(autocf21.info.gz) Caching Results
Info Catalog
(autocf21.info.gz) Setting Output Variables
(autocf21.info.gz) Results
(autocf21.info.gz) Printing Messages
6.3 Caching Results
===================
To avoid checking for the same features repeatedly in various
`configure' scripts (or repeated runs of one script), `configure' saves
the results of many of its checks in a "cache file". If, when a
`configure' script runs, it finds a cache file, it reads from it the
results from previous runs and avoids rerunning those checks. As a
result, `configure' can run much faster than if it had to perform all
of the checks every time.
-- Macro: AC_CACHE_VAL (CACHE-ID, COMMANDS-TO-SET-IT)
Ensure that the results of the check identified by CACHE-ID are
available. If the results of the check were in the cache file
that was read, and `configure' was not given the `--quiet' or
`--silent' option, print a message saying that the result was
cached; otherwise, run the shell commands COMMANDS-TO-SET-IT.
Those commands should have no side effects except for setting the
variable CACHE-ID. In particular, they should not call
`AC_DEFINE'; the code that follows the call to `AC_CACHE_VAL'
should do that, based on the cached value. Also, they should not
print any messages, for example with `AC_MSG_CHECKING'; do that
before calling `AC_CACHE_VAL', so the messages are printed
regardless of whether the results of the check are retrieved from
the cache or determined by running the shell commands. If the
shell commands are run to determine the value, the value will be
saved in the cache file just before `configure' creates its output
files. Cache Variable Names, for how to choose the name
of the CACHE-ID variable.
-- Macro: AC_CACHE_CHECK (MESSAGE, CACHE-ID, COMMANDS)
A wrapper for `AC_CACHE_VAL' that takes care of printing the
messages. This macro provides a convenient shorthand for the most
common way to use these macros. It calls `AC_MSG_CHECKING' for
MESSAGE, then `AC_CACHE_VAL' with the CACHE-ID and COMMANDS
arguments, and `AC_MSG_RESULT' with CACHE-ID.
-- Macro: AC_CACHE_LOAD
Loads values from existing cache file, or creates a new cache file
if a cache file is not found. Called automatically from `AC_INIT'.
-- Macro: AC_CACHE_SAVE
Flushes all cached values to the cache file. Called automatically
from `AC_OUTPUT', but it can be quite useful to call
`AC_CACHE_SAVE' at key points in configure.in. Doing so
checkpoints the cache in case of an early configure script abort.
Menu
* Cache Variable Names Shell variables used in caches.
* Cache Files Files `configure' uses for caching.
Info Catalog
(autocf21.info.gz) Setting Output Variables
(autocf21.info.gz) Results
(autocf21.info.gz) Printing Messages
automatically generated byinfo2html