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Re: SvUPGRADE and void
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From:
Dave Mitchell
Date:
December 14, 2012 17:49
Subject:
Re: SvUPGRADE and void
Message ID:
20121214174859.GK1842@iabyn.com
On Fri, Dec 14, 2012 at 03:22:15PM +0000, Dave Mitchell wrote:
> On Fri, Dec 14, 2012 at 01:22:42PM +0000, Nicholas Clark wrote:
> > On Thu, Dec 13, 2012 at 01:14:28PM +0000, Dave Mitchell wrote:
> >
> > > The first is to stick a (void) in front of every bare SvUPGRADE() in the
> > > the perl distribution (including dist/ and, via rt.cpan.org, cpan/).
> > > This seems like quite a bit of effort and is a retrograde step.
> >
> > And, arguably, on every distribution on CPAN that also generates a warning?
> >
> > > The second is to bite the bullet and change SvUPGRADE from an expression
> > > into a statