Add /msys64/ to msys detection for cmake tool on Windows

[Thomas1664]

I noticed that the path /msys64/ slips through when checking if the CMake binary is from msys.

Related issues: https://github.com/microsoft/vcpkg/issues?q=is%3Aissue%20state%3Aopen%20%22Command%20failed%3A%20C%3A%2Fmsys64%22

Closes microsoft/vcpkg#47171
Closes microsoft/vcpkg#46391
Closes microsoft/vcpkg#46188
Closes microsoft/vcpkg#44155
Closes microsoft/vcpkg#44154
Closes microsoft/vcpkg#47135

[dg0yt]

The original code is a very precise heuristics to detect MSYS/Cygwin environment cmake (i.e. the one which only understands POSIX paths and doesn't offer VS generators, https://packages.msys2.org/base/cmake).

What you try to detect/prevent now is cmake from the windows environment offered by msys2 (i.e. probably offering VS generators but somewhat broken around invoking RC for the Ninja generator,
https://packages.msys2.org/base/mingw-w64-cmake). This is a different problem, and the heuristics isn't significant at all, for positives and for negatives.

Not fixed by the /msys2/ heuristics:
microsoft/vcpkg#47171: Windows cmake, C:/msys64/ucrt64/bin/cmake.exe
microsoft/vcpkg#46391: Windows cmake, C:/msys64/clang64/bin/cmake.exe
microsoft/vcpkg#46188: Windows cmake, C:/msys64/ucrt64/bin/cmake.exe
microsoft/vcpkg#44155,
microsoft/vcpkg#44154: Windows cmake, C:/msys64/mingw64/bin/cmake.exe
microsoft/vcpkg#47135: Windows cmake, F:/msys64/ucrt64/bin/cmake.exe

The real common thing is that paths end in <mingw-env>/bin,
https://www.msys2.org/docs/environments/

[Thomas1664]

Not fixed by the /msys2/ heuristics:

Given that the title mentions /msys64/ and the paths also contain that string, you could have just pointed out that I had a typo in my code...

I think it's more efficient to search for /msys64/ because that requires only one comparison in contrast to 5 if I only considered the end of the path (the function is called cheap_is_acceptable after all). Furthermore, I'd consider it very likely that a cmake executable under the path /msys64/ belongs in fact to msys2.

What you try to detect/prevent now is cmake from the windows environment offered by msys2 (i.e. probably offering VS generators but somewhat broken around invoking RC for the Ninja generator,
https://packages.msys2.org/base/mingw-w64-cmake).

Judging by the comment on line 400, it's also intended to avoid using msys2's cmake.

[dg0yt]

Judging by the comment on line 400, it's also intended to avoid using msys2's cmake.

The comment says "version can't handle 'C:' in paths", but this is true only for /usr/bin/cmake.exe and /cygwin/bin/cmake.exe.
The windows environment cmakes (/ucrt64/bin/cmake.exe, /clang64/bin/cmake.exe, /mingw64/bin/cmake.exe) do handle C:.

I think it's more efficient to search for /msys64/ because that requires only one comparison in contrast to 5 if I only considered the end of the path (the function is called cheap_is_acceptable after all).

I think it is still extremely cheap to explicitly check the small set of known short strings at the end of the path.
At least in contrast to invoking the executable.

[dg0yt]

.. and path.find is a search operation, path.ends_with is a trivial comparison.

[BillyONeal]

Is there anything that distinguishes the problematic CMakes in the --version output, since we're running that to check the version already anyway.

[dg0yt]

Is there anything that distinguishes the problematic CMakes in the --version output, since we're running that to check the version already anyway.

Quick check:

Not sure if the msvc suffix is robust enough:
official (windows): cmake version 3.31.6-msvc
msys2 (ucrt64): cmake version 4.1.0

Alternatively, I can point at the generator list from cmake -G, in particular the default generator marked by *:
official (windows): * Visual Studio 17 2022 ...
msys2 (ucrt64): * Ninja ...
(msys2 (msys runtime): No Visual Studio generators!)

There is also cmake --system-information but it is slow on Windows

[BillyONeal]

Not sure if the msvc suffix is robust enough:
official (windows): cmake version 3.31.6-msvc
msys2 (ucrt64): cmake version 4.1.0

Unfortunately not:

C:\Program Files\Microsoft Visual Studio\2022\Enterprise>where cmake
C:\Program Files\CMake\bin\cmake.exe
C:\Program Files\Microsoft Visual Studio\2022\Enterprise\Common7\IDE\CommonExtensions\Microsoft\CMake\CMake\bin\cmake.exe

C:\Program Files\Microsoft Visual Studio\2022\Enterprise>cmake --version
cmake version 4.1.1

CMake suite maintained and supported by Kitware (kitware.com/cmake).

C:\Program Files\Microsoft Visual Studio\2022\Enterprise>

[dg0yt]

IMO it is sufficient and cheap to determine the parent dir of bin/cmake.exe, and to match it against the fairly stable list of msys environments (usr,mingw32,mingw64,ucrt64,clang64,clangarm64).