[Python-Dev] introduction of attribute(deprecated) ? (original) (raw)

Stéphane Wirtel stephane at wirtel.be
Sun Mar 24 16:00:44 EDT 2019

And use an enumeration for the constants.

For example:

#include <stdio.h> #include <stdlib.h>

enum { PY_READWRITE = 0, PY_READONLY = 1,

READONLY __attribute((deprecated("use PY_READONLY"))) = PY_READONLY,
READWRITE __attribute((deprecated("use PY_READWRITE"))) = PY_READWRITE,

};

Le 24/03/19 à 20:52, Stéphane Wirtel a écrit :

Hi,

I have created the issue https://bugs.python.org/issue36347 because I wanted to add a missing macro for the PyMemberDef.flags attribute. In the Modules/*.c files, we can find descriptions with PyMemberDef where the access flag has the 0 value. Example: static PyMemberDef members[] = { {"name", TOBJECT, offsetof(MyObject, name), 0, NULL}, {NULL}, }; So, I didn't know the meaning of this magic number (0) and after a small search in structmember.h, this is the default value for an "READWRITE" attribute but there is no associated macro to this magic number. solution: add the macro for the READWRITE mode. so, my first PR has added the new macro READWRITE, like that #define READWRITE 0 and improve the documentation in Doc/c-api/structures.rst. but after a review [1], Serhiy proposed to rename it and the other ones because it did not follow the convention for names in the C API. Use a prefix for the public names, example Py or PY. I chose PY because PYWRITERESTRICTED already existed. the next steps were: * add the new macros * keep the backward-compatibility * updated the documentation I haved pushed the PR for another review so, but I don't like this definition of READONLY because there is no way to generate a warning at the compile time when we use the READONLY macro. #define PYREADONLY 0 #define READONLY PYREADONLY after that, I have closed my PR because I was not proud with my "solution".

Today, Ronald Oussoren [2] has proposed an other solution based on an enum and a new attribute, aka deprecated. I have checked with gcc and clang and this option is interesting because we generate a warning when we try to compile a code if we use the deprecated READONLY [3] In the clang documantion, the attribute(deprecated) is defined in GNU and C++11 standard, like attribute(unused). In the gcc documentation, this attribute also exists Because we already use attribute(unused) we could add attribute(deprecated). LCALL=C clang test.c -o test test.c:14:13: warning: 'READONLY' is deprecated: use PYREADONLY [-Wdeprecated-declarations] int i = READONLY; ^ test.c:8:27: note: 'READONLY' has been explicitly marked deprecated here _READONLY attribute((deprecated("use PYREADONLY"))) = PYREADONLY, ^ 1 warning generated. LCALL=C clang --version test.c -o test clang version 7.0.1 (Fedora 7.0.1-6.fc29) Target: x8664-unknown-linux-gnu Thread model: posix InstalledDir: /usr/bin ### GCC LCALL=C gcc --version test.c -o test gcc (GCC) 8.3.1 20190223 (Red Hat 8.3.1-2) Copyright (C) 2018 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. LCALL=C gcc test.c -o test test.c: In function 'main': test.c:14:5: warning: 'READONLY' is deprecated: use PYREADONLY [-Wdeprecated-declarations] int i = READONLY; ^~~ test.c:8:5: note: declared here _READONLY attribute((deprecated("use PYREADONLY"))) = PYREADONLY, ^~~~~~~~ So my question is, can we use/add attribute(deprecated) in our "development" kit? [1] https://bugs.python.org/issue36347#msg338261 [2] https://bugs.python.org/issue36347#msg338731 [3] https://bugs.python.org/issue36347#msg338745 Thank you, Stéphane

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