Re: [PATCH] perf build: Fix broken feature check for clang due to C++ standard and changed library packaging

[Ian Rogers]

On Wed, Jul 12, 2023 at 1:35 AM Thomas Richter <tmricht@xxxxxxxxxxxxx> wrote:
>
> Perf build auto-detects features and packages already installed
> for its build. This is done in directory tools/build/feature. This
> directory contains small sample programs. When they successfully
> compile the necessary prereqs in form of libraries and header
> files are present.
>
> Such a check is also done for clang. And this check fails.
>
> Fix this and update to the latest C++ standard and use the
> new library provided by clang (which contains new packaging)
> see this link for reference:
>  https://fedoraproject.org/wiki/Changes/Stop-Shipping-Individual-Component-Libraries-In-clang-lib-Package
>
> Output before:
>  # rm -f ./test-clang.bin; make test-clang.bin; ./test-clang.bin; \
>         ll test-clang.make.output
>  g++  -MD -Wall -Werror -o test-clang.bin test-clang.cpp \
>                 > test-clang.make.output 2>&1 -std=gnu++14 \
>         -I/usr/include          \
>         -L/usr/lib64            \
>         -Wl,--start-group -lclangBasic -lclangDriver    \
>           -lclangFrontend -lclangEdit -lclangLex        \
>           -lclangAST -Wl,--end-group                    \
>         -lLLVM-16       \
>                         \
>         > test-clang.make.output 2>&1
>  make: *** [Makefile:356: test-clang.bin] Error 1
>  -bash: ./test-clang.bin: No such file or directory
>  -rw-r--r--. 1 root root 252041 Jul 12 09:56 test-clang.make.output
>  #
>
> File test-clang.make.output contains many lines of unreferenced
> symbols.
>
> Output after:
>  # rm -f ./test-clang.bin; make test-clang.bin; ./test-clang.bin; \
>         cat test-clang.make.output
>  g++  -MD -Wall -Werror -o test-clang.bin test-clang.cpp \
>          > test-clang.make.output 2>&1 -std=gnu++17     \
>         -I/usr/include          \
>         -L/usr/lib64            \
>         -Wl,--start-group -lclang-cpp -Wl,--end-group   \
>         -lLLVM-16       \
>                         \
>         > test-clang.make.output 2>&1
>  #
>
> Signed-off-by: Thomas Richter <tmricht@xxxxxxxxxxxxx>

Tested-by: Ian Rogers <irogers@xxxxxxxxxx>

Thanks!
Ian

> ---
>  tools/build/feature/Makefile | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
>
> diff --git a/tools/build/feature/Makefile b/tools/build/feature/Makefile
> index f8db69654791..0b4a6e43c5cc 100644
> --- a/tools/build/feature/Makefile
> +++ b/tools/build/feature/Makefile
> @@ -353,12 +353,10 @@ $(OUTPUT)test-llvm-version.bin:
>                 > $(@:.bin=.make.output) 2>&1
>
>  $(OUTPUT)test-clang.bin:
> -       $(BUILDXX) -std=gnu++14                                 \
> +       $(BUILDXX) -std=gnu++17                                 \
>                 -I$(shell $(LLVM_CONFIG) --includedir)          \
>                 -L$(shell $(LLVM_CONFIG) --libdir)              \
> -               -Wl,--start-group -lclangBasic -lclangDriver    \
> -                 -lclangFrontend -lclangEdit -lclangLex        \
> -                 -lclangAST -Wl,--end-group                    \
> +               -Wl,--start-group -lclang-cpp -Wl,--end-group   \
>                 $(shell $(LLVM_CONFIG) --libs Core option)      \
>                 $(shell $(LLVM_CONFIG) --system-libs)           \
>                 > $(@:.bin=.make.output) 2>&1
> --
> 2.41.0
>