mirrors/cpython
1
0
Fork 0
mirror of https://github.com/python/cpython.git synced 2025-08-04 00:48:58 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions 8

Fix the internals of our hash functions to used unsigned values during hash

Browse source 
computation as the overflow behavior of signed integers is undefined.

NOTE: This change is smaller compared to 3.2 as much of this cleanup had
already been done.  I added the comment that my change in 3.2 added so that the
code would match up.  Otherwise this just adds or synchronizes appropriate UL
designations on some constants to be pedantic.

In practice we require compiling everything with -fwrapv which forces overflow
to be defined as twos compliment but this keeps the code cleaner for checkers
or in the case where someone has compiled it without -fwrapv or their
compiler's equivalent.  We could work to get rid of the -fwrapv requirement
in 3.4 but that requires more planning.

Found by Clang trunk's Undefined Behavior Sanitizer (UBSan).

Cleanup only - no functionality or hash values change.
This commit is contained in:
Gregory P. Smith 2012-12-10 19:51:29 -08:00
commit 27dc02e8c5
4 changed files with 12 additions and 12 deletions
Download patch file Download diff file Expand all files Collapse all files

2
Include/pyport.h
View file

@ -145,7 +145,7 @@ Used in: PY_LONG_LONG
#endif
/* Prime multiplier used in string and various other hashes. */
#define _PyHASH_MULTIPLIER 1000003 /* 0xf4243 */
#define _PyHASH_MULTIPLIER 1000003UL /* 0xf4243 */
/* Parameters used for the numeric hash implementation. See notes for
_Py_HashDouble in Objects/object.c. Numeric hashes are based on