Error detecting attributes (g++-3.3)

[Andy Dougherty <doughera@…>]

I'm forwarding this to Trac so it doesn't get lost.  The original problem 
manifested itself on the openbsd smoker in the gcc compile farm, but is 
likely more general than that.

-- 
    Andy Dougherty		doughera@lafayette.edu

---------- Forwarded message ----------
Date: Mon, 25 Jul 2011 19:53:31 -0400 (EDT)
From: Andy Dougherty <doughera@lafayette.edu>
To: Jonathan "Duke" Leto <jonathan@leto.net>
Cc: parrot-dev <parrot-dev@lists.parrot.org>
Subject: Re: compile error on openbsd with g++

On Sat, 23 Jul 2011, Andy Dougherty wrote:

> On Fri, 22 Jul 2011, Jonathan "Duke" Leto wrote:
> 
> > gcc (GCC) 3.3.5 (propolice)

> > On Fri, Jul 22, 2011 at 10:49 AM, Jonathan "Duke" Leto
> > <jonathan@leto.net> wrote:
> > > Howdy,
> > >
> > > Just got the openbsd smoker in the farm working again, and it hit a
> > > compile error:
> > >
> > > https://gist.github.com/1099956
> 
> Without seeing both the output of Configure.pl --verbose and the 
> preprocessed output of src/string/api.c, it's hard to be sure, but this 
> looks like the sort of thing you get when parrot's detection of attributes 
> is wrong.
> 
> In particular, the gcc-3.3/HASATTRIBUTE_UNUSED combination is tricky:  It 
> works in gcc-3.3, but fails in g++-3.3.

I haven't tested this at all, but I suspect that the issue is that the 
Configure.pl probe doesn't use the attribute in the same way as parrot 
does.  (The inline probe has the same problem.  See TT #1943).

It's likely that a rather trivial patch like the one below will fix this 
immediate problem, but since my last 2 attempts to do something useful for 
attribute detection were rejected, I'm unwilling to work any harder at it.

diff --git a/config/auto/attributes/test_c.in b/config/auto/attributes/test_c.in
index eb5262c..896da8b 100644
--- a/config/auto/attributes/test_c.in
+++ b/config/auto/attributes/test_c.in
@@ -42,7 +42,7 @@ coldfunc(int x);
 
 
 static int
-useless(void) { int x __attribute__unused__; return 0; }
+useless(int x __attribute__unused__) { int y __attribute__unused__; return 0; }
 
 
 /* as long as the file compiles, everything is okay */



-- 
    Andy Dougherty		doughera@lafayette.edu

[doughera@…]

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[jkeenan]

I have converted Andy Dougherty's patch to an attachment. I tried it out on both Linux/i386 and Darwin/PPC with no harm; all tests PASS. However, in both cases I was using gcc or g++ 4+. So, it still needs to be tested for the case for which it was designed.

kid51