Tim Peters <[EMAIL PROTECTED]> writes:
> marshal shouldn't be representing doubles as decimal strings to begin
> with. All code for (de)serialing C doubles should go thru
> _PyFloat_Pack8() and _PyFloat_Unpack8(). cPickle (proto >= 1) and
> struct (std mode) already do; marshal is the oddball.
>
> But as the docs (floatobject.h) for these say:
>
> ...
> * Bug: What this does is undefined if x is a NaN or infinity.
> * Bug: -0.0 and +0.0 produce the same string.
> */
> PyAPI_FUNC(int) _PyFloat_Pack4(double x, unsigned char *p, int le);
> PyAPI_FUNC(int) _PyFloat_Pack8(double x, unsigned char *p, int le);
> ...
> * Bug: What this does is undefined if the string represents a NaN or
> * infinity.
> */
> PyAPI_FUNC(double) _PyFloat_Unpack4(const unsigned char *p, int le);
> PyAPI_FUNC(double) _PyFloat_Unpack8(const unsigned char *p, int le);
OTOH, the implementation has this comment:
/*----------------------------------------------------------------------------
* _PyFloat_{Pack,Unpack}{4,8}. See floatobject.h.
*
* TODO: On platforms that use the standard IEEE-754 single and double
* formats natively, these routines could simply copy the bytes.
*/
Doing that would fix these problems, surely?[1]
The question, of course, is how to tell. I suppose one could jsut do
it unconditionally and wait for one of the three remaining VAX
users[2] to compile Python 2.5 and then notice.
More conservatively, one could just do this on Windows, linux/most
architectures and Mac OS X.
Cheers,
mwh
[1] I'm slighyly worried about oddball systems that do insane things
with the FPU by default -- but don't think the mooted change would
make things any worse.
[2] Exaggeration, I realize -- but how many non 754 systems are out
there? How many will see Python 2.5?
--
If you give someone Fortran, he has Fortran.
If you give someone Lisp, he has any language he pleases.
-- Guy L. Steele Jr, quoted by David Rush in comp.lang.scheme.scsh
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