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GH-148047: Check early whether tail-calling is possible for MSVC builds on Windows (#148036)

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Rather than failing late when compiling e.g. a debug configuration
```
build.bat -c debug --tail-call-interp
```
with hundreds of
```
error C4737: Unable to perform required tail call. Performance may be degraded.
```
-- fail early with an explicit error message for configurations that are not supported by MSVC.

This is a follow-up on https://github.com/python/cpython/issues/140513 / https://github.com/python/cpython/pull/140548
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Chris Eibl 2026-04-12 07:49:18 +02:00 • committed by GitHub
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commit cbd81d59cf
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Misc/NEWS.d/next/Build/2026-04-03-20-09-46.gh-issue-148047.HE6iGK.rst Normal file
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@ -0,0 +1,2 @@
Fail fast with an explicit and clear error message if tail-calling is not
possible for MSVC builds on Windows. Patch by Chris Eibl.

9
PCbuild/pythoncore.vcxproj
View file

@ -749,4 +749,13 @@
<Target Name="_DeletePyBuildDirTxt" BeforeTargets="PrepareForBuild">
<Delete Files="$(OutDir)pybuilddir.txt" />
</Target>
<Target Name="_CheckTailCalling" BeforeTargets="PrepareForBuild" Condition="'$(UseTailCallInterp)' == 'true' and $(PlatformToolset) != 'ClangCL'">
<Error Text="MSVC supports tail-calling only for x64."
Condition="$(Platform) != 'x64'" />
<Error Text="Platform toolset >= v145 is required for tail-calling."
Condition="$(PlatformToolset.Replace('v', '0')) &lt; '145'" />
<Error Text="MSVC requires optimization to be enabled for tail-calling."
Condition="$(Configuration) == 'Debug'" />
</Target>
</Project>