To:     irogers@google.com
Cc:     acme@kernel.org, alexander.shishkin@linux.intel.com,
        daniel@iogearbox.net, jolsa@redhat.com, leo.yan@linaro.org,
        linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org,
        llvm@lists.linux.dev, mark.rutland@arm.com, mingo@redhat.com,
        mpetlan@redhat.com, namhyung@kernel.org, nathan@kernel.org,
        ndesaulniers@google.com, peterz@infradead.org,
        sedat.dilek@gmail.com, philip.li@intel.com
From:   Ma Xinjian <xinjianx.ma@intel.com>
Subject: Re: [PATCH 2/2] perf clang: Fixes for more recent LLVM/clang
Message-ID: <1fcb636d-71ab-12e8-aa7f-c7ca4f89a5ed@intel.com>
Date:   Fri, 12 Nov 2021 18:24:44 +0800
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Hi

We build perf with clang also recently, but unlucky that failed with 
following errors:


```
In file included from /usr/lib/llvm-7/include/llvm/ADT/STLExtras.h:21,
                  from /usr/lib/llvm-7/include/llvm/ADT/StringRef.h:13,
                  from /usr/lib/llvm-7/include/clang/Basic/Version.h:20,
                  from test-clang.cpp:2:
/usr/lib/llvm-7/include/llvm/ADT/SmallVector.h: In instantiation of 
'void llvm::SmallVectorTemplateBase<T, true>::push_back(const T&) [with 
T = clang::driver::OffloadUnbundlingJobAction::DependentActionInfo]':
/usr/lib/llvm-7/include/clang/Driver/Action.h:579:61:   required from here
/usr/lib/llvm-7/include/llvm/ADT/SmallVector.h:313:11: error: 'void* 
memcpy(void*, const void*, size_t)' writing to an object of type 'struct 
clang::driver::OffloadUnbundlingJobAction::DependentActionInfo' with no 
trivial copy-assignment; use copy-initialization instead 
[-Werror=class-memaccess]
      memcpy(this->end(), &Elt, sizeof(T));
      ~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from /usr/lib/llvm-7/include/clang/Driver/Driver.h:15,
                  from test-clang.cpp:6:
/usr/lib/llvm-7/include/clang/Driver/Action.h:549:10: note: 'struct 
clang::driver::OffloadUnbundlingJobAction::DependentActionInfo' declared 
here
    struct DependentActionInfo final {
           ^~~~~~~~~~~~~~~~~~~
cc1plus: all warnings being treated as errors
```

llvm version: 7
rootfs: Debian10
kernel: v5.8 v5.11 v5.15
reproduce:
$ cd linux/tools/perf
$ make LIBCLANGLLVM=1 ARCH= EXTRA_CFLAGS='-fno-omit-frame-pointer 
-fsanitize=undefined -fsanitize=address'

Would you please kindly point out what's wrong with our steps? Or can 
you give us your command to make perf with clang?


Thanks
Ma Xinjian