Comments on pmake diffs for building on Linux

[M. Warner Losh]

In message: <20080304154542.GC61036 at kobe.laptop>
            Giorgos Keramidas <keramida at ceid.upatras.gr> writes:
: On 2008-03-04 15:38, Robert Watson <rwatson at freebsd.org> wrote:
: > 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.
: 
: Nice!  Thank you Robert.  Can I copy parts of this and add them to the
: autoconf glue I'm adding now?
: 
: To test just cpp(1) stuff, autoconf supports AC_PREPROC_IFELSE() too,
: which I used when I tried writing a check for __FBSDID():
: 
:   AC_PREPROC_IFELSE(
:     [AC_LANG_PROGRAM([[#include <sys/cdefs.h>
:   #ifndef __FBSDID
:   #error No __FBSDID definition.
:   #endif]])],
:     [AC_DEFINE([HAVE_FBSDID_MACRO], [1],
:        [Define to 1 if you have the __FBSDID macro.])])
: 
: I can probably improve a bit the queue.h check using what you wrote
: above and AC_PREPROC_IFELSE().

The alternative to uglifying the make sources with #ifdefs would be to
just always use the compat includes when building...  No autoconf
needed, and minimal changes to the base make, if any.

Warner