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winreg.ExpandEnvironmentStrings() passes the buffer size as the error code on failure #161021

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winreg.ExpandEnvironmentStrings() passes the buffer size as the error code on failure#161021
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OS-windowstype-bugAn unexpected behavior, bug, or error

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@aisk
aisk
opened on Oct 31, 2026

cpython/PC/winreg.c

Lines 1265 to 1266 in 2468c35

return PyErr_SetFromWindowsErrWithFunction(retValueSize,
"ExpandEnvironmentStrings");

retValueSize is the required buffer size returned by the first ExpandEnvironmentStringsW() call, but it is passed as the error code here, which raises an exception with a misleading error number.

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  1. aisk
    added
    type-bugAn unexpected behavior, bug, or error
    OS-windows
    on Oct 31, 2026
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    OS-windowstype-bugAn unexpected behavior, bug, or error

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