# ccache news

version 3.4.1

## ccache 3.4.1

Release date: 2018-02-11

### Bug fixes

- Fixed printing of version number in `ccache --version`.

## ccache 3.4

Release date: 2018-02-11

### New features and enhancements

- The compiler option form `--sysroot arg` is now handled like the documented `--sysroot=arg` form.

- Added support for caching `.su` files generated by GCC flag `-fstack-usage`.

- ccache should now work with distcc’s “pump” wrapper.

- The optional unifier is no longer disabled when the direct mode is enabled.

- Added support for nvcc compiler options `--compiler-bindir/-ccbin`, `--output-directory/-odir` and `--libdevice-directory/-ldir`.

- Boolean environment variable settings no longer accept the following (case-insensitive) values: `0`, `false`, `disable` and `no`. All other values are accepted and taken to mean “true”. This is to stop users from setting e.g. `CCACHE_DISABLE=0` and then expect the cache to be used.

- Improved support for `run_second_cpp = false`: If combined with passing `-fdirectives-only` (GCC) or `frewrite-includes` (Clang) to the compiler, diagnostics warnings and similar will be correct.

- An implicit `-MQ` is now passed to the preprocessor only if the object file extension is non-standard. This should make it easier to use EDG-based compilers (e.g. GHS) which don’t understand `-MQ`.

- ccache now treats an unreadable configuration file just like a missing configuration file.

- Documented more pitfalls with enabling `hard_links` (`CCACHE_HARDLINK`).

- Documented caveats related to colored warnings from compilers.

### Bug fixes

- File size and number counters are now updated correctly when files are overwritten in the cache, e.g. when using `CCACHE_RECACHE`.

- `run_second_cpp` is now forced for nvcc.

- Fixed how the nvcc options `-optf` and `-odir` are handled.

## ccache 3.3.6

Release date: 2018-01-28

### New features and enhancements

- Improved instructions on how to get cache hits between different working directories.

### Bug fixes

- Fixed regression in ccache 3.3.5 related to the `UNCACHED_ERR_FD` feature.

## ccache 3.3.5

Release date: 2018-01-13

### New features and enhancements

- Documented how automatic cache cleanup works.

### Bug fixes

- Fixed a regression where the original order of debug options could be lost. This reverts the “Improved parsing of `-g*` options” feature in ccache 3.3.

- Multiple `-fdebug-prefix-map` options should now be handled correctly.

- Fixed matching of directories in the `ignore_headers_in_manifest` configuration option.

- Fixed detection of missing argument to `-opt`/`--options-file`.

- ccache now bails out when building a precompiled header if any of the corresponding header files have an updated timestamp. This fixes complaints from clang.

- Fixed a bug related to erroneously storing a dependency file with absolute paths in the cache on a preprocessed hit.

- `ccache -c/--cleanup` now works like documented: it just recalculates size counters and trims the cache to not exceed the max size and file number limits. Previously, the forced cleanup took “limit_multiple” into account, so that `ccache -c/--cleanup` by default would trim the cache to 80% of the max limit.

- ccache no longer ignores linker arguments for clang since clang warns about them.

- Plugged a couple of file descriptor leaks.

- Fixed a bug where ccache would skip hashing the compiler argument following a `-fno-working-directory`, `-fworking-directory`, `-nostdinc`, `-nostdinc++`, `-remap` or `-trigraphs` option in preprocessor mode.

## ccache 3.3.4

Release date: 2017-02-17

### New features and enhancements

- Documented the different cache statistics counters.

### Bug fixes

- Fixed a regression in ccache 3.3 related to potentially bad content of dependency files when compiling identical source code but with different source paths. This was only partially fixed in 3.3.2 and reverts the new “Names of included files are no longer included in the hash of the compiler’s preprocessed output” feature in 3.3.

- Corrected statistics counter for `-optf`/`--options-file` failure.

