support clang-cl

[miyanyan]

the same changes as maths

[miyanyan]

I got the constexpr steps related error:

[build] C:\PROGRA~1\MICROS~1\2022\COMMUN~1\VC\Tools\Llvm\x64\bin\clang-cl.exe  /nologo -TP -DH5_BUILT_AS_DYNAMIC_LIB -ID:\github\miyanyan\mathplot -ID:\github\miyanyan\vcpkg\installed\x64-windows\include -ID:\github\miyanyan\mathplot\maths -ID:\github\miyanyan\mathplot\include\rapidxml-1.13 -DNOMINMAX /EHsc /Zc:__cplusplus /constexpr:steps500000000 -DMPLOT_HAVE_STD_FORMAT -Xclang -fopenmp -DMPLOT_FONTS_DIR="\"D:/github/miyanyan/mathplot/fonts\""  /MD /O2 /Ob2 /DNDEBUG -std:c++20 /showIncludes /Foexamples\CMakeFiles\testce.dir\testce.cpp.obj /Fdexamples\CMakeFiles\testce.dir\ -c -- D:\github\miyanyan\mathplot\examples\testce.cpp
[build] clang-cl: warning: argument unused during compilation: '/constexpr:steps500000000' [-Wunused-command-line-argument]
[build] D:\github\miyanyan\mathplot\examples\testce.cpp(12,10): error: constexpr variable 'geo' must be initialized by a constant expression
[build]    12 |     auto geo = sm::geometry_ce::make_icosahedral_geodesic<double, 3>();
[build]       |          ^     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
[build] C:\Program Files\Microsoft Visual Studio\2022\Community\VC\Tools\MSVC\14.44.35207\include\limits(916,59): note: constexpr evaluation hit maximum step limit; possible infinite loop?
[build]   916 |     _NODISCARD static constexpr double epsilon() noexcept {
[build]       |                                                           ^
[build] D:\github\miyanyan\vcpkg\installed\x64-windows\include\sm/geometry(195,82): note: in call to 'epsilon()'
[build]   195 |                     if (sm::cem::abs(geo.poly.vertices[v][0] - vb[0]) < thresh * std::numeric_limits<F>::epsilon()
[build]       |                                                                                  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
[build] D:\github\miyanyan\mathplot\examples\testce.cpp(12,16): note: in call to 'make_icosahedral_geodesic<double, 3>()'
[build]    12 |     auto geo = sm::geometry_ce::make_icosahedral_geodesic<double, 3>();
[build]       |                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
[build] 1 error generated.

[sebsjames]

Ok, so I'm not surprised you got the constpexr:steps problem, because there are tests and examples which compile constexpr functions that need more steps than the usual default. Given that clang-cl seems to be unable to set the constexpr steps like normal clang, gcc and normal visual code are able to, then you could instead conditionally disable the compilation of those tests/examples.

[sebsjames]

OR there may be a solution!

Try adding this for clang-cl:

-Xclang -fconstexpr-steps -Xclang 500000000

OR maybe this:

/clang:-fconstexpr-steps=500000000

both of which I found suggested here: https://stackoverflow.com/questions/41010768/clang-cl-exe-and-constexpr-depth

[miyanyan]

OR there may be a solution!

Try adding this for clang-cl:

-Xclang -fconstexpr-steps -Xclang 500000000

OR maybe this:

/clang:-fconstexpr-steps=500000000

both of which I found suggested here: https://stackoverflow.com/questions/41010768/clang-cl-exe-and-constexpr-depth

worked!