Previously when combining multiple classic indices into a single classic
index, the contents of source indices are read in as char. During the
interleaving process, depending on the current position of the destination
index, both left and right shifts on the next char could be performed.
However, there are a few undefined behaviours that could affect the results
depending on the platform:
The signedness of a char is an undefined behaviour. Hence when
bit shifting, the usual arithmetic conversion performed on the char is
undefined. The char could be promoted to either signed int or unsigned
int.
If the char is treated as signed int, the bit shifting (both left and
right) is also undefined in pre-c++20 standards. The behaviour is platform
dependent.
This change fixes the issue by declare the contents read from source
indices as unsigned char.
…ndices
Previously when combining multiple classic indices into a single classic index, the contents of source indices are read in as
char. During the interleaving process, depending on the current position of the destination index, both left and right shifts on the next char could be performed.However, there are a few undefined behaviours that could affect the results depending on the platform:
charis an undefined behaviour. Hence when bit shifting, the usual arithmetic conversion performed on the char is undefined. The char could be promoted to either signed int or unsigned int.This change fixes the issue by declare the contents read from source indices as
unsigned char.