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

[Ian Rogers]

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

 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