ccache/NEWS.txt

ccache news
===========


ccache 3.0pre1 (unreleased)
---------------------------

Changes since version 2.4.


General
~~~~~~~

    - ccache is now licensed under the GNU Public License (GPL) version 3 or
      later.


Upgrade notes
~~~~~~~~~~~~~

    - The way the hashes are calculated has changed, so you won't get cache
      hits for compilation results stored by older ccache versions.

    - The statistics counters ``files in cache'' and ``cache size'' now only
      count object files. (Previously, files containing cached standard error
      output were counted as well.) The existing values of the two counters
      will be erroneous at first after the upgrade, but will correct themselves
      eventually when enough cleanups have been made, or when you run +ccache
      --cleanup+.

    - The ``max file'' and ``max cache size'' settings now specify thresholds
      for object files count and size.

    - Because of the changes mentioned above, you might as well clear the old
      cache directory with `ccache --cleanup` if you want, unless you plan to
      keep using an older ccache version.


New features and improvements
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

    - ccache now has a ``direct mode'' where it computes a hash of the source
      code (including all included files) and compiler arguments without
      running the preprocessor. By not running the preprocessor, CPU usage is
      reduced; the speed is somewhere between 1 and 5 times that of ccache
      running in traditional mode, depending on the circumstances. The speedup
      will be higher when I/O is fast (e.g., when files are in the disk cache).
      The direct mode can be disabled by setting +CCACHE_NODIRECT+.

    - Support has been added for rewriting absolute paths to relative paths
      when hashing, in order to increase cache hit rate when building the same
      source code in different directories even when compiling with `-g` and
      when using absolute include directory paths. This is done by setting the
      `CCACHE_BASEDIR` environment variable to an absolute path that specifies
      which paths to rewrite.

    - Object files are now optionally stored compressed in the cache. The
      runtime cost is negligible, and more files will fit in the ccache
      directory and in the disk cache. Set `CCACHE_COMPRESS` to enable object
      file compression. Note that you can't use compression in combination with
      the hard link feature.

    - A `CCACHE_COMPILERCHECK` option has been added. This option tells ccache
      what compiler-identifying information to hash to ensure that results
      retrieved from the cache are accurate. Possible values are: none (don't
      hash anything), mtime (hash the compiler's mtime and size) and content
      (hash the content of the compiler binary). The default is mtime.

    - It is now possible to specify extra files whose contents should be
      included in the hash sum by setting the `CCACHE_EXTRAFILES` option.

    - Temporary files are now created in the directory they will end up in.
      This makes ccache more friendly to Linux's directory layout.

    - Added support for long command-line options.

    - A `CACHEDIR.TAG` file is now created in the cache directory. See
      <http://www.brynosaurus.com/cachedir/>.

    - Messages printed to the debug log (specified by `CCACHE_LOGFILE`) have
      been improved.

    - By default, ccache now puts temporary files in `$CCACHE_DIR/tmp` to avoid
      cluttering the top directory.

    - Improved the test suite and added tests for most of the new
      functionality. It's now also possible to specify a subset of tests to
      run.

    - Standard error output from the compiler is now only stored in the cache
      if it's non-empty.

    - If the compiler produces no object file or an empty object file, but
      gives a zero exit status (could be due to a file system problem, a buggy
      program specified by `CCACHE_PREFIX`, etc.), ccache copes with it
      properly.

    - Added installcheck and distcheck make targets.

    - Clarified cache size limit options' semantics.

    - Improved display of cache max size values.

    - For debugging purposes, the variable `CCACHE_VERBOSE` may now be set to
      make ccache print executed commands to standard output.

    - The following options are no longer hashed in the preprocessor mode:
      `-imacros`, `-iprefix`, `-iwithprefix`, `-iwithprefixbefore`,
      `-nostdinc`, `-nostdinc++` and `-U`.


Bug fixes
~~~~~~~~~

    - Fixed build on FreeBSD.

    - Improved detection of home directory.

    - User-defined `CPPFLAGS` and `LDFLAGS` are now respected in the Makefile.

    - Fixed NFS issues.

    - Computation of the hash sum has been improved to decrease the risk of
      hash collisions. For instance, the compiler arguments `-X -Y` and `-X-Y`
      previously contributed equally to the hash sum.

    - Bail out on too hard compiler options `--coverage`, `-fprofile-arcs`,
      `-fprofile-generate`, `-fprofile-use`, `-ftest-coverage` and
      `-save-temps`. Also bail out on `@file` style options.

    - `-MD`/`-MMD` options without `-MT`/`-MF` are now handled correctly.

    - The `-finput-charset` option is now handled correctly.

    - Added support for `-Wp,-MD` and `-Wp,-MMD` options.

    - Debug information containing line numbers of predefined and command-line
      macros (enabled with the compiler option `-g3`) will now be correct.

    - Corrected LRU cleanup handling of object files.

    - `utimes()` is now used instead of `utime()` when available.

    - Non-writable cache directories are now handled gracefully.

    - Corrected documentation about sharing the cache directory.

    - Fixed compilation warnings from GCC 4.3.

    - The command specified by `CCACHE_PREFIX` is no longer part of the hash.

    - Fixed bad memory access spotted by Valgrind.

    - Fixed a bug in `x_realloc`.

    - Freed memory is no longer referenced when compiling a `.i`/`.ii` file and
      falling back to running the real compiler.

    - The test suite is now immune to external values of the `CCACHE_*`
      environment variables.