Re: Comments on pmake diffs for building on Linux

On Tue, 4 Mar 2008, M. Warner Losh wrote:

> : In most ports of FreeBSD parts to Linux that I've seen, the preferred solution
> : has to been to bring the entire FreeBSD queue.h with you rather than relying
> : on the native Linux queue.h.  This is what we do for OpenBSM, for example;
> : this also helps out when you get to Mac OS X, Solaris, etc, where all the
> : queue.h's continue to vary in subtle ways.  This depends a fair amount on a
> : lack of header pollution in the OS's own include files, of course...
>
> I was rather hoping for something that could be used without any of that 
> nonsense...

Sadly, nonsense seems to be the name of the game in software portability. 
Here's the broken autoconf garbage I use to pick out adequate queue.h's from 
inadequate ones:

# sys/queue.h exists on most systems, but its capabilities vary a great deal.
# test for LIST_FIRST and TAILQ_FOREACH_SAFE, which appears to not exist in
# all of them, and are necessary for OpenBSM.
AC_TRY_LINK([
         #include <sys/queue.h>
], [

         #ifndef LIST_FIRST
         #error LIST_FIRST missing
         #endif
         #ifndef TAILQ_FOREACH_SAFE
         #error TAILQ_FOREACH_SAFE
         #endif
], [
AC_DEFINE(HAVE_FULL_QUEUE_H,, Define if queue.h includes LIST_FIRST)
])

Note that there are at least a couple of mostly stylistic bugs there (could 
use compile rather than link, definition description is poor, errors are 
inconsistent). :-)  I found that on both Linux and Mac OS X, the queue.h's 
didn't have everything I wanted.

Robert N M Watson
Computer Laboratory
University of Cambridge
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