54 lines
2.5 KiB
Markdown
54 lines
2.5 KiB
Markdown
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This is a system of building and caching dependencies necessary for building Bitcoin.
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There are several features that make it different from most similar systems:
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### It is designed to be builder and host agnostic
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In theory, binaries for any target OS/architecture can be created, from a
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builder running any OS/architecture. In practice, build-side tools must be
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specified when the defaults don't fit, and packages must be amended to work
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on new hosts. For now, a build architecture of x86_64 is assumed, either on
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Linux or OSX.
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### No reliance on timestamps
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File presence is used to determine what needs to be built. This makes the
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results distributable and easily digestable by automated builders.
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### Each build only has its specified dependencies available at build-time.
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For each build, the sysroot is wiped and the (recursive) dependencies are
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installed. This makes each build deterministic, since there will never be any
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unknown files available to cause side-effects.
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### Each package is cached and only rebuilt as needed.
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Before building, a unique build-id is generated for each package. This id
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consists of a hash of all files used to build the package (Makefiles, packages,
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etc), and as well as a hash of the same data for each recursive dependency. If
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any portion of a package's build recipe changes, it will be rebuilt as well as
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any other package that depends on it. If any of the main makefiles (Makefile,
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funcs.mk, etc) are changed, all packages will be rebuilt. After building, the
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results are cached into a tarball that can be re-used and distributed.
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### Package build results are (relatively) deterministic.
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Each package is configured and patched so that it will yield the same
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build-results with each consequent build, within a reasonable set of
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constraints. Some things like timestamp insertion are unavoidable, and are
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beyond the scope of this system. Additionally, the toolchain itself must be
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capable of deterministic results. When revisions are properly bumped, a cached
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build should represent an exact single payload.
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### Sources are fetched and verified automatically
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Each package must define its source location and checksum. The build will fail
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if the fetched source does not match. Sources may be pre-seeded and/or cached
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as desired.
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### Self-cleaning
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Build and staging dirs are wiped after use, and any previous version of a
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cached result is removed following a successful build. Automated builders
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should be able to build each revision and store the results with no further
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intervention.
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