ccache

Ccache is a solution to try and speed up incremental builds of C/C++ code by figuring a smart way to “cache” on disc object files generated by a C/C++ compiler.

ccache simulates the C preprocessor, calculates an MD5 hash and if the hash has not changed then we can just copy the object file from the cache rather than re-invoking the compiler.

ccache usually consumes a fair bit of disc space. I wouldn’t take it for granted that ccache always works - your mileage may vary depending on what version someone is running.

For more information:

Ccache — Compiler cache

You can see the state of ccache with the -s flag which gives much more clarity as to what it is doing:

Eliots-MacBook-Pro-2:COL eliotmuir$ ccache -s
cache directory                     /Users/eliotmuir/.ccache
primary config                      /Users/eliotmuir/.ccache/ccache.conf
secondary config      (readonly)    /usr/local/Cellar/ccache/3.7.4/etc/ccache.conf
stats updated                       Wed Sep  1 11:35:53 2021
stats zeroed                        Sat Apr  3 17:41:13 2021
cache hit (direct)                110141
cache hit (preprocessed)            4424
cache miss                         22688
cache hit rate                     83.47 %
called for link                     5700
called for preprocessing              13
multiple source files                  3
compiler produced empty output         2
compile failed                       996
preprocessor error                   985
bad compiler arguments                 1
autoconf compile/link                 42
no input file                          5
cleanups performed                     0
files in cache                     55462
cache size                           2.5 GB
max cache size                       5.0 GB

Concepts

ccache

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