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Diffstat (limited to 'compiler_wrapper/README.md')
| -rw-r--r-- | compiler_wrapper/README.md | 32 |
1 files changed, 30 insertions, 2 deletions
diff --git a/compiler_wrapper/README.md b/compiler_wrapper/README.md index 12ae3131..bb63798a 100644 --- a/compiler_wrapper/README.md +++ b/compiler_wrapper/README.md @@ -7,7 +7,7 @@ Build is split into 2 steps via separate commands: - build: builds the actual go binary, assuming it is executed from the folder created by `bundle.py`. -This allows to copy the sources to a Chrome OS / Android +This allows to copy the sources to a ChromeOS / Android package, including the build script, and then build from there without a dependency on toolchain-utils itself. @@ -24,7 +24,7 @@ Run `install_compiler_wrapper.sh` to install the new wrapper in the chroot: Then perform the tests, e.g. build with the new compiler. -## Updating the Wrapper for Chrome OS +## Updating the Wrapper for ChromeOS To update the wrapper for everyone, the new wrapper configuration must be copied into chromiumos-overlay, and new revisions of the gcc and llvm ebuilds must be @@ -73,3 +73,31 @@ Generated wrappers are stored here: `/usr/bin/clang_host_wrapper` - Gcc host wrapper: `/usr/x86_64-pc-linux-gnu/gcc-bin/10.2.0/host_wrapper` + +## Using the compiler wrapper to crash arbitrary compilations + +When Clang crashes, its output can be extremely useful. Often, it will provide +the user with a stack trace, and messages like: + +``` +clang-15: unable to execute command: Illegal instruction +clang-15: note: diagnostic msg: /tmp/clang_crash_diagnostics/foo-5420d2.c +clang-15: note: diagnostic msg: /tmp/clang_crash_diagnostics/foo-5420d2.sh +``` + +Where the artifacts at `/tmp/clang_crash_diagnostics/foo-*` are a full, +self-contained reproducer of the inputs that caused the crash in question. +Often, such a reproducer is very valuable to have even for cases where a crash +_doesn't_ happen (e.g., maybe Clang is now emitting an error where it used to +not do so, and we want to bisect upstream LLVM with that info). Normally, +collecting and crafting such a reproducer is a multi-step process, and can be +error-prone; compile commands may rely on env vars, they may be done within +`chroot`s, they may rely on being executed in a particular directory, they may +rely on intermediate state, etc. + +Because of the usefulness of these crash reports, our wrapper supports crashing +Clang even on files that ordinarily don't cause Clang to crash. For various +reasons (b/236736327), this support currently requires rebuilding and +redeploying the wrapper in order to work. That said, this could be a valuable +tool for devs interested in creating a self-contained reproducer without having +to manually reproduce the environment in which a particular build was performed. |