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Date:   Thu, 23 Apr 2020 18:16:56 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     Alexandre Chartre <alexandre.chartre@oracle.com>
Cc:     jpoimboe@redhat.com, linux-kernel@vger.kernel.org,
        jthierry@redhat.com, tglx@linutronix.de, x86@kernel.org,
        mbenes@suse.cz
Subject: Re: [PATCH 3/8] objtool: Rework allocating stack_ops on decode
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On Thu, Apr 23, 2020 at 05:40:38PM +0200, Alexandre Chartre wrote:
> 
> On 4/23/20 2:47 PM, Peter Zijlstra wrote:
> > Wrap each stack_op in a macro that allocates and adds it to the list.
> > This simplifies trying to figure out what to do with the pre-allocated
> > stack_op at the end.
> > 
> > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> > ---
> >   tools/objtool/arch/x86/decode.c |  257 +++++++++++++++++++++++-----------------
> >   1 file changed, 153 insertions(+), 104 deletions(-)
> > 
> > --- a/tools/objtool/arch/x86/decode.c
> > +++ b/tools/objtool/arch/x86/decode.c
> > @@ -77,6 +77,17 @@ unsigned long arch_jump_destination(stru
> >   	return insn->offset + insn->len + insn->immediate;
> >   }
> > +#define PUSH_OP(op) \
> > +({ \
> > +	list_add_tail(&op->list, ops_list); \
> > +	NULL; \
> > +})
> > +
> > +#define ADD_OP(op) \
> > +	if (!(op = calloc(1, sizeof(*op)))) \
> > +		return -1; \
> > +	else for (; op; op = PUSH_OP(op))
> > +
> 
> I would better have a function to alloc+add op instead of weird macros,
> for example:

I know it'll not make you feel (much) better, but we can write it
shorter:

+#define ADD_OP(op) \
+       if (!(op = calloc(1, sizeof(*op)))) \
+               return -1; \
+       else for (list_add_tail(&op->list, ops_list); op; op = NULL)

Also, the kernel is full of funny macros like this ;-)