Christian Tismer wrote:
On 7/22/09 4:56 PM, Roumen Petrov wrote:
Martin v. Löwis wrote: [SNIP]
No. tim_one changed it to be long double in r25454 to support some system that Dave Abrahams uses, so it needs to stay that way :-)
However, we can certainly acknowledge that this is a bug in MingW, and special case it. Either introduce a symbolic type gchead_align_t which gets defined to just double on MingW, or put the #ifdef right into the structure.
No this is not GCC bug. GCC support "hardware extended precision" as implement long double and mingw w32api implement long double functions. According to http://msdn.microsoft.com/en-us/library/9cx8xs15.aspx it is MSVC limitation.
It might also be useful to assert that sizeof(gchead_align_t) is 8 or 16, and reject 12 as a value. The point is that we need the maximum alignment, and that certainly shouldn't be 12.
So look like python bug.
The assumption is that the union with long double gives alignment to the largest possible integral type with a power of 2 size, which is then wrong, because of the unexpected size.
As is posted for GCC on linux(32-bit) size of structure is 12 = sizeof(struct in union) = sizeof(pointer)+sizeof(pointer)+sizeof(ssize_t). And sizeof(ssize_t) <= sizeof(long) <= sizeof(pointer) .
What do you propose for doing proper alignment, then?
May be "void* dummy[4]" is better for force alignment ? What about alignment on platforms with pointers > 32 bit ?
I fear this needs to become yet another special case in pyconfig.h
cheers - chris
Regards, Roumen