Re: [Chromium-dev] "special" functions

[Robert E. <pa...@tu...>]

> throughout the code I'm finding files with the name "*_special" that  
> list some subset of the OpenGL API. I'm having a hard time deciphering  
> for each of these files what criteria causes a function to end up  
> here. They are obviously manually constructed.

The "*_special" files are typically used with Python code generation scripts, 
and indicate a function that for some reason or another cannot be handled with 
automatically generated code, and instead must be handled with "special" code.

Sometimes this is because the code generation script isn't complete (and 
complex) enough to handle all possible generic function specifications (from 
APIspec.txt); sometimes it doesn't make sense to spend hours carefully crafting 
the code generator to handle just a few unusual cases that you could otherwise 
code in a few minutes.

Sometimes it's because APIspec.txt doesn't include just the right classification 
code for a group of functions that could be used to automatically generate code 
for them; the only alternative to defining a new classification and going 
through every function in APIspec.txt to figure out which functions need the 
classification (a very pervasive action) is to create a "*_special" file.

Sometimes it's because the whole point of a generated SPU is to provide special 
implementations of just certain functions, while providing common handling for 
all others (e.g. the "expando" SPU).

Sometimes it's because some functions or classes of functions really need 
special handling that can't be automated for a given use.

In general, unfortunately, you have to have a pretty intimate understanding of 
what sort of code generation is going on and why in order to figure out what 
belongs in a "*_special" file.  That's hard enough if you're modifying an SPU, 
but quite a bit more difficult if you're adding functions to APIspec.txt.

As a first pass, I'd recommend the same thing Brian did: find functions that 
behave like the new functions do, and make their entries in APIspec.txt and 
"*/*_special" files similar.  As you test, you'll inevitably find places that 
you missed or incorrect categorizations; fix the ones that you find, and the 
next guy will fix the ones that he finds, etc...

Bob Ellison
Tungsten Graphics, Inc.