- Fixed undefined behavior warnings in ccache found by `-fsanitize=undefined`.

## ccache 3.3.3

Release date: 2016-10-26

### Bug fixes

- ccache now detects usage of `.incbin` assembler directives in the source code and avoids caching such compilations.

## ccache 3.3.2

Release date: 2016-09-28

### Bug fixes

- Fixed a regression in ccache 3.3 related to potentially bad content of dependency files when compiling identical source code but with different source paths.

- Fixed a regression in ccache 3.3.1: ccache could get confused when using the compiler option `-Wp,` to pass multiple options to the preprocessor, resulting in missing dependency files from direct mode cache hits.

## ccache 3.3.1

Release date: 2016-09-07

### Bug fixes

- Fixed a problem in the “multiple `-arch` options” support introduced in 3.3. When using the direct mode (the default), different combinations of `-arch` options were not detected properly.

- Fixed an issue when compiler option `-Wp,-MT,path` is used instead of `-MT path` (and similar for `-MF`, `-MP` and `-MQ`) and `run_second_cpp` (`CCACHE_CPP2`) is enabled.

## ccache 3.3

Release date: 2016-08-27

### Notes

- A C99-compatible compiler is now required to build ccache.

### New features and enhancements

- The configuration option `run_second_cpp` (`CCACHE_CPP2`) now defaults to true. This improves ccache’s out-of-the-box experience for compilers that can’t compile their own preprocessed output with the same outcome as if they compiled the real source code directly, e.g. newer versions of GCC and Clang.

- The configuration option `hash_dir` (`CCACHE_HASHDIR`) now defaults to true.

- Added a new `ignore_headers_in_manifest` configuration option, which specifies headers that should be ignored in the direct mode.

- Added a new `prefix_command_cpp` (`CCACHE_PREFIX_CPP`) configuration option, which specifies one or several prefixes to add to the command line ccache uses when invoking the preprocessor.

- Added a new `limit_multiple` (`CCACHE_LIMIT_MULTIPLE`) configuration option, which specifies how much of the cache to remove when cleaning.

- Added a new `keep_comments_cpp` (`CCACHE_COMMENTS`) configuration option, which tells ccache not to discard the comments before hashing preprocessor output. This can be used to check documentation with -Wdocumentation.

- Added a new sloppiness option `no_system_headers`, which tells ccache not to include system headers in manifest files.

- Added a new statistics counter that tracks the number of performed cleanups due to the cache size being over the limit. The value is shown in the output of “ccache -s”.

- Added support for relocating debug info directory using `-fdebug-prefix-map`. This allows for cache hits even when `hash_dir` is used in combination with `base_dir`.

- Added a new “cache hit rate” field to the output of “ccache -s”.

- Added support for caching compilation of assembler code produced by e.g. “gcc -S file.c”.

- Added support for cuda including the -optf/--options-file option.

- Added support for Fortran 77.

- Added support for multiple `-arch` options to produce "fat binaries".

- Multiple identical `-arch` arguments are now handled without bailing.

- The concatenated form of some long compiler options is now recognized, for example when using `-isystemPATH` instead of `-isystem PATH`.

- If hard-linking is enabled and but fails (e.g. due to cross-device linking), ccache now falls back to copying instead of running the compiler.

- Made the `hash_dir` option only have effect when generating debug info.

- ccache now knows how to convert absolute paths to relative paths inside dependency files when using `base_dir`.

- Improved parsing of `-g*` options.

- Made ccache understand `-Wp,-D*` options.

- ccache now understands the undocumented `-coverage` (only one dash) GCC option.

- Names of included files are no longer included in the hash of the compiler’s preprocessed output. This leads to more potential cache hits when not using the direct mode.

- Increased buffer size used when reading file data. This improves performance slightly.

### Bug fixes

- Bail out on too hard compiler option `-P`.

- Fixed clang test suite when running on Linux.

- Fixed build and test for MinGW32 and Windows.

