In Python 3.7, Py_DECREF() was a macro. I converted it to a static inline function in PR #10079 of https://bugs.python.org/issue35059 The new static inline function always require filename and lineno arguments, even in release mode. I'm not sure that all compilers are smart enough to remove the arguments, so I prefer to help compilers to ensure that the emited machine code is as efficient as Python 3.7.

Why so complicated? Why not use just macros?

Why so complicated? Why not use just macros?

Oh, see https://bugs.python.org/issue35059#msg328367 for the rationale.

I'm not sure that all compilers are smart enough to remove the arguments

I tested almost all versions of gcc/clang/msvc/icc:
https://godbolt.org/z/w-N-Kt

All versions have the same behavior:
If with -O1 option, compilers are smart enough to remove the arguments.
If without any option, the extra machine code was emited.

Why not use just macros?

Static inline functions have multiple benefits over macros. Let me give you one example.

Today we get a bug report on Fedora on Python 3.8 which uses static inline functions rather than macros. Thanks to that, the line number in the gdb traceback was more accurate and so more usefull. (Sadly, the bug report is private because it's an automated crash report and it might contain sensitive information, so I cannot share it.)

This code dupe irks me. Can't you make the REF_DEBUG version call the regular version instead?

_Py_DECREF() function cannot use __FILE__ and __LINE__ preprocessor magic macros. Only a macro can use them.

I wrote PR #17870 to avoid duplicated code and avoid passing __FILE__ and __LINE__ in release mode (when Py_REF_DEBUG is not set).

I merged PR #17870 instead, commit f3a0a6b.