Is isysroot useful for non-universal?

[Ryan Schmidt]

On Mar 21, 2009, at 21:34, Marcus Calhoun-Lopez wrote:

> It is mentioned in http://trac.macports.org/ticket/17356#comment:6
> that universal builds do not suffer from bad .la files because of - 
> isysroot.

That ticket specifically talks about bad .la files installed by some  
Apple software, relating to X11. We should not need workarounds in  
MacPorts for these bad files. Apple should distribute software  
updates to fix the bad files they installed. Further, this specific  
problem is no longer observed for the majority of users who will  
presumably not have selected the +system_x11 variant.


> Perhaps -isysroot could be used to solve other problems as well.

What kinds of problems? Do you mean those kinds of problems that  
arise from the user installing things in /usr/local and MacPorts- 
installed software inadvertently linking with it?

> If I understand the behavior, any compiler call with
> -isysroot would not see /usr/local/include.

 From where do you get that understanding? Is this from the fact that  
there is no /Developer/SDKs/*/usr/local/include? Any documentation  
you have on -isysroot would be helpful; I know nothing about it other  
than the way in which Apple says to use it for building a universal  
binary.

> It also does not see any changes the user might have made.

What kinds of changes are you talking about? Do you mean rogue  
software installed by the user in system prefixes like / and /usr? I  
suppose this would help MacPorts avoid linking with additional  
software the user has installed there. I don't see it helping if the  
user has replaced existing software.

> -Wl,-syslibroot,${SDK} might be used in a similar manner
> (for user changes anyway).
> It would still see /use/local/lib since
> /Developer/SDKs/*/usr/local/lib exists and is a link to /usr/local/ 
> lib.

I see.

> One big downside is that the Apple developer pages say that
> support of isysroot "is likely to change in the future. "
>
> Even still, might isysroot and syslibroot be used to cut down on  
> bug reports?