Windows tail-call CI does not run the test cases

[chris-eibl]

Excerpts from here #131526 (comment):

See e.g. https://github.com/python/cpython/actions/runs/14006628024/job/39221297660 and https://github.com/python/cpython/actions/runs/13954576580/job/39062383429#step:4:326.

After building, no more output can be seen.

This is interesting, because

cpython/.github/workflows/tail-call.yml

Lines 82 to 91 in ce79274

	- name: Native Windows (debug)
	if: runner.os == 'Windows' && matrix.architecture != 'ARM64'
	shell: cmd
	run: |
	choco install llvm --allow-downgrade --no-progress --version ${{ matrix.llvm }}.1.5
	set PlatformToolset=clangcl
	set LLVMToolsVersion=${{ matrix.llvm }}.1.5
	set LLVMInstallDir=C:\Program Files\LLVM
	./PCbuild/build.bat --tail-call-interp -d -p ${{ matrix.architecture }}
	./PCbuild/rt.bat -d -p ${{ matrix.architecture }} -q --multiprocess 0 --timeout 4500 --verbose2 --verbose3

clearly ./PCbuild/rt.bat is invoked. Maybe the reason is, because it is not used with backslashes like in

cpython/.github/workflows/reusable-windows.yml

Line 52 in ce79274

.\\PCbuild\\rt.bat

The question then is, why ./PCbuild/build.bat is working ...

Linked PRs

• GH-131678: fix Windows tail-call CI does not run the test cases #131690

[chris-eibl]

comment from @Fidget-Spinner #131526 (comment)

CI uses cmd instead if powershell, could that make a difference?

[chris-eibl]

comment from @zooba #131526 (comment)

CI uses cmd instead if powershell, could that make a difference?

It probably requires call PCbuild\build.bat ... to handle someone calling exit in the batch file. In Cmd, if the entire block is a batch file, then exit will break out of the top-level one, not the nested one, unless you use call.

[chris-eibl]

Yeah, I remember that pitfall having exit in a batch file that is not invoked via call. But then here

cpython/.github/workflows/reusable-windows.yml

Lines 41 to 56 in ce79274

	.\\PCbuild\\build.bat
	-e -d -v
	-p "${ARCH}"
	${{ fromJSON(inputs.free-threading) && '--disable-gil' || '' }}
	shell: bash
	- name: Display build info # FIXME(diegorusso): remove the `if`
	if: inputs.arch != 'arm64'
	run: .\\python.bat -m test.pythoninfo
	- name: Tests # FIXME(diegorusso): remove the `if`
	if: inputs.arch != 'arm64'
	run: >-
	.\\PCbuild\\rt.bat
	-p "${ARCH}"
	-d -q --fast-ci
	${{ fromJSON(inputs.free-threading) && '--disable-gil' || '' }}
	shell: bash

should be affected, too? But as @Fidget-Spinner noted, reusable-windows.yml uses shell: bash whereas tail-call.yml uses shell: cmd. And in a cmd prompt I definitely get an error for forward slashes.

It's still not clear for me, why ./PCbuild/build.bat is called called correctly, but as @zooba notes, there are many exits in it!

[zooba]

Those are separate run: elements. Each one of those is likely implemented by writing the contents of run: into randomly_named.bat and doing cmd /C .\randomly_named.bat, which then means any further batch files are nested within it. But because build.bat is the last one that runs, you don't notice if it exits all the way.

In the other file, there are two batch files in the same run: step, so you do notice if one exits the whole step early.

[chris-eibl]

Kudos to @zooba: prepending call fixes the issue: https://github.com/python/cpython/actions/runs/14044831663/job/39323183797?pr=131690
And reveals #131691, which I haven't noticed so far, because I only ran the full test suite for release or PGO builds ...