[llvm-dev] llvm-config --cxxflags should report C++ language standard version

Saleem Abdulrasool via llvm-dev llvm-dev at lists.llvm.org
Wed Oct 30 19:46:26 PDT 2019

On Wed, Oct 30, 2019 at 4:17 PM Johan Engelen <jbc.engelen at gmail.com> wrote:

> Hi all,
>   Since  2724d9e12960cc1d93eeabbfc9aa1bffffa041cc, llvm-config -cxxflags
> no longer reports the C++ language standard version (e.g. "-std=c++14")
> used to compile LLVM. This may break builds of projects that build with the
> same flags as LLVM, e.g. the LDC compiler.
> Quoting from llvm/tools/llvm-config/CMakeLists.txt:
> ```
> # The language standard potentially affects the ABI/API of LLVM, so we want
> # to make sure it is reported by llvm-config.
> ```
> Even in the case of default C++ version, in my opinion llvm-config should
> explicitly report it.

I will add an option to report the C++ version, though that would be a new
option and require reworking the consumers to be aware of that.  It would
be better to actually rely on CMake to provide the details of the build
rather than `llvm-config`.

> cheers,
>   Johan

Saleem Abdulrasool
compnerd (at) compnerd (dot) org
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