`make clean` errors on Windows: CreateProcess() failed

[0xEAB]

Running make clean yields an error on my Windows machine.

make[2]: Entering directory 'C:/dmd/druntime/test/betterc'
Using make SHELL "C:/Program Files/Git/usr/bin/bash.exe", should be bash.
rm -f -r ./generated/windows/debug/64
make[2]: Leaving directory 'C:/dmd/druntime/test/betterc'
C:/Tools/make.exe -C test/stdcpp MODEL=64 OS=windows BUILD=release clean
make[2]: Entering directory 'C:/dmd/druntime/test/stdcpp'
process_begin: CreateProcess(NULL, cl /nologo /EP msc_ver.c, ...) failed.
GNUmakefile.windows:5: pipe: No error
GNUmakefile.windows:6: *** non-numeric first argument to 'intcmp' function: empty value.  Stop.
make[2]: Leaving directory 'C:/dmd/druntime/test/stdcpp'
make[1]: *** [Makefile:506: test/stdcpp/.clean] Error 2
make[1]: Leaving directory 'C:/dmd/druntime'
make: *** [Makefile:79: clean] Error 2
make: Leaving directory 'C:/dmd'

Installed SDK: Visual Studio Build Tools 2022 v17.13.4

[kinke]

On Windows, the druntime tests need a cl.exe in PATH (normally by working in a 'Visual Studio Command Prompt' environment). The clean target in the top-level Makefile includes make clean invocations for all druntime test dirs, and unfortunately that means that

dmd/druntime/test/stdcpp/GNUmakefile.windows

Lines 5 to 10 in 0b29c8a

	msc_ver:=$(strip $(shell $(CC) /nologo /EP msc_ver.c))
	ifeq (1,$(intcmp $(msc_ver),1900,0,1,1))
	extra_cxxflags += /std:c++17
	extra_dflags += -extern-std=c++17
	TESTS+=string_view
	endif

is run to detect the MSVC version, although it's only required for running the actual tests and doesn't affect its clean target.

The error could be made nicer of course, checking whether cl.exe is found and bailing out early if not. But I don't know OTOH how we could eliminate the need for the set-up MSVC env.

[0xEAB]

But I do have cl.exe on my system.
It’s not in PATH but it is available – like the default install of the VS build tools does.

[kinke]

That's separate, and we won't be able to 'fix' that - some guys have dozens of cl.exe on their machines. And MSVC requires further env vars (INCLUDE, LIB, …) to work correctly. So working in a suited MSVC env to run the tests is fully expected.

The top-level clean target depending on cl.exe in PATH on the other hand is ugly indeed.

[0xEAB]

AFAICT the compiler itself is capable of figuring out where to pull cl.exe from, though.
With #21083 – all I did was to install the VS build tools and all of a sudden DMD itself would work as expected.

[kinke]

Yeah, but it's anything but trivial, and currently doesn't support arm64 for example: https://github.com/dlang/dmd/blob/master/compiler/src/dmd/vsoptions.d

[0xEAB]

I see, thanks. Indeed, that’s fair enough.