## ccache 3.2.9

Release date: 2016-09-28

### Bug fixes

- Fixed a regression in ccache 3.2.8: ccache could get confused when using the compiler option `-Wp,` to pass multiple options to the preprocessor, resulting in missing dependency files from direct mode cache hits.

## ccache 3.2.8

Release date: 2016-09-07

### Bug fixes

- Fixed an issue when compiler option `-Wp,-MT,path` is used instead of `-MT path` (and similar for `-MF`, `-MP` and `-MQ`) and `run_second_cpp` (`CCACHE_CPP2`) is enabled.

- ccache now understands the undocumented `-coverage` (only one dash) GCC option.

## ccache 3.2.7

Release date: 2016-07-20

### Bug fixes

- Fixed a bug which could lead to false cache hits for compiler command lines with a missing argument to an option that takes an argument.

- ccache now knows how to work around a glitch in the output of GCC 6’s preprocessor.

## ccache 3.2.6

Release date: 2016-07-12

### Bug fixes

- Fixed build problem on QNX, which lacks “SA_RESTART”.

- Bail out on compiler option `-fstack-usage` since it creates a `.su` file which ccache currently doesn’t handle.

- Fixed a bug where (due to ccache rewriting paths) the compiler could choose incorrect include files if `CCACHE_BASEDIR` is used and the source file path is absolute and is a symlink.

## ccache 3.2.5

Release date: 2016-04-17

### New features and enhancements

- Only pass clang-specific `-stdlib=` to the preprocessor.

- Improved handling of stale NFS handles.

- Made it harder to misinterpret documentation of boolean environment settings' semantics.

### Bug fixes

- Include m4 files used by configure.ac in the source dist archives.

- Corrected "Performance" section in the manual regarding `__DATE_`, `__TIME__` and `__FILE__` macros.

- Fixed build on Solaris 10+ and AIX 7.

- Fixed failure to create directories on QNX.

- Don’t (try to) update manifest file in “read-only” and “read-only direct” modes.

- Fixed a bug in caching of `stat` system calls in “file_stat_matches sloppiness mode”.

- Fixed bug in hashing of clang plugins, leading to unnecessary cache misses.

- Fixed --print-config to show “pch_defines sloppiness”.

- The man page is now built when running “make install” from Git repository sources.

## ccache 3.2.4

Release date: 2015-10-08

### Bug fixes

- Fixed build error related to zlib on systems with older make versions (regression in ccache 3.2.3).

- Made conversion-to-bool explicit to avoid build warnings (and potential runtime errors) on legacy systems.

- Improved signal handling: Kill compiler on SIGTERM; wait for compiler to exit before exiting; die appropriately.

- Minor fixes related to Windows support.

- The correct compression level is now used if compression is requested.

- Fixed a bug where cache cleanup could be run too early for caches larger than 64 GiB on 32-bit systems.

## ccache 3.2.3

Release date: 2015-08-16

### New features and enhancements

- Added support for compiler option `-gsplit-dwarf`.

### Bug fixes

- Support external zlib in nonstandard directory.

- Avoid calling `exit()` inside an exit handler.

- Let exit handler terminate properly.

- Bail out on compiler option `--save-temps` in addition to `-save-temps`.

- Only log "Disabling direct mode" once when failing to read potential include files.

## ccache 3.2.2

Release date: 2015-05-10

### New features and enhancements

- Added support for `CCACHE_COMPILERCHECK=string:<value>`. This is a faster alternative to `CCACHE_COMPILERCHECK=<command>` if the command’s output can be precalculated by the build system.

- Add support for caching code coverage results (compiling for gcov).

### Bug fixes

- Made hash of cached result created with and without `CCACHE_CPP2` different. This makes it possible to rebuild with `CCACHE_CPP2` set without having to clear the cache to get new results.

- Don’t try to reset a non-existing stats file. This avoids “No such file or directory” messages in the ccache log when the cache directory doesn’t exist.

