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
>