Messages in this thread | | | From | Nick Desaulniers <> | Date | Fri, 12 Mar 2021 14:05:02 -0800 | Subject | Re: [PATCH] gcov: fix clang-11+ support |
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On Fri, Mar 12, 2021 at 12:25 PM 'Fangrui Song' via Clang Built Linux <clang-built-linux@googlegroups.com> wrote: > > function_name can be unconditionally deleted. It is not used by llvm-cov > gcov. You'll need to delete a few assignments to gcov_info_free but you > can then unify the gcov_fn_info_dup and gcov_info_free implementations. > > LG. On big-endian systems, clang < 11 emitted .gcno/.gcda files do not > work with llvm-cov gcov < 11. To fix it and make .gcno/.gcda work with > gcc gcov I chose to break compatibility (and make all the breaking > changes like deleting some CC1 options) in a short window. At that time > I was not aware that there is the kernel implementation. Later on I was > CCed on a few https://github.com/ClangBuiltLinux/linux/ gcov issues but > I forgot to mention the interface change.
These are all good suggestions. Since in v2 I'll drop support for clang < 11, I will skip additional patches to disable GCOV when using older clang for BE, and the function_name cleanup.
> Now in clang 11 onward, clang --coverage defaults to the gcov 4.8 > compatible format. You can specify the CC1 option (internal option, > subject to change) -coverage-version to make it compatible with other > versions' gcov. > > -Xclang -coverage-version='407*' => 4.7 > -Xclang -coverage-version='704*' => 7.4 > -Xclang -coverage-version='B02*' => 10.2 (('B'-'A')*10 = 10)
How come LLVM doesn't default to 10.2 format, if it can optionally produce it? We might be able to reuse more code in the kernel between the two impelementations, though I expect the symbols the runtime is expected to provide will still differ. Seeing the `B` in `B02*` is also curious.
Thanks for the review, will include your tag in v2. -- Thanks, ~Nick Desaulniers
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