- Fixed a bug where ccache deleted clang diagnostics after compiler failures.

- Avoid performing an unnecessary copy of the object file on a cache miss.

- Bail out on too hard compiler option `-fmodules`.

- Bail out on too hard compiler option `-fplugin=libcc1plugin` (interaction with GDB).

- Fixed build error when compiling ccache with recent clang versions.

- Removed signal-unsafe code from signal handler.

- Corrected logic for when to output cached stderr.

- Wipe the whole cached result on failure retrieving a cached file.

- Fixed build error when compiling ccache with recent clang versions.

## ccache 3.2.1

Release date: 2014-12-10

### Bug fixes

- Fixed regression in temporary file handling, which lead to incorrect permissions for stats, manifest and ccache.conf files in the cache.

- `CACHEDIR.TAG` files are now created in the [0-9a-f] subdirectories so that ccache.conf is not lost in backups.

- Made the default cache size suffix `G`, as previously documented.

- `-fdiagnostics-color=auto` is now passed to the compiler even if stderr is redirected. This fixes a problem when, for instance, a configure test probes if the compiler (wrapped via ccache) supports `-fdiagnostics-color=auto`.

- Added missing documentation for `max_files` and `max_size` configuration options.

## ccache 3.2

Release date: 2014-11-17

### New features and enhancements

- Added support for configuring ccache via one or several configuration files instead of via environment variables. Environment variables still have priority but are no longer the recommended way of customizing ccache behavior. See the manual for more information.

- Added support for compiler error/warning messages with color.

- Made creation of temporary directories and cache directories smarter to avoid unnecessary `stat` calls.

- Improved efficiency of the algorithm that scans for `__DATE_` and `__TIME__` tokens in the hashed source code.

- Added support for several binaries (separated by space) in `CCACHE_PREFIX`.

- The `-c` option is no longer passed to the preprocessor. This fixes problems with clang and Solaris’s C++ compiler.

- ccache no longer passes preprocessor options like `-D` and `-I` to the compiler when compiling preprocessed output. This fixes warnings emitted by clang.

- Compiler options `-fprofile-generate`, `-fprofile-arcs`, `-fprofile-use` and `-fbranch-probabilities` are now handled without bailing.

- Added support for clang’s `--serialize-diagnostic` option, storing the diagnostic file (`.dia`) in the cache.

- Added support for precompiled headers when using clang.

- Added support for clang `.pth` (pretokenized header) files.

- Changed the `-x` language option to use the new objective C standard for GCC and clang.

- On a cache miss, ccache now instructs the compiler to create the object file at the real destination and then copies the file into the cache instead of the other way around. This is needed to support compiler options like `-fprofile-arcs` and `--serialize-diagnostics`.

- ccache now checks that included files' ctimes aren’t too new. This check can be turned off by adding `include_file_ctime` to the “ccache sloppiness” setting.

- Added possibility to get cache hits based on filename, size, mtime and ctime only. On other words, source code files are not even read, only stat-ed. This operation mode is opt-in by adding `file_stat_matches` to the “ccache sloppiness” setting.

- The filename part of options like `-Wp,-MDfilename` is no longer included in the hash since the filename doesn’t have any bearing on the result.

- Added a “read-only direct” configuration setting, which is like the ordinary read-only setting except that ccache will only try to retrieve results from the cache using the direct mode, not the preprocessor mode.

- The display and interpretation of cache size has been changed to use SI units.

- Default cache size is now 5 GB (was previously 1 GiB).

- Added configuration option to set the compression level of compressed object files in the cache.

- Added support for `@file` and `-@file` arguments (reading options from a file).

- `-Wl,` options are no longer included in the hash since they don’t affect compilation.

- Bail out on too hard compiler option `-Wp,-P`.

- Optimized MD4 calculation code on little-endian systems.

- Various improvements and fixes on win32.

