[XviD-devel] ia64-Patch

[Christoph Lampert]

On Sat, 25 Jan 2003, Stephan Krause wrote:

> Hi,
> 
> after a longer time i checked the code for ia64 compatibility, and it did 
> segfault in mbcoding. Reason was a uint32 which became -1. On 32bit-Platforms 
> this is not a Problem, but on ia64 this isn't a really good idea. Using ptr_t 
> instead of uint32 does help (on x86, ptr_t is just the same as uint32_t)

Yes, we should really take more care about correct types, in particular
with "64bit for everybody" around the corner: 

My suggestion: 

* Use "natural" types where possible. Use "int" instead of int32_t, etc.,
  unless the size matters (which it almost never does). The _size_ of
  structures doesn't have to be the same on every plattform... 

* Of course, things like "uint8_t" for 8bit images and "int16_t" for
  DCT data must be the same, but e.g. length of MV entries doesn't have 
  to. I doubt that XVID will ever run successfully on a machine with 
  16bit integers, so range should always be sufficient... 

* Use  unsigned int  for loop counters (I read somewhere that it's
  faster), unless they become negative, of course.

* When in doubt, use signed types (in particular SAD-values, MVs)

* For status values, used signed types (speed doesn't matter there, and 
  often negative values are useful to indicate errors. 

* Use _signed_ for stride values, they are a "relative" value and might
  become negative.

* For hacks which use bit-patterns etc. to speed up calculation, use 
  "sizeof()", or define plattform dependent macros in portab.h 

Better ideas?

gruel