Document WITH_STL=ON in details

[marcalff]

Build failure on macos12-arm-64bit when using WITH_STL=ON

Darwin Kernel Version 21.1.0
-- The C compiler identification is AppleClang 13.0.0.13000029
-- The CXX compiler identification is AppleClang 13.0.0.13000029

Build failure:

/.../opentelemetry-cpp/opentelemetry-cpp-1.6.1/api/include/opentelemetry/std/utility.h:63:34: error: no template named 'make_index_sequence' in namespace 'std'
using make_index_sequence = std::make_index_sequence<N>;
                            ~~~~~^
/.../opentelemetry-cpp/opentelemetry-cpp-1.6.1/api/include/opentelemetry/std/utility.h:66:29: error: no template named 'index_sequence' in namespace 'std'
using index_sequence = std::index_sequence<Ints...>;
                       ~~~~~^

The issue is that WITH_STL is too broad, it assumes that:

• std::unique_ptr is available (yes)
• std::shared_ptr is available (yes)
• std::make_index_sequence is available (no)

Please consider to:

• either split HAVE_CPP_STDLIB into more granular defines
• or make checks in CMakeList.txt to make sure WITH_STL can actually be used, that is std class used actually exists.

Invalid configurations, if WITH_STL is considered invalid on macos12, should be detected at configure (CMake) time, not later at compile time.

Please document expected usage and limitations of WITH_STL, in INSTALL.md

[lalitb]

related issue: #1071 . Also, we are missing clang build for CI with WITH_STL enabled.

Need to see more details, but is this some bug in the clang compiler if the std::make_index_sequence is missing ?

[marcalff]

related issue: #1071 . Also, we are missing clang build for CI with WITH_STL enabled.

Need to see more details, but is this some bug in the clang compiler if the std::make_index_sequence is missing ?

Yes, I am aware of #1071. Not sure if find grained options are needed, this is a separate discussion.

CI build cmake.c++20.stl.test is using WITH_STL.

For this macos build, I need to investigate details, it could be a C++11/14/17/20 issue as well.

[marcalff]

Closing as a duplicate of #1071.

To be usefull, WITH_STL needs to be broken down at the minimum by versions of the STL, otherwise it is impossible to use a C++11 feature unless a C++20 STL is available.