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| author | Tim Peters <tim.peters@gmail.com> | 2003-03-20 18:32:13 (GMT) |
|---|---|---|
| committer | Tim Peters <tim.peters@gmail.com> | 2003-03-20 18:32:13 (GMT) |
| commit | d50ade68ec240ea8ea12604809d8c70985263dce (patch) | |
| tree | 7dd938bc5a9dcf40707839e518420804bbb3cd94 /Misc | |
| parent | 62364ffb80a7dab0477fe7dc7aec5478ab6afec2 (diff) | |
| download | cpython-d50ade68ec240ea8ea12604809d8c70985263dce.zip cpython-d50ade68ec240ea8ea12604809d8c70985263dce.tar.gz cpython-d50ade68ec240ea8ea12604809d8c70985263dce.tar.bz2 | |
SF bug 705836: struct.pack of floats in non-native endian order
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.
Bugfix candidate, but I already backported this to 2.2.
In 2.3, this code remains in severe need of refactoring.
Diffstat (limited to 'Misc')
| -rw-r--r-- | Misc/NEWS | 8 |
1 files changed, 8 insertions, 0 deletions
@@ -37,6 +37,14 @@ Core and builtins Extension modules ----------------- +- The platform-independent routines for packing floats in IEEE formats + (struct.pack's <f, >f, <d, and >d codes; pickle and cPickle's protocol 1 + pickling of floats) ignored that rounding can cause a carry to + propagate. The worst consequence was that, in rare cases, <f and >f + could produce strings that, when unpacked again, were a factor of 2 + away from the original float. This has been fixed. See SF bug + #705836. + - New function time.tzset() provides access to the C library tzet() function, if supported. (SF patch #675422.) |