Does this repo change the default of -std=c++<...> for clang++?
I am trying to transition to the clang++ + hip::device target logic (#2275) with ECP AMReX & ECP WarpX.

The compiler identifies as Clang 12 but it builds by default in C++11.

My targets set

target_compile_features(${tgt} PUBLIC cxx_std_14)

and only with this clang++ in hip 4.1.0 I see no flags getting added to the command line.

Note that Clang 6+ already default to C++14: https://gist.github.com/ax3l/53db9fa8a4f4c21ecc5c4100c0d93c94

But -xhip does not it seems:

rocm-4.1.0/llvm/bin/clang++ -dM -E -xhip  /dev/null | grep -F __cplusplus
#define __cplusplus 201103L
#define __cplusplus 201103L

Vs.:

rocm-4.1.0/llvm/bin/clang++ -dM -E -x c++  /dev/null | grep -F __cplusplus
#define __cplusplus 201402L

My Workaround

export CXXFLAGS="-std=c++14"

before all CMake builds, because the target compile feature cxx_std_14 is currently ignored for -xhip objects.

Alternative work-around: CXX_STANDARD always adds -std=c++XX, even if the compiler default fulfills it

set_property(TARGET mytarget PROPERTY CXX_STANDARD 14)

The reason for that is that cxx_std_14 asks for feature support (at least a minimal version) while CXX_STANDARD is an exact request for a version.