GeezerVison is showing github.com — Fail to build with tail cail optimization on Windows · Issue #141937 · python/cpython
Fail to build with tail cail optimization on Windows #141937DescriptionBug report
Bug description:
Building CPython with tail call optimization makes this error related to tail call optimization:
...
C:\cpython\Python\opcode_targets.h(282,38): error C2085: '_TAIL_CALL_BINARY_OP_SUBSCR_STR_INT': not in formal parameter list [C:\cpython\PCbuild\pythoncore.vcxproj]
C:\cpython\Python\opcode_targets.h(283,1): error C2061: syntax error: identifier '__attribute__' [C:\cpython\PCbuild\pythoncore.vcxproj]
C:\cpython\Python\opcode_targets.h(284,1): error C2143: syntax error: missing ')' before '(' [C:\cpython\PCbuild\pythoncore.vcxproj]
C:\cpython\Python\opcode_targets.h(284,1): error C2059: syntax error: ')' [C:\cpython\PCbuild\pythoncore.vcxproj]
C:\cpython\Python\opcode_targets.h(284,21): error C2143: syntax error: missing ')' before 'type' [C:\cpython\PCbuild\pythoncore.vcxproj]
C:\cpython\Python\opcode_targets.h(284,1): error C2091: function returns function [C:\cpython\PCbuild\pythoncore.vcxproj]
C:\cpython\Python\opcode_targets.h(284,38): error C2085: '_TAIL_CALL_BINARY_OP_SUBTRACT_FLOAT': not in formal parameter list [C:\cpython\PCbuild\pythoncore.vcxproj]
C:\cpython\Python\opcode_targets.h(285,1): error C2061: syntax error: identifier '__attribute__' [C:\cpython\PCbuild\pythoncore.vcxproj]
C:\cpython\Python\opcode_targets.h(286,1): error C2143: syntax error: missing ')' before '(' [C:\cpython\PCbuild\pythoncore.vcxproj]
C:\cpython\Python\opcode_targets.h(286,1): error C2059: syntax error: ')' [C:\cpython\PCbuild\pythoncore.vcxproj]
C:\cpython\Python\opcode_targets.h(286,21): error C2143: syntax error: missing ')' before 'type' [C:\cpython\PCbuild\pythoncore.vcxproj]
C:\cpython\Python\opcode_targets.h(286,1): error C2091: function returns function [C:\cpython\PCbuild\pythoncore.vcxproj]
C:\cpython\Python\opcode_targets.h(286,38): error C2085: '_TAIL_CALL_BINARY_SLICE': not in formal parameter list [C:\cpython\PCbuild\pythoncore.vcxproj]
C:\cpython\Python\opcode_targets.h(287,1): error C2061: syntax error: identifier '__attribute__' [C:\cpython\PCbuild\pythoncore.vcxproj]
C:\cpython\Python\opcode_targets.h(288,1): error C2143: syntax error: missing ')' before '(' [C:\cpython\PCbuild\pythoncore.vcxproj]
C:\cpython\Python\opcode_targets.h(288,1): error C2059: syntax error: ')' [C:\cpython\PCbuild\pythoncore.vcxproj]
C:\cpython\Python\opcode_targets.h(288,1): error C1003: error count exceeds 100; stopping compilation [C:\cpython\PCbuild\pythoncore.vcxproj]
While building without it works!
CPython versions tested on:
3.14
Operating systems tested on:
Windows Activitysergey-miryanov commented on Nov 25, 2025 How do you build it?
On 3.14 it fails with message: Tail calling not supported for MSVC.
On main it fails with message: You need at least VS 2026 / PlatformToolset v145 for tail calling. chris-eibl commented on Nov 25, 2025 Tail calling for MSVC is not supported in 3.14 and fails with the given error above on latest 3.14.
#139922 will implement it for 3.15.
@winapiadmin I think we can close this? winapiadmin commented on Nov 25, 2025 probably make it part of 3.14.1 (or 3.15)
MetadataMetadataDevelopmentNo branches or pull requestsIssue actions
|