[issue18090] dict_contains first argument declared register, and shouldn't be
Larry Hastings added the comment: Closed as this is a subset of #18722. -- resolution: - fixed stage: needs patch - committed/rejected status: open - closed ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue18090 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue18090] dict_contains first argument declared register, and shouldn't be
Terry J. Reedy added the comment: Guido, do you still believe in using 'register' in C code in general or in particular, for function arguments. Many of the uses in dictobject.c go back to your rev1256 and rev5396. The one that caught Larry's eye for dict_contains appears to be from the latter. (Many other appearances are credited to Antoine as solipsis, though these may be from merges or something, and he has already said he thinks they could go.) -- nosy: +gvanrossum, terry.reedy ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue18090 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue18090] dict_contains first argument declared register, and shouldn't be
Changes by Arfrever Frehtes Taifersar Arahesis arfrever@gmail.com: -- nosy: +Arfrever ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue18090 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue18090] dict_contains first argument declared register, and shouldn't be
Larry Hastings added the comment: I poked around in a draft of the next ANSI C standard dated April 12 2011. They don't have much to say about the semantics of register. The definition is found in 6.7.1.6: A declaration of an identifier for an object with storage-class specifier register suggests that access to the object be as fast as possible. In a footnote they say you can't take the address of something declared register. In 6.7.6.3.2 they explicitly allow using register as part of the specification of a function parameter. However, in 6.9.2 they say register cannot appear as part of an external declaration, including those for functions. 6.9.2 is where I stake my claim. If register is irrelevant to calling convention, then why would the C standard preclude using it in an external declaration? If it had no effect on the call they wouldn't care. Therefore, declaring a parameter as register affects its calling convention. (Or, it would, if register actually did anything). Therefore casting a function from using register to not using register is a bug. Therefore we shouldn't do it. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue18090 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue18090] dict_contains first argument declared register, and shouldn't be
Stefan Krah added the comment:
+1 for removing all occurrences of register.
Regarding the grammar, we have:
function-definition:
declaration-specifiers-opt declarator declaration-list-opt
compound-statement
So I think that part of an external declaration refers to the outermost
declaration-specifiers, not to some inner declaration-specifiers that are
part of the parameter-type-list. Otherwise it would also be forbidden to
use register in the compound-statement. ;)
Thus, IMO this is legal:
a) int f (register int x) {return x;}
But this is not allowed:
b) register int f (int x) {return x;}
As Mark said, a) does not alter the calling convention. It's just a request
to keep x in a register in the function body once the parameter passing is
done.
--
nosy: +skrah
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[issue18090] dict_contains first argument declared register, and shouldn't be
Amaury Forgeot d'Arc added the comment: If register is irrelevant to calling convention, then why would the C standard preclude using it in an external declaration? Maybe here external is the opposite of static: register is OK in a single translation unit (where the calling convention does not really matter), but not allowed between multiple .c files (which register, anyway?) +1 for removing it. -- nosy: +amaury.forgeotdarc ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue18090 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue18090] dict_contains first argument declared register, and shouldn't be
Larry Hastings added the comment: Having re-read the spec a couple times, I am now thoroughly confused and don't know what to think. Certainly I now believe I was previously misinterpreting aspects of the spec. I still think removing register from the parameter lists of external functions is a good idea. But smart people work on CPython, particularly on dictobject.c, so I find it easy to believe I'm missing something. If having it there is actually a good idea I'd love to learn why! -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue18090 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue18090] dict_contains first argument declared register, and shouldn't be
Changes by Ezio Melotti ezio.melo...@gmail.com: -- nosy: +ezio.melotti ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue18090 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue18090] dict_contains first argument declared register, and shouldn't be
Mark Dickinson added the comment: +1 for removing all occurrences of register. Seconded. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue18090 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue18090] dict_contains first argument declared register, and shouldn't be
Changes by Larry Hastings la...@hastings.org: -- nosy: +Mark.Shannon, rhettinger ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue18090 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue18090] dict_contains first argument declared register, and shouldn't be
Antoine Pitrou added the comment: I would recommend suppressing all register keywords from our C source files. It shouldn't make any difference these days. -- nosy: +pitrou ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue18090 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue18090] dict_contains first argument declared register, and shouldn't be
Changes by Antoine Pitrou pit...@free.fr: -- nosy: +serhiy.storchaka ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue18090 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue18090] dict_contains first argument declared register, and shouldn't be
Changes by Serhiy Storchaka storch...@gmail.com: -- nosy: +mark.dickinson ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue18090 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue18090] dict_contains first argument declared register, and shouldn't be
Mark Shannon added the comment: The register qualifier on the parameter does not alter the calling convention, it determines the storage class of the parameter variable within the function. Having said that I am all in favour in removing any and all register declarations. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue18090 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue18090] dict_contains first argument declared register, and shouldn't be
Larry Hastings added the comment: The register qualifier on the parameter does not alter the calling convention, it determines the storage class of the parameter variable within the function. You assert that declaring a parameter as register instructs the compiler that callers should pass in the argument on the stack, but the function should then copy it to a register? Can you cite a reference? (I admit in advance I can't cite a reference for my assertion that it asks to pass the argument in a register. And we all know the register keyword is more or less an unfunny joke to the compiler anyway.) -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue18090 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue18090] dict_contains first argument declared register, and shouldn't be
New submission from Larry Hastings: I'm monkeying around with CPython trunk, and just noticed the following declaration in Objects/dictobject.c: static PyObject * dict_contains(register PyDictObject *mp, PyObject *key) Although dict_contains is a static method, it's cast to PyCFunction and stored in the methoddef array for the dict class. Therefore it must be callable when cast to a PyCFunction--indeed, that's the only way it is ever called. Although the register keyword is at best a vague hope, surely it'd be bad news if our wish was granted? The first argument to the PyCFunction typedef is *not* declared register. So if the caller pushed the first argument on the stack, and dict_contains went looking for its first argument in a register... kablooey. Surely we must remove the register keyword to this function, and similarly clean up all other functions ever cast to PyCFunction or PyCFunctionWithKeywords. The register keyword isn't just a euphemism for I want this code to go faster -ly yours, -- components: Interpreter Core messages: 190263 nosy: larry priority: low severity: normal stage: needs patch status: open title: dict_contains first argument declared register, and shouldn't be type: behavior versions: Python 3.4 ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue18090 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
