Hello,
git bisect helped me today in tracking down a regression in LLVM/Clang. Because LLVM/Clang code is split across multiple git repositories, there were a few obstacles to overcome prior to using git bisect. I thought I would share them here, in the hope that they’re useful for others.
The main difficulty was to check out the version of clang and compiler-rt that would compile with a given LLVM revision. I used the following code in the bisect script:
checkout() {
cd $LLVM_SRC
local committer_date=“$(git log --pretty=format:%cd -n1 ‘HEAD’)”
cd $LLVM_SRC/tools/clang
git checkout “$(git rev-list -n 1 --before=”$committer_date" origin/google/testing)"
cd $LLVM_SRC/projects/compiler-rt
git checkout “$(git rev-list -n 1 --before=”$committer_date" origin/google/testing)"
}
build() {
cd $LLVM_BUILD
ninja
}
Go for it!
checkout || exit 125
build || exit 125
run_test
The code will, for a given LLVM revision, checkout the latest revision from the google/testing branch for both clang and compiler-rt. It will then compile everything. If either fails, the script exits with code 125, which tells git bisect to skip the current commit and try another one.
Hope this helps!
Jonas