FWIW, it sounds pretty sexy to me! :-)
Question: for an NFS-mounted cache, wouldn't different users' CCACHE_MAX
values conflict? It seems to me it's better as a one-time or per-cache setting.
I can definitely see how it would have value in a single-user setup, though.
Original message
Date: Wed, 06 Apr 2011 22:12:55 +0200
From: ccache-boun...@lists.samba.org (on behalf of Joel Rosdahl
j...@rosdahl.net)
Subject: [ccache] Configuration file plan
To: ccache list ccache@lists.samba.org
Hi,
I would like to improve ccache's configurability. As you know, configuration of
ccache is today done by setting a bunch of environment variables, but that's
becoming increasingly messy; there are currently 24 CCACHE_* variables in the
development version of ccache. I think it's time to move settings to a
configuration file while keeping the ability to override configuration by
setting environment variables.
I actually envision two configuration files:
- sysconfdir/ccache.conf (typically /etc/ccache.conf)
- ccachedir/ccache.conf (typically $HOME/.ccache/ccache.conf)
ccache reads both (if they exist) each time it's run. Settings then have the
following priority:
1. Environment variables.
2. ccachedir/ccache.conf
3. sysconfdir/ccache.conf
4. Compile-time defaults.
This means that:
- The administrator can choose default settings for the system by editing
sysconfdir/ccache.conf.
- The user can override the system settings with his/her own default settings
by editing ccachedir/ccache.conf. (If ccachedir is shared by several
users, the settings are of course also shared.)
- The user can override the default settings temporarily by setting environment
variables.
- It's backwards compatible with the existing environment variables.
I expect that the overhead of reading the configuration file(s) will be
negligible.
The max files and max size settings (set by command-line options
-F/--max-files and -M/--max-size) are today stored in the stats files in the
cache, but these will find a much better place in ccachedir/ccache.conf.
I think the configuration file syntax should be a simple text format like this:
# A comment.
key = value
No quotes around strings (at least not mandatory). Whitespace is trimmed at the
beginning and end of values.
Mapping between environment variables and keys in the configuration files:
Environment variable Config key Type Default Note
---
CCACHE_BASEDIR base_dir string [1]
CCACHE_CC compiler string [2]
CCACHE_COMPILERCHECK compiler_check string mtime
CCACHE_COMPRESScompression boolean false
CCACHE_CPP2run_second_cpp boolean false
CCACHE_DETECT_SHEBANG detect_shebang boolean false
CCACHE_DIR cache_dirstring $HOME/.ccache
CCACHE_DIRECT direct_mode boolean true
CCACHE_DISABLE disable boolean false
CCACHE_EXTENSION cpp_extensionstring [3]
CCACHE_EXTRAFILES extra_files_to_hash string
CCACHE_HARDLINKhard_linkboolean false
CCACHE_HASHDIR hash_dir boolean false
CCACHE_LOGFILE log_file string [4]
NEW CCACHE_MAXFILESmax_filesinteger 0 [5]
NEW CCACHE_MAXSIZE max_size integer 1G[6]
CCACHE_NLEVELS cache_dir_levels integer 2
CCACHE_PATHpath string [7]
CCACHE_PREFIX prefix_command string [8]
CCACHE_READONLYread_onlyboolean false
CCACHE_RECACHE recache boolean false
CCACHE_SLOPPINESS sloppiness string
CCACHE_STATS statsboolean true
CCACHE_TEMPDIR temporary_dirstring [9]
CCACHE_UMASK umaskinteger - [10]
CCACHE_UNIFY unifyboolean false
String and integer settings are handled in a straight-forward manner, but
boolean settings are a bit special for backward-compatibility reasons:
- A boolean CCACHE_FOO set to any value (even the empty string) means true;
unset means false.
- For each boolean CCACHE_FOO, there is also a CCACHE_NOFOO with the inverse
logic. CCACHE_FOO (if set) has higher priority than CCACHE_NOFOO. (Some
settings are quite silly in their NO variant, but I think it's worth it for
consistency.)
- The possible values of a boolean setting in the configuration file are
spelled true and false.
$VARIABLE and ${VARIABLE} references will be expanded as expected in variables
that specify paths.
Notes:
[1] The empty string
