ExternalProgram: Ensure that the path has no forward slashes on Windows

[lb90]

Some programs like cmd.exe do not expect forward slashes in the first part of GetCommandLineW() (the part corresponding to argv[0]) and confuse the slash for a command-line switch.

This is a fix for test cases\common\33 run program. Also helps #1526

Note: shutil.which uses forward slash also on Windows. We may introduce a mesonlib.which() helper (see also commit 935aa452)

https://github.com/python/cpython/blob/v3.13.0/Lib/shutil.py#L1503

[eli-schwartz]

This is a fix for test cases\common\33 run program. Also helps #1526

I don't see how this helps #1526 since it actually does the exact opposite of what was proposed there? The issue is that meson globally replaces command lines in ninja using the opposite of what you do here, in order to solve quoting hell on Windows. The solution is to only do it ("the opposite of this PR") for filepaths, including ExternalProgram.

Anything you do in this PR will get reverted again by the global replacement in ninjabackend, so this PR only has an effect on commands run at configure time.

[lb90]

Hi @eli-schwartz!

I don't see how this helps #1526 since it actually does the exact opposite of what was proposed there? The issue is that meson globally replaces command lines in ninja using the opposite of what you do here, in order to solve quoting hell on Windows. The solution is to only do it ("the opposite of this PR") for filepaths, including ExternalProgram.

Thanks, I admit that I don't know much about the internals of Meson, so that's very helpful! 🙂 anyway, isn't #1526 about using backward slashes \ for program and file paths? It mentions cmd.exe, which AFAIK has problems when invoked as C:/Windows/System32/cmd.exe, but not C:\Windows\System32\cmd.exe

Anything you do in this PR will get reverted again by the global replacement in ninjabackend, so this PR only has an effect on commands run at configure time.

Yes, indeed the test fails during configure time. The path will be reverted to forward slashes / when writing the ninja build rules, but probably that's an issue that can be tackled separately from this

[eli-schwartz]

Thanks, I admit that I don't know much about the internals of Meson, so that's very helpful! 🙂 anyway, isn't #1526 about using backward slashes \ for program and file paths? It mentions cmd.exe, which AFAIK has problems when invoked as C:/Windows/System32/cmd.exe, but not C:\Windows\System32\cmd.exe

No, it's about using forward slashes / for programs and file paths, and ceasing meson's current, highly unfortunate, violation of user-supplied arguments such as sed s/@PREFIX@/\/usr/ becoming sed s/@PREFIX@///usr/.

See:
#737
#12097
#13172
#4393

The ticket is badly worded since we currently do "normalize" them everywhere, except for the one place we pass filenames (not commands!) to cmd.exe

[lb90]

This has been fixed by #13886 it seems, closing!