Fix Bazel build instructions and elaborated them #2
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The `bazel` call that utilized a local LLVM installation failed with linker errors because the link order of LLVM libraries wasn't in dependency order. The fix is to utilize LLD via the `-fuse-ld` flag. LLD, unlike traditional Unix-like linkers, allows for reverse dependencies (aka backrefs. See the --warn-backrefs option). Note that the `-fuse-id` flag was being used for the Bazel-provided LLVM installation configuration. Several other changes were made: * The build system was broken into two sections: install dependencies and build crubit. This was done since the former usually need be done only once. * Modified the installation instructions to install bazelisk as the system installation of bazel was incorrect (the package name is actually bazel-bootstrap) and, even if it were correct, would install a version that is too old. * Clarified the two build options and the reasons why one would prefer one to the other. * Modified the local LLVM option to build and use `lld`. This reduces variance of tooling used to build this project. * Added `$LLVM_INSTALL_PATH/bin` to the `PATH` so this compiler is selected instead of any system installations.
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Well, there's only one right now, but it's structured so that we can do more later. This is the second time I'm implementing this, and the second implementation is much cleaner: to track the error messages, etc., I just use a fine grained enum. That's it! Doing something with string values is a bad idea. :( Deployment plan for this CL (and any other CLs that gate to experimental): - [x] wait until a version of crubit that accepts feature flags is released to the stable toolchain. - [x] change the bzl to implicitly pass in `:experimental` to all targets -- done in 1fd4aec - [ ] it's now safe to submit gating CLs, including this one. - [ ] once we're done gating features, apply `:experimental` _manually_ to all targets that need it, and submit a bzl change that reverts #2. (Which targets to apply `:experimental` to, can be determined by the breakage list from the CL reverting #2.) PiperOrigin-RevId: 676632613 Change-Id: I693be7e380bfefef3db898a9f02512c678148fd9
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The
bazelcall that utilized a local LLVM installation failed withlinker errors because the link order of LLVM libraries wasn't in
dependency order. The fix is to utilize LLD via the
-fuse-ldflag. LLD,unlike traditional Unix-like linkers, allows for reverse dependencies
(aka backrefs. See the --warn-backrefs option). Note that the
-fuse-idflag was being used for the Bazel-provided LLVM installation configuration.
Several other changes were made:
build crubit. This was done since the former usually need be done only
once.
system installation of bazel was incorrect (the package name is actually
bazel-bootstrap) and, even if it were correct, would install a version
that is too old.
one to the other.
lld. This reducesvariance of tooling used to build this project.
$LLVM_INSTALL_PATH/binto thePATHso this compiler is selectedinstead of any system installations.