[ python-Bugs-994255 ] Py_RETURN_NONE causes too much warnings

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Bugs item #994255, was opened at 2004-07-20 00:36
Message generated for change (Comment added) made by thiagocorrea
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Category: Python Interpreter Core
Group: Python 2.4
Status: Open
Resolution: None
Priority: 5
Submitted By: Correa (thiagocorrea)
Assigned to: Nobody/Anonymous (nobody)
Summary: Py_RETURN_NONE causes too much warnings

Initial Comment:
It will make the compiler complain on each instance
about the conditional being constant ( while (0) )

why not use something like this instead?

The compiler will be able to optimize out the function
call.

#if !defined(Py_RETURN_NONE) // New in Python 2.4
inline PyObject* doPy_RETURN_NONE()
{	Py_INCREF(Py_None); return Py_None; }
#define Py_RETURN_NONE return doPy_RETURN_NONE()
#endif

#if !defined(Py_RETURN_TRUE) // New in Python 2.4
inline PyObject* doPy_RETURN_TRUE()
{Py_INCREF(Py_True); return Py_True;}
#	define Py_RETURN_TRUE return doPy_RETURN_TRUE()
#endif

#if !defined(Py_RETURN_FALSE) // New in Python 2.4
inline PyObject* doPy_RETURN_FALSE()
{Py_INCREF(Py_False); return Py_False;}
#define Py_RETURN_FALSE return doPy_RETURN_FALSE()
#endif


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>Comment By: Correa (thiagocorrea)
Date: 2004-07-20 23:26

Message:
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I'm not building Python.
I use python embedded on my project ( sf.net/projects/wpdev
) for scripting.

I often build using Level 4 warning (/W4) setting, usefull
for finding bugs. Also, it's built using C++ compiler not C.

Well, I don't know much about C standards but I do know a
lot about C++, and for C++ inline is just a hint to the
compiler, it might very well completely ignore it or ( it
usually does ) inline functions that were not marked as
"inline". If that's the problem, then drop the "inline"...
or have a macro to detect that inline is supported by the
compiler.
#ifdef __cplusplus
#define INLINE inline
#else
#define INLINE
#endif

Other checks could be added as well to enable it on C99
compliant compilers.
The point here is that the compiler is right complainning
about the constant conditional there.
I know that a simple {} block doesn't work well, but a
function call will, and the call itself will also be
optimized out by the compiler.

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Comment By: Tim Peters (tim_one)
Date: 2004-07-20 22:26

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"do {...} while(0)" is the standard C idiom for writing a multi-
statement macro; the reason "{...}" doesn't work is 
explained, e.g., here:

http://www.eskimo.com/~scs/C-faq/q10.4.html

thiagocorrea, we need more words from you.  Python is built 
every day using MSVC 6.0, and Visual Studio 7.1, with no 
warnings of any kind.  Indeed, "no warnings under MSVC" is a 
groundrule for the Python project.  Exactly how do you 
compile it?  Do you use the Visual Studio project files in the 
PCBuild subdirectory?

Brett is correct that we cannot use "inline" either.

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Comment By: Brett Cannon (bcannon)
Date: 2004-07-20 21:40

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You can't use inline; that is not supported in C89 but only C99 which we 
do not support.

As for why we can't just make the macro ``{Py_INCREF(Py_None); 
return Py_None;}``, I don't know.  K&R seems to suggest that the syntax 
is at least legal.

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Comment By: Correa (thiagocorrea)
Date: 2004-07-20 12:27

Message:
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Visual C++ 7.0, Win32



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Comment By: Raymond Hettinger (rhettinger)
Date: 2004-07-20 08:27

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Which compiler and operating system are you using?

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