Fix defining OPENTELEMETRY_TRIVIALITY_TYPE_TRAITS

[georgthegreat]

Fixes # (issue)

Changes

Upon updating to 1.20.0 we have encountered a bunch of the following errors:

contrib/libs/opentelemetry-cpp/api/include/opentelemetry/nostd/type_traits.h:145:73: error: builtin __has_trivial_copy is deprecated; use __is_trivially_copyable instead [-Werror,-Wdeprecated-builtins]
  145 |   static constexpr bool value = std::is_copy_constructible<T>::value && __has_trivial_copy(T);

(we use clang-18 to build our code).
It turned out that some old compatibility code got broken.

@marcalff, according to README.md opentelemetry-cpp does no longer support standards below C++11, hence we can always use these type_traits from the standard library.
Can we drop the C++03 compat and simplify the things even further?

For significant contributions please make sure you have completed the following items:

• CHANGELOG.md updated for non-trivial changes

[netlify]

✅ Deploy Preview for opentelemetry-cpp-api-docs canceled.

Name	Link
🔨 Latest commit	14e036a
🔍 Latest deploy log	https://app.netlify.com/sites/opentelemetry-cpp-api-docs/deploys/67f556c01b44cd0008167db8

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.56%. Comparing base (b6908f0) to head (e081139).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3337      +/-   ##
==========================================
+ Coverage   89.55%   89.56%   +0.02%     
==========================================
  Files         210      210              
  Lines        6502     6502              
==========================================
+ Hits         5822     5823       +1     
+ Misses        680      679       -1     

see 1 file with indirect coverage changes

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[marcalff]

@georgthegreat Thanks for the PR.

Concerning the issue, we also use clang-18 in our CI, and this never broke this way.
I really would like to understand the root cause of this, could you clarify what are the values for:

• the C++ standard version used at compile time (C++11, 14, 17, ...)
• The build system used: CMake, bazel, plain makefiles, ...
• If this breaks with compiling opentelemetry-cpp itself, or when compiling an application using it
• If OPENTELEMETRY_STL_VERSION is defined in the build, and to what value
• If OPENTELEMETRY_TRIVIALITY_TYPE_TRAITS is defined (I assume it was not, please confirm)

Concerning the fix, I agree it should be simplified.
I will add review comments to make this even simpler.

[marcalff]

Thanks for the PR.

See suggestion to simplify even more.

[marcalff]

Seem also related to WITH_STL, we need to clarify whether to test __cplus_plus or OPENTELEMETRY_STL_VERSION to check for C++11.

[marcalff]

Related to:

• [BUILD] Fixes compatibility of type_traits #3274

[georgthegreat]

@marcalff, we use clang-18, -std=c++20 and -DOPENTELEMETRY_STL_VERSION=2023 (I see the divergence here but I don't see how it could lead to the issue).

I have removed OPENTELEMETRY_TRIVIALITY_TYPE_TRAITS as you suggested.

[georgthegreat]

@marcalff let's merge it.

[owent]

The fallback implementation relies on GCC's API, making it exclusive to GCC. It should be updated to support all compilers.

[georgthegreat]

Why should it? Opentelemetry does not support cxx03 standard.

[owent]

I mean the code in #else branch

[georgthegreat]

This is a dead code, opentelemetry does not support cxx03 standard / libstdc++ 5.

[marcalff]

@georgthegreat

In theory, yes, this is dead code.
In practice, no, this code is not totally dead now, there are historical reasons to maintain this part working.

What we need here is a fix that solves the trivial cases of building with recent compilers, using std:: type traits when they are available, instead of using the alternate nostd:: implementation.

The issue is probably that we need to do this independently of WITH_STL : that is, test __cplusplus instead of OPENTELEMETRY_STL_VERSION.

Now, for old cases when std:: classes are not available, like this old work around for gcc 4.8, the code needs to implement the work around as before.

[georgthegreat]

I hope I understood you correctly.

[owent]

#if !defined(OPENTELEMETRY_HAVE_STD_TYPE_TRAITS) can be removed now.

[owent]

#if !defined(OPENTELEMETRY_HAVE_STD_TYPE_TRAITS) Can be removed, but these headers are still required.

[georgthegreat]

I am done with it.
I definitely have more interesting work to do compared to supporting 12 year old compiler.