- Improved logging to the ccache log file.

- Added `--dump-manifest` command-line option for debugging purposes.

- Added `--with-bundled-zlib` configure option.

- Upgraded bundled zlib to version 1.2.8.

- Improved `dev.mk` to be more platform independent.

- Made the test suite work with clang and gcc-llvm on OS X.

- Various other improvements of the test suite.

### Bug fixes

- Any previous `.stderr` is now removed from the cache when recaching.

- Fixed an issue when handling the `-arch` compiler option with an argument.

- Fixed race condition when creating the initial cache directory.

- Fixed test suite failures when `CC` is a ccache-wrapped compiler.

## ccache 3.1.12

Release date: 2016-07-12

### Bug fixes

- Fixed a bug where (due to ccache rewriting paths) the compiler could choose incorrect include files if `CCACHE_BASEDIR` is used and the source file path is absolute and is a symlink.

## ccache 3.1.11

Release date: 2015-03-07

### Bug fixes

- Fixed bug which could result in false cache hits when source code contains `'"'` followed by `" /*"` or `" //"` (with variations).

- Made hash of cached result created with and without `CCACHE_CPP2` different. This makes it possible to rebuild with `CCACHE_CPP2` set without having to clear the cache to get new results.

- Don’t try to reset a non-existing stats file. This avoids “No such file or directory” messages in the ccache log when the cache directory doesn’t exist.

## ccache 3.1.10

Release date: 2014-10-19

### New features and enhancements

- Added support for the `-Xclang` compiler option.

- Improved handling of exit code of internally executed processes.

- Zero length object files in the cache are now rejected as invalid.

- Bail out on option `-gsplit-dwarf` (since it produces multiple output files).

- Compiler option `-fdebug-prefix-map` is now ignored (not part of the hash). (The `-fdebug-prefix-map` option may be used in combination with `CCACHE_BASEDIR` to reuse results across different directories.)

- Added note in documentation that `--ccache-skip` currently does not mean “don’t hash the following option”.

- To enable support for precompiled headers (PCH), `CCACHE_SLOPPINESS` now also needs to include the new `pch_defines` sloppiness. This is because ccache can’t detect changes in the source code when only defined macros have been changed.

- Stale files in the internal temporary directory (`<ccache_dir>/tmp`) are now cleaned up if they are older than one hour.

### Bug fixes

- Fixed path canonicalization in `make_relative_path()` when path doesn’t exist.

- Fixed bug in `common_dir_prefix_length()`. This corrects the `CCACHE_BASEDIR` behavior.

- ccache no longer tries to create the cache directory when `CCACHE_DISABLE` is set.

- Fixed bug when reading manifests with a very large number of file info entries.

- Fixed problem with logging of current working directory.

## ccache 3.1.9

Release date: 2013-01-06

### Bug fixes

- The EAGAIN signal is now handled correctly when emitting cached stderr output. This fixes a problem triggered by large error outputs from the compiler.

- Subdirectories in the cache are no longer created in read-only mode.

- Fixed so that ccache’s log file descriptor is not made available to the compiler.

- Improved error reporting when failing to create temporary stdout/stderr files when executing the compiler.

- Disappearing temporary stdout/stderr files are now handled gracefully.

### Other

- Fixed test suite to work on ecryptfs.

## ccache 3.1.8

Release date: 2012-08-11

### New features and enhancements

- Made paths to dependency files relative in order to increase cache hits.

- Added work-around to make ccache work with buggy GCC 4.1 when creating a pre-compiled header.

- Clang plugins are now hashed to catch plugin upgrades.

### Bug fixes

- Fixed crash when the current working directory has been removed.

- Fixed crash when stderr is closed.

- Corrected a corner case when parsing backslash escapes in string literals.

- Paths are now correctly canonicalized when computing paths relative to the base directory.

### Other

- Made git version macro work when compiling outside of the source directory.

