[M3devel] "target specific pragmas"?

[Tony Hosking]

So, here's the thing about pragmas.  According to the language  
definition, they can be ignored and the program should still "mean"  
the same thing.  Preprocessing definitely does not fit that model.

On Feb 11, 2008, at 8:21 PM, Jay wrote:

> So I have NOT thought this through.
>
> I wonder if "preprocessing" dependent only on "target" is a good idea.
>
> Something like either the ability to prefix pragmas with a target,  
> or an "iftarget" and "ifnottarget" pragma.
>
> Something like so:
>
> <* IF_TARGET NT386 *>
> <* END_IF_TARGET*>
>
>
> <* IF_TARGET NT386 *>
> <* END_IF_TARGET*>
> It's a small can of worms.
> Where can they be placed? Only at "global" scope? (ie: toplevel in  
> an interface/module).
>
> What about IF_OSTYPE?
> What about expressions?
> IF_TARGET NT386 OR NTAMD64
>
> IF_TARGET STARTS(NT)
>
> etc.
>
> I don't really have enough interest here to work through this, just  
> sending out the bait...
>
> Obviously this was triggered by my happening into the odbc  
> directory and bringing up ignoring WINAPI on non-NT386 or prefixing  
> calling conventions with a target.
>
> This reminds me of an important point here however -- nobody else  
> is going to make the mistake of ever having multiple calling  
> conventions. Therefore the generality of prefixing WINAPI with  
> NT386: is useless.
> Unless Mac68K support is added.
>
> And here is some rationale even. The PC and Mac evolved from  
> "small" systems, where assembly programming was common, more people  
> knew more lower level details and playing games with calling  
> conventions was something anyone could do. Most other current  
> systems are rooted in C programming. Working in C, calling  
> conventions are generally in a hidden layer below what anyone  
> thinks about. Therefore, the smaller number of capable people  
> working at that level have the good sense to only have one calling  
> convention. No more systems will evolve from "small", at least not  
> without having observed this history. Therefore, there will no  
> longer be multiple calling conventions.
>
> That is my theory at least.
>
> Oh, Windows does also have __thiscall and __clrcall. __thiscall is  
> only x86