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22 lines
1.1 KiB
Markdown
22 lines
1.1 KiB
Markdown
# Compilation caching (CompilationCaching)
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Errors and warnings related to the compiler's CAS compilation caching.
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## Overview
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Compilation caching allows Swift compiler to reuse previously compiled outputs if the identical
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compilation has been done before.
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When compilation caching is enabled (via `-cache-compile-job` flag), the build commands are
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expected to be generated by Swift driver, and the command-line of compilation tasks contains
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CASIDs that are objects constructed during planning phase. These CAS objects need to be backed
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by CAS storage and in a specific scheme accepted by the compiler. Any malformed command-line
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will cause error in this category. If the inputs changed, always fallback to re-run `swiftc`
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command to plan the new build commands.
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The other category of error is unexpected failures when performing reads/writes to Content
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Addressable Storage. Please refer to the error message (contains errors provided by CAS storage) for clues.
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If the error persists, consider clearing the cache. To clear the cache, delete the directory
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pointed to by the `-cas-path` option. Note that the CAS directory should only be deleted as a whole when not used.
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