[Python-Dev] Proper usage of size_t (original) (raw)

Tim Peters tim.one at comcast.net
Thu Sep 4 22:37:17 EDT 2003

[Martin von Loewis]

On Win64, the Windows SDK compiler gives tons of warnings that type conversions may involve truncation. For example, in 2.3 stringobject.c, a subset of the warnings is

..\Objects\stringobject.c(285) : warning C4267: '=' : conversion from 'sizet' to 'int', possible loss of data ..\Objects\stringobject.c(316) : warning C4244: 'function' : _conversion from 'int64' to 'int', possible loss of data ..\Objects\stringobject.c(554) : warning C4244: 'function' : _conversion from 'int64' to 'int', possible loss of data ..\Objects\stringobject.c(812) : warning C4267: 'function' : conversion from 'sizet' to 'int', possible loss of data ..\Objects\stringobject.c(2154) : warning C4244: 'function' : _conversion from 'int64' to 'int', possible loss of data ..\Objects\stringobject.c(3410) : warning C4267: 'return' : conversion from 'sizet' to 'int', possible loss of data ..\Objects\stringobject.c(3618) : warning C4267: 'return' : conversion from 'sizet' to 'int', possible loss of data ..\Objects\stringobject.c(3737) : warning C4244: '=' : conversion _from 'int64' to 'int', possible loss of data ..\Objects\stringobject.c(4072) : warning C4244: '=' : conversion _from 'int64' to 'int', possible loss of data ..\Objects\stringobject.c(4076) : warning C4244: '=' : conversion _from 'int64' to 'int', possible loss of data These warnings occur for stuff like i = strlen(p); where i is of type int, but strlen returns sizet, and that might exceed what int can store. Likewise, in PyStringResize(&string, s - PyStringASSTRING(string)); the pointer difference is of type sizet, but PyStringResize expects int. I'd be willing to go through and replace "int" by "sizet" whereever I find it appropriate, for Python 2.4.

I've done that often in the past, but piecemeal. Note that another raft of changes usually follows from this: it's not only the size of the integral type that may change, but regardless of platform it's also a change from a signed type to an unsigned type. That often triggers a new round of warnings (e.g., MSVC6 warns when mixing signed and unsigned in comparisons).

I would keep the current object layout for the moment, but change function signatures, which would cause ABI breakage on platforms where sizeof(sizet)!=sizeof(int).

What do you think?

It's overdue -- go for it! +1.

More information about the Python-Dev mailing list