
existence of `autoheader'.
The fact that the symbols are documented is important in order to
_check_ that `config.h' makes sense. The fact that there is a
well-defined list of symbols that should be defined (or not) is also
important for people who are porting packages to environments where
`configure' cannot be run: they just have to _fill in the blanks_.
But let's come back to the point: the invocation of `autoheader'...
If you give `autoheader' an argument, it uses that file instead of
`configure.ac' and writes the header file to the standard output
instead of to `config.h.in'. If you give `autoheader' an argument of
`-', it reads the standard input instead of `configure.ac' and writes
the header file to the standard output.
`autoheader' accepts the following options:
`--help'
`-h'
Print a summary of the command line options and exit.
`--version'
`-V'
Print the version number of Autoconf and exit.
`--verbose'
`-v'
Report processing steps.
`--debug'
`-d'
Don't remove the temporary files.
`--force'
`-f'
Remake the template file even if newer than its input files.
`--include=DIR'
`-I DIR'
Append DIR to the include path. Multiple invocations accumulate.
`--prepend-include=DIR'
`-B DIR'
Prepend DIR to the include path. Multiple invocations accumulate.
`--warnings=CATEGORY'
`-W CATEGORY'
Report the warnings related to CATEGORY (which can actually be a
comma separated list). Current categories include:
`obsolete'
report the uses of obsolete constructs
`all'
report all the warnings
`none'
report none
`error'
treats warnings as errors
`no-CATEGORY'
disable warnings falling into CATEGORY
Generated by $Id: phpMan.php,v 4.55 2007/09/05 04:42:51 chedong Exp $ Author: Che Dong
On Apache
Under GNU General Public License
2024-04-19 04:40 @18.224.149.242 CrawledBy Mozilla/5.0 AppleWebKit/537.36 (KHTML, like Gecko; compatible; ClaudeBot/1.0; +claudebot@anthropic.com)