Re: [PATCH 0/9] perf build: Fix builds with clang and BUILD_NONDISTRO

[Namhyung Kim <namhyung@kernel.org>]

On Tue, Sep 15, 2026 at 11:12:09PM -0700, Ian Rogers wrote:
> Several perf build configurations are broken, and stayed broken because
> the build test suite doesn't cover them.
> 
> Three of them fail outright:
> 
>   $ make CC=clang BUILD_NONDISTRO=1
>   util/libbfd.c:56:1: error: mutex 'bfd_mutex' is still held at the end
>   of function [-Werror,-Wthread-safety-analysis]
> 
>   $ make BUILD_NONDISTRO=1 NO_DEMANGLE=1
>   util/symbol.c:2714: error: 'DMGL_PARAMS' undeclared
> 
>   $ make CC=clang-19
>   *** Specify CROSS_COMPILE or add CLANG_TARGET_FLAGS for x86_64
> 
> A fourth is worse for being silent. "make CC=clang" appends clang's
> --target= and -fintegrated-as to CXX, but CXX is only set to clang++ by
> "make LLVM=1", so it is still g++ and rejects both. Feature tests are
> allowed to fail, so nothing is reported: the build succeeds and just
> quietly drops libllvm and C++ demangling support.
> 
>   $ make CC=clang && grep LIBLLVM .config-detected
>   (nothing, whereas a gcc build reports CONFIG_LIBLLVM=y)
> 
> The patches are grouped as:
> 
>   1-2  Fix the two build failures, in libbfd.c and symbol.c.
>   3-4  Include the headers that are used directly rather than relying
>        on other headers to drag them in. No functional change.
>   5-7  Fix the clang handling in Makefile.config: don't give clang's
>        flags to a non-clang CXX, and use the CC that was asked for
>        instead of hard coding "clang" when picking the target triple
>        and when testing the compiler version.
>   8    Remove three build test entries left behind by the removal of
>        the options they tested. None of them define what to build, so
>        each silently repeats "make_pure" and the suite spends six
>        builds appearing to cover options that no longer exist.
>   9    Add build tests for the configurations above, so they don't
>        break again. As a build that loses a feature still succeeds,
>        the clang tests also check that libLLVM is still built in.
> 
> Testing:
> 
>  - 13 build configurations (gcc, clang, versioned clang, LLVM=1,
>    BUILD_NONDISTRO, NO_DEMANGLE, NO_LIBDW, NO_LIBELF, DEBUG, asan,
>    refcount checking) pass, where two failed before the series.
>  - Every patch builds on its own, so the series stays bisectable.
>  - Each fix was confirmed by reintroducing the bug and checking that
>    the test added in patch 9 fails:
> 
>      CXX flags given to g++     make_clang             fails on libLLVM
>      libbfd thread safety       make_clang_nondistro   fails to compile
>      symbol.c demangling        make_nondistro_no_demangle  likewise
> 
> Ian Rogers (9):
>   perf libbfd: Fix the clang -Wthread-safety build failure
>   perf symbol: Fix the build when demangling with libbfd
>   perf libbfd: Include the headers that are used
>   perf pmu: Include the headers that are used
>   perf build: Only pass clang flags to CXX when CXX is clang
>   perf build: Use the given CC rather than clang in clang builds
>   perf build: Check the version of the compiler that is used
>   perf build: Remove leftovers of removed build options
>   perf test: Add build tests for clang and libbfd demangling

Acked-by: Namhyung Kim <namhyung@kernel.org>

Thanks,
Namhyung

> 
>  tools/perf/Makefile.config | 13 +++++++---
>  tools/perf/Makefile.perf   |  3 ---
>  tools/perf/tests/make      | 50 ++++++++++++++++++++++++++++++++++----
>  tools/perf/util/Build      |  2 +-
>  tools/perf/util/libbfd.c   | 41 ++++++++++++++++++++++++++-----
>  tools/perf/util/libbfd.h   |  9 +++++++
>  tools/perf/util/pmu.c      |  5 +++-
>  tools/perf/util/symbol.c   | 18 +++++++++++---
>  8 files changed, 119 insertions(+), 22 deletions(-)
> 
> 
> base-commit: 91b0782fc9e9d2f0a40b5256146e014802fdbb36
> -- 
> 2.55.0.1032.g73a4cd73de-goog
>