[Python-Dev] Py_DECREF causes spurious gcc warning
tim.one at comcast.net
Sat Dec 20 14:35:34 EST 2003
>>> It does, however, lead to a different problem:
>>> if (condition)
>>> Py_DECREF (foo);
>>> else // oops, syntax error here
[Martin v. Löwis]
>> How so? This expands to
>> else action2;
> No, it expands to
> if(cond2) action1;
> else action2;;
> -- note the extra semicolon, which provokes a syntax error.
Zack, which version of Python are you using? The current definition of
Py_DECREF doesn't end with a semicolon:
#define Py_DECREF(op) \
if (_Py_DEC_REFTOTAL _Py_REF_DEBUG_COMMA \
--(op)->ob_refcnt != 0) \
The expansion of _Py_CHECK_REFCNT(op) always ends with a semicolon (and may
be nothing but a semicolon, depending on build type), but that's internal to
the stuff Py_DECREF generates, and the leading underscore in
_Py_CHECK_REFCNT's name makes it off-limits (by convention) for direct use
by user-written code (_Py_CHECK_REFCNT is internal to Python's
implementation, and Python internals guarantee to use it correctly).
The expansion of Py_DECREF's else branch never ends with a semicolon, and
Martin's explanation is correct.
Same deal with Py_INCREF, Py_XINCREF, and Py_XDECREF.
As a pragmatic matter, it's very unusual to need to do
The functionality is common enough when "whatever" is "op != NULL", but
accomplishing "decref if not NULL" is Py_XDECREF's purpose -- there's no
need to code your own if-block in that case, and it's bad style (because
non-idiomatic) to do so.
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