--without-tail-call-interp actually enables the tail-call interpreter, instead of disabling!

In configure.ac, if the user passes --tail-call-interp in the negative, we set Py_TAIL_CALL_INTERP to 0:

Lines 7027 to 7032 in 1feaecc

    
           if test "$withval" = no 
        
           then 
        
             AC_DEFINE([Py_TAIL_CALL_INTERP], [0], 
        
             [Define if you want to use tail-calling interpreters in CPython.]) 
        
             AC_MSG_RESULT([no]) 
        
           fi

However, in ceval_macros.h and bytecodes.c, we check for #ifdef Py_TAIL_CALL_INTERP and #if defined(Py_TAIL_CALL_INTERP), for instance:

cpython/Python/ceval_macros.h

Line 76 in 1feaecc

#ifdef Py_TAIL_CALL_INTERP

)

Thus, defining the macro -- even with a value of 0 -- actually enables the feature! I think the consistent behavior (consistent with USE_COMPUTED_GOTOS) is probably to switch the preprocessor guards to #if, instead of #ifdef.

Linked PRs

Great catch! Will fix this.

gh-129989: Properly disable tailcall interp in configure (GH-129991)

Should be fixed. Please do let us know if there are any further issues.

gh-129989: Change Py_TAIL_CALL_INTERP ifndef to ! (#130269)

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`--without-tail-call-interp` actually enables the tail-call interpreter, instead of disabling! #129989

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	if test "$withval" = no
	then
	AC_DEFINE([Py_TAIL_CALL_INTERP], [0],
	[Define if you want to use tail-calling interpreters in CPython.])
	AC_MSG_RESULT([no])
	fi

--without-tail-call-interp actually enables the tail-call interpreter, instead of disabling! #129989

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Fidget-Spinner commented on Feb 11, 2025

Fidget-Spinner commented on Feb 16, 2025

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`--without-tail-call-interp` actually enables the tail-call interpreter, instead of disabling! #129989