[Bf-committers] note to developers about 32 vs 64 bit long datatypes

Lukas Tönne lukas.toenne at googlemail.com
Wed Oct 26 11:33:16 CEST 2011

I recently came across a similar issue when working on random number
generation for particles. I copied part of the code in
BLI_rand.h/rand.c, which uses the common linear congruential generator
[1]. In order to create random numbers over the full 32-bit integer
range, the internal state variable must be a 64-bit integer, and to
ensure this the code uses different typedefs depending on OS:

#if defined(WIN32) && !defined(FREE_WINDOWS)
typedef unsigned __int64	r_uint64;
typedef unsigned long long	r_uint64;

I don't know if this code even takes Win64 into account ... but
according to the standard the awkward "unsigned long long" type should
have *at least* 64 bits.
Imo it would be nice to have a general, reliable, platform-independent
64 bit typedef for this sort of thing.

On Tue, Oct 25, 2011 at 11:42 PM, pete larabell <xgl.asyliax at gmail.com> wrote:
> Hey all, was debugging a new node im making and some discussion on IRC
> lead me to find this:
> http://en.cppreference.com/w/cpp/language/types
> Note that unsigned long, and long are truly DIFFERENT sizes on Win64
> vs Linux64/FreeBSD64/OSX64
> Not sure if anyone else ran into a problem like this, but I thought it
> was worth bringing up to everyone that may be expecting something a
> certain size (for filling out a struct or whatever), it's different
> depending on the platform you compile on.
> Cheers!
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> Bf-committers at blender.org
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