From: Zefram <A.Main@dcs.warwick.ac.uk>
To: schaefer@nbn.com
Cc: A.Main@dcs.warwick.ac.uk, hzoli@cs.elte.hu, zsh-workers@math.gatech.edu
Subject: Re: Sick macros (was: Action, not words (Re: bug (?) in 3.0-pre1))
Date: Tue, 2 Jul 1996 19:24:26 +0100 (BST) [thread overview]
Message-ID: <18722.199607021824@stone.dcs.warwick.ac.uk> (raw)
In-Reply-To: <960702105235.ZM4305@candle.brasslantern.com> from "Bart Schaefer" at Jul 2, 96 10:52:32 am
>And then I'd write:
>
> HEAPALLOC {
> /* ... stuff ... */
> } LASTALLOC;
>
>That makes the block context obvious. The macros are upper-case because
>I don't like introducing new "keywords".
Yes, I think this is preferable. As we are introducing a new block,
there should be a new indentation level for it, and the braces make it
clearer. And there's a bonus with this syntax:
PERMALLOC
some_function();
LASTALLOC;
is legal, matching other bits of C syntax. I think the size of the
resulting patch should not be a consideration.
>} #define lastalloc_return \
>} if( (nonlocal_useheap ? global_heapalloc() : global_permalloc()) , 0 ) \
>} ; \
>} else \
>} return
>
>Hmm ... I seem to recall that some compilers don't like having void
>expressions (e.g. (?:) where both branches are void functions) used
>anywhere in a comma-expression. In particular, I think AIX either
>rejects this or compiles it wrong. However, I could be confusing that
>with something else ... I know for a fact that AIX could not handle
>an `if (x,y)' construct we used in zmail, forcing us to rewrite it
>as `if (x?0:y)' -- which doesn't work in general, it just happened
>that for us x was always 0 to begin with.
Curious. It's a perfectly legal expression, so any compiler that can't
grok it is broken. However, if a common compiler barfs on that, maybe
we could have global_{heap,perm}alloc() return 0, so the comma operator
is unnecessary and there are no void subexpressions.
>If I'm confused and the comma-expression above turns out to be OK, I'd
>change ALLOC_RESTORE and add LASTALLOC_RETURN:
>
>#define ALLOC_RESTORE \
> ((nonlocal_useheap ? global_heapalloc() : global_permalloc()), 0)
>#define LASTALLOC_RETURN if (ALLOC_RESTORE); else return
Cleaner, I think, to have
#define ALLOC_RESTORE \
( nonlocal_useheap ? global_heapalloc() : global_permalloc() )
#define LASTALLOC_RETURN if(ALLOC_RESTORE, 0) ; else return
but the semantics of these two are identical. ("ALLOC_RESTORE;" is a
legal statement in both cases.)
> if (getmeoutofhere()) {
> ALLOC_RESTORE;
> return(-1);
> }
I'd rather have the convenience of LASTALLOC_RETURN -- at least, if
this is often required.
-zefram
next prev parent reply other threads:[~1996-07-02 18:36 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
1996-06-28 17:12 bug (?) in 3.0-pre1 gene
1996-06-28 17:50 ` Zoltan Hidvegi
1996-06-28 19:04 ` Steven L Baur
1996-06-29 19:13 ` Bart Schaefer
1996-06-30 16:13 ` Zoltan Hidvegi
1996-06-30 19:21 ` Bart Schaefer
1996-06-30 21:50 ` Action, not words (Re: bug (?) in 3.0-pre1) Bart Schaefer
1996-07-02 7:24 ` Sick macros (was: Action, not words (Re: bug (?) in 3.0-pre1)) Zefram
1996-07-02 17:52 ` Bart Schaefer
1996-07-02 18:24 ` Zefram [this message]
1996-07-02 19:19 ` Bart Schaefer
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