Make hashes path agnostic for GCC #208
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We now pass -P to the preprocessor, which inhibits the generation
of linemarkers. This has two positive side effects:
1. Absolute file paths and file names are excluded from the
preprocessor output, which makes the hash independent of
the location of the source and build directories.
2. The preprocessing step is slightly faster (in one case it
was 20% faster) and the preprocessor output is smaller (in
the aforementioned case the output was 23% smaller) which
should translate into faster hashing too.
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According to my testing, this PR fixes #207 for GCC (and hopefully Clang too). |
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Great find! Since we no longer compile from the preprocessor output this shouldn't harm anything and it fixes this longstanding issue in a simple way. I think there still might be some quirks about file paths in debug info, but we can sort that out later. It turns out MSVC does have an equivalent option: |
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Sweet! This makes sccache much more attractive for our slightly heterogeneous machine park. |
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We punted and just do all our CI builds in the same Docker image in the same paths. :) |
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We now pass -P to the preprocessor, which inhibits the generation
of linemarkers. This has two positive side effects:
Absolute file paths and file names are excluded from the
preprocessor output, which makes the hash independent of
the location of the source and build directories.
The preprocessing step is slightly faster (in one case it
was 20% faster) and the preprocessor output is smaller (in
the aforementioned case the output was 23% smaller) which
should translate into faster hashing too.