On Thu, Oct 1, 2015 at 10:35 AM, Yaakov Selkowitz <yselkow...@cygwin.com> wrote: > > Confirmed. Often 64-bit-only issues come down to one or more of the > following: > > * implicit function declarations. Per the C standard, argument types > are assumed to match whatever is given (which may be wrong if e.g. 0 is > used instead of 0L or (PointerType)0 or NULL etc.) and the return type > is assumed to be int (which will truncate the actual return value when > it is actually a long/pointer). > > * vararg types. Because these types aren't declared, the compiler can't > automatically cast values to the correct type, so literal values and > symbolic constants must be explicitly cast if they are not meant to be > an int and are not obviously a long/pointer. >
Good list. I would also add attempting to store pointer differences in an "int" instead of ptrdiff_t and the issue you can see from https://en.wikipedia.org/wiki/64-bit_computing#64-bit_data_models, which is that the integer types other than long long on 64-bit Windows are 32-bits while on 64-bit Linux 'long' and 'long long' are both 64-bit. This issue means that 'long' is a good-enough hack for ptrdiff_t on 64-bit Linux but not 64-bit Windows. Does Cygwin differ from Windows itself on this issue? Most 32-bit-designed code is probably more sensitive to the pointer-difference aspect of this. -- Problem reports: http://cygwin.com/problems.html FAQ: http://cygwin.com/faq/ Documentation: http://cygwin.com/docs.html Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple
