Use implementation independent attributes

[0xAltCunningham]

Fixes #285.

[codecov-commenter]

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@@            Coverage Diff            @@
##            master      #284   +/-   ##
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  Coverage   100.00%   100.00%           
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  Files           10        10           
  Lines         1951      1951           
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Flag	Coverage Δ
32bit	100.00% <ø> (ø)
gcc	99.48% <ø> (ø)

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Impacted Files	Coverage Δ
include/intx/intx.hpp	100.00% <ø> (ø)

[axic]

We run four MSVC compiler versions (see recent builds here and they seem to succeed.

What compiler version do you see this problem with? Can you point us to some logs / repository?

[0xAltCunningham]

I'm seeing this problem with MSVC 19.34.31942.0 (MSBuild v17.4.1+9a89d02ff).
It's the current version used in GitHub Actions when the windows-latest image is selected.
Here's an example of the warning being thrown in a build run:
https://github.com/0xAltCunningham/evmtools/actions/runs/4076238955/jobs/7271225492#step:5:19

[0xAltCunningham]

I got the compiler version wrong on my previous comment, that was just the MSBuild version.

When rerunning the job I realized the compiler version is actually MSVC 19.34.31942.0:

-- Building for: Visual Studio 17 2022
-- The CXX compiler identification is MSVC 19.34.31942.0

[0xAltCunningham]

Not sure if related, but something else that I think could be the cause of this warning is that I'm using CXX_STANDARD 23 when building my project.

[axic]

Interesting, we do have an MSVC 2022 build. Will need to wait for @chfast, maybe he has some insight.

[axic]

@chfast ping

[chfast]

We specifically disable this warning because the idea of C++ attributes is to wrap compiler-specific features (so it is expected some attributes are going to be unknown to some compilers). Otherwise, you end up with #if hell.
https://github.com/chfast/intx/blob/master/cmake/CableCompilerSettings.cmake#L135-L136

[chfast]

This has been fixed by #286. Let me know if this works for you.

[0xAltCunningham]

Hey @chfast, the changes introduced in #286 work for me (Windows CI run)! Thanks for taking the time to fix it, and I understand now that adding #ifs to the functions would be a messy solution.

Thanks @axic as well, for the prompt responses and attention paid to this issue.

[chfast]

I understand now that adding #ifs to the functions would be a messy solution

I think for intx.hpp this is acceptable. After the change the file should build without any warnings disabled. For intx/test I decided to disable unknown pragma warnings but this should affect users much less.

[chfast]

I will make intx release soon.