ccache only caches the individual object files produced by compiling a .cpp file. C++ build times are actually dominated by redundant parsing of headers includ

ccache only caches the individual object files produced by compiling a .cpp file. C++ build times are actually dominated by redundant parsing of headers included in multiple .cpp files. And also redundant template instantiations in different files. This redundancy still exists when using ccache. By caching the individual language constructs, you eliminate the redundancy entirely.