Re: [Cocci] Using a macro for variable attributes

[Paul Chaignon <paul@cilium.io>]

Thanks for the quick answer!

On Tue, Apr 28, 2020 at 07:44:15PM +0200, Julia Lawall wrote:
> 
> 
> On Tue, 28 Apr 2020, Paul Chaignon wrote:
> 
> > Hi all,
> >
> > I am working on a small semantic patch to annotate specific variables in
> > our codebase with __attribute__((aligned(8))). The following program works
> > fine.
> >
> >   @r@
> >   expression e1, e2;
> >   identifier x;
> >   @@
> >   (
> >     struct \(icmphdr\|icmp6hdr\) x
> >   + __attribute__((aligned(8)))
> >     ;
> >   |
> >     struct \(icmphdr\|icmp6hdr\) x
> >   + __attribute__((aligned(8)))
> >     = ...;
> >   )
> >     ... when exists
> >     ctx_load_bytes(e1, e2, &x, ...)
> >
> > However, when I replace __attribute__((aligned(8))) with our internal
> > macro __align_stack_8, it fails with the following error:
> >
> >   plus: parse error:
> >     File "/home/paul/cilium/contrib/coccinelle/aligned.cocci", line 7, column 2, charpos = 77
> >     around = '__align_stack_8',
> >     whole content = + __align_stack_8
> >
> > I've tried adding '#define __align_stack_8' in a file passed with
> > --macro-file, without success. Is this a known limitation for macros or
> > am I missing something?
> 
> Try adding the "metavariable" declaration:
> 
> attribute name __align_stack_8;

Awesome, that worked. And I think I understand: undeclared identifiers are by
default considered symbols, leading to the parse error.

Unfortunately, my semantic patch now leads to the following changes:

  -	struct icmphdr icmphdr __align_stack_8;
  +	struct icmphdr icmphdr __align_stack_8 __align_stack_8;

I would normally add a first case to my conjunction to match on
already-present attributes, but Coccinelle can't match on attributes yet.
Any workaround?

Paul
_______________________________________________
Cocci mailing list
Cocci@systeme.lip6.fr
https://systeme.lip6.fr/mailman/listinfo/cocci