- Fixed `static_assert` macro definition clash with GCC 4.7.

## ccache 3.1.7

Release date: 2012-01-08

### Bug fixes

- Non-writable `CCACHE_DIR` is now handled gracefully when `CCACHE_READONLY` is set.

- Made failure to create files (typically due to bad directory permissions) in the cache directory fatal. Previously, such failures were silently and erroneously flagged as "compiler produced stdout".

- Both the `-specs=file` and `--specs=file` forms are now recognized.

- Added recognition and hashing of GCC plugins specified with `-fplugin=file`.

- `CCACHE_COMPILERCHECK` now also determines how to hash explicit specs files (`-specs=file`).

- Added `CPATH`, `C_INCLUDE_PATH` and similar environment variables to the hash to avoid false cache hits when such variables have changed.

- Corrected log message when unify mode is enabled.

- Reverted the GCC bug compatibility introduced in ccache 3.1.5 for `-MT`/`-MQ` options with concatenated arguments. (The bug is fixed in recent GCC versions.)

### Other

- Corrected license header for `mdfour.c`.

- Improved documentation on how to fix bad object files in the cache.

## ccache 3.1.6

Release date: 2011-08-21

### New features and enhancements

- Rewrite argument to `--sysroot` if `CCACHE_BASEDIR` is used.

### Bug fixes

- Don’t crash if `getcwd()` fails.

- Fixed alignment of “called for preprocessing” counter.

## ccache 3.1.5

Release date: 2011-05-29

### New features and enhancements

- Added a new statistics counter named “called for preprocessing”.

- The original command line is now logged to the file specified with `CCACHE_LOGFILE`.

- Improved error logging when system calls fail.

- Added support for rewriting absolute paths in `-F`/`-iframework` GCC options.

- Improved order of statistics counters in `ccache -s` output.

### Bug fixes

- The `-MF`/`-MT`/`-MQ` options with concatenated argument are now handled correctly when they are last on the command line.

- ccache is now bug compatible with GCC for the `-MT`/`-MQ` options with concatenated arguments.

- Fixed a minor memory leak.

- Systems that lack (and don’t need to be linked with) libm are now supported.

## ccache 3.1.4

Release date: 2011-01-09

### Bug fixes

- Made a work-around for a bug in `gzputc()` in zlib 1.2.5.

- Corrupt manifest files are now removed so that they won’t block direct mode hits.

- ccache now copes with file systems that don’t know about symbolic links.

- The file handle in now correctly closed on write error when trying to create a cache dir tag.

## ccache 3.1.3

Release date: 2010-11-28

### Bug fixes

- The -MFarg, -MTarg and -MQarg compiler options (i.e, without space between option and argument) are now handled correctly.

### Other

- Portability fixes for HP-UX 11.00 and other esoteric systems.

## ccache 3.1.2

Release date: 2010-11-21

### Bug fixes

- Bail out on too hard compiler options `-fdump-*`.

- NULL return values from malloc/calloc of zero bytes are now handled correctly.

- Fixed issue when parsing precompiler output on AIX.

### Other

- Improved documentation on which information is included in the hash sum.

- Made the “too new header file” test case work on file systems with unsynchronized clocks.

- The test suite now also works on systems that lack a /dev/zero.

## ccache 3.1.1

Release date: 2010-11-07

### Bug fixes

- ccache now falls back to preprocessor mode when a non-regular include file (device, socket, etc) has been detected so that potential hanging due to blocking reads is avoided.

- CRC errors are now detected when decompressing compressed files in the cache.

- Fixed potential object file corruption race on NFS.

- Minor documentation corrections.

- Fixed configure detection of ar.

- ccache development version (set by dev.mk) now works with gits whose `describe` command doesn’t understand `--dirty`.

### Other

- Minor debug log message improvements.

## ccache 3.1

Release date: 2010-09-16

### New features and enhancements

- Added support for hashing the output of a custom command (e.g. `%compiler% --version`) to identify the compiler instead of stat-ing or hashing the compiler binary. This can improve robustness when the compiler (as seen by ccache) actually isn’t the real compiler but another compiler wrapper.

- Added support for caching compilations that use precompiled headers. (See the manual for important instructions regarding this.)

- Locking of the files containing statistics counters is now done using symlinks instead of POSIX locks. This should make ccache behave a lot better on file systems where POSIX locks are slow or broken (e.g. NFS on some systems).

- Manifest files are now updated without the need of taking locks.

- Updates of statistics counters are now always done in one of the sub-level statistics files. This reduces lock contention, which especially improves performance on slow NFS mounts.

- Reading and writing of statistics counters has been made forward-compatible (unknown counters are retained).

- Files are now read without using `mmap()`. This has two benefits: it’s more robust against file changes during reading and it improves performance on poor systems where `mmap()` doesn’t use the disk cache.

- Added `.cp` and `.CP` as known C++ suffixes.

- Improved logging.

- Added `-install_name` as an option known to take an argument. (This improves statistics when using the Darwin linker.)

### Bug fixes

- Non-fatal error messages are now never printed to stderr but logged instead.

- Fixed a bug affecting failing commands when `--ccache-skip` is used.

- Made `--ccache-skip` work for all options.

- EINTR is now handled correctly.

### Other

- Work on porting ccache to win32 (native), mostly done by Ramiro Polla. The port is not yet finished, but will hopefully be complete in some subsequent release.

- Added a `--nostats` flag to the performance benchmark program.

- Made the performance benchmark program more accurate when measuring cache hits.

- Added a new test framework for unit tests written in C.

- Got rid of `configure-dev`; dev mode is now given by `dev.mk.in` presence.

- Improved documentation on how to combine ccache with other compiler wrappers (like `distcc`).

- New `LICENSE.txt` file with licensing and copyright details about bundled source code.

- New `AUTHORS.txt` file with a list of ccache contributors.

- New `HACKING.txt` file with some notes about ccache code conventions.

## ccache 3.0.1

Release date: 2010-07-15

### Bug fixes

- The statistics counter “called for link” is now correctly updated when linking with a single object file.

- Fixed a problem with out-of-source builds.

## ccache 3.0

Release date: 2010-06-20

### General

- ccache is now licensed under the GNU General 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. Because of this, you might as well clear the old cache directory with `ccache --clear` if you want, unless you plan to keep using an older ccache version.

### New features and enhancements

- ccache now has a “direct mode” where it computes a hash of the source code (including all included files) and compiler options 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.

- Added support for Objective-C and Objective-C++. The statistics counter “not a C/C++ file” has been renamed to “unsupported source language”.

- Added support for the `-x` compiler option.

- 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.

- You can relax some checks that ccache does in direct mode by setting `CCACHE_SLOPPINESS`. See the manual for more information.

- `CCACHE_TEMPDIR` no longer needs to be on the same filesystem as `CCACHE_DIR`.

- The default value of `CCACHE_TEMPDIR` has been changed to `$CCACHE_DIR/tmp` to avoid cluttering the top directory.

- Temporary files that later will be moved into the cache are now created in the cache directory they will end up in. This makes ccache more friendly to Linux’s directory layout.

- 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' and cleanup semantics.

- Improved display of cache max size values.

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

### Bug fixes

- Various portability improvements.

- 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 options `-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`, `-frepo`, `-ftest-coverage` and `-save-temps`. Also bail out on `@file` style options.

- Errors when using multiple `-arch` compiler options are now noted as “unsupported compiler option”.

- `-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.

- The compiler options `-Xassembler`, `-b`, `-G` and `-V` are now correctly recognized as taking an argument.

- 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.

- Improved detection of recursive invocation.

- The ccache binary is now not unconditionally stripped when installing.

- Statistics counters are now correctly updated for -E option failures and internal errors.