Specialize Py_DECREF() for Py_REF_DEBUG#16781
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Simplify Py_DECREF() code for release mode: don't pass __FILE__ and __LINE__ to the static inline function.
vstinner commented Oct 14, 2019
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. |
serhiy-storchaka commented Oct 14, 2019
Why so complicated? Why not use just macros? |
Oh, see https://bugs.python.org/issue35059#msg328367 for the rationale. |
| _Py_NegativeRefcount(filename, lineno, op); | ||
| } | ||
| #endif | ||
| _Py_RefTotal--; |
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So this _Py_DEC_REFTOTAL would be converted in your plan?
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_Py_DEC_REFTOTAL = _Py_RefTotal-- when Py_REF_DEBUG is defined. I prefer to put directly the real code, it may help debugging. It avoids the indirection of the preprocessor.
ghost commented Oct 18, 2019
I tested almost all versions of gcc/clang/msvc/icc: All versions have the same behavior: |
vstinner commented Dec 10, 2019
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.) |
| #endif | ||
| _Py_RefTotal--; | ||
| if (--op->ob_refcnt == 0){ | ||
| _Py_Dealloc(op); |
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This code dupe irks me. Can't you make the REF_DEBUG version call the regular version instead?
vstinner commented Jan 6, 2020
_Py_DECREF() function cannot use I wrote PR #17870 to avoid duplicated code and avoid passing |
vstinner commented Jan 25, 2020
6 participants
Simplify Py_DECREF() code for release mode: don't pass FILE and
LINE to the static inline function.