pack_float, pack_double, save_float: All the routines for creating
IEEE-format packed representations of floats and doubles simply ignored
that rounding can (in rare cases) propagate out of a long string of
1 bits. At worst, the end-off carry can (by mistake) interfere with
the exponent value, and then unpacking yields a result wrong by a factor
of 2. In less severe cases, it can end up losing more low-order bits
than intended, or fail to catch overflow *caused* by rounding.
(Most of) SF patch 601369 (Christos Georgiou): obmalloc,structmodule:
64bit, big endian (issue 2 only).
This adds a bunch of memcpy calls via a temporary variable to avoid
alignment errors. That's needed for some platforms.
The ob_sval member of a string object isn't necessarily aligned to better
than a native long, so the new "q" and "Q" struct codes can't get away w/
casting tricks on platforms where LONG_LONG requires stricter-than-long
alignment. After I thought of a few elaborate workarounds, Guido bashed
me over the head with the obvious memcpy approach, herewith implemented.
This completes the q/Q project.
longobject.c _PyLong_AsByteArray: The original code had a gross bug:
the most-significant Python digit doesn't necessarily have SHIFT
significant bits, and you really need to count how many copies of the sign
bit it has else spurious overflow errors result.
test_struct.py: This now does exhaustive std q/Q testing at, and on both
sides of, all relevant power-of-2 boundaries, both positive and negative.
NEWS: Added brief dict news while I was at it.
native mode, and only when config #defines HAVE_LONG_LONG. Standard mode
will eventually treat them as 8-byte ints across all platforms, but that
likely requires a new set of routines in longobject.c first (while
sizeof(long) >= 4 is guaranteed by C, there's nothing in C we can rely
on x-platform to hold 8 bytes of int, so we'll have to roll our own;
I'm thinking of a simple pair of conversion functions, Python long
to/from sized vector of unsigned bytes; that may be useful for GMP
conversions too; std q/Q would call them with size fixed at 8).
test_struct.py: In addition to adding some native-mode 'q' and 'Q' tests,
got rid of unused code, and repaired a non-portable assumption about
native sizeof(short) (it isn't 2 on some Cray boxes).
libstruct.tex: In addition to adding a bit of 'q'/'Q' docs (more needed
later), removed an erroneous footnote about 'I' behavior.
where sizeof(long)==8. This *was* broken on boxes where signed right
shifts didn't sign-extend, but not elsewhere. Unfortunately, apart
from the Cray T3E I don't know of such a box, and Guido has so far
refused to buy me any Cray machines for home Python testing <wink>.
More immediately interesting would be if someone could please test
this on *any* sizeof(long)==8 box, to make sure I didn't break it.
Add definitions of INT_MAX and LONG_MAX to pyport.h.
Remove includes of limits.h and conditional definitions of INT_MAX
and LONG_MAX elsewhere.
This closes SourceForge patch #101659 and bug #115323.
and a couple of functions that were missed in the previous batches. Not
terribly tested, but very carefully scrutinized, three times.
All these were found by the little findkrc.py that I posted to python-dev,
which means there might be more lurking. Cases such as this:
long
func(a, b)
long a;
long b; /* flagword */
{
and other cases where the last ; in the argument list isn't followed by a
newline and an opening curly bracket. Regexps to catch all are welcome, of
course ;)
