autoconf.info: autoheader Invocation
Go forward to Autoheader Macros
Go backward to Header Templates
Go up to Configuration Headers
Go to the top op autoconf
Using `autoheader' to Create `config.h.in'
The `autoheader' program can create a template file of C `#define'
statements for `configure' to use. If `configure.ac' invokes
`AC_CONFIG_HEADERS(FILE)', `autoheader' creates `FILE.in'; if multiple
file arguments are given, the first one is used. Otherwise,
`autoheader' creates `config.h.in'.
In order to do its job, `autoheader' needs you to document all of
the symbols that you might use; i.e., there must be at least one
`AC_DEFINE' or one `AC_DEFINE_UNQUOTED' call with a third argument for
each symbol (*note Defining Symbols::). An additional constraint is
that the first argument of `AC_DEFINE' must be a literal. Note that
all symbols defined by Autoconf's builtin tests are already documented
properly; you only need to document 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 `#define''d (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: `autoheader''s invocation...
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:
Print a summary of the command line options and exit.
Print the version number of Autoconf and exit.
Report processing steps.
Don't remove the temporary files.
Remake the template file even if newer than its input files.
Append DIR to include path. Multiple invocations accumulate.
Prepend DIR to include path. Multiple invocations accumulate.
Report the warnings related to CATEGORY (which can actually be a
comma separated list). Current categories include:
report the uses of obsolete constructs
report all the warnings
treats warnings as errors
disable warnings falling into CATEGORY
Created Mon Nov 8 17:41:56 2004 on tillpc with info_to_html version 0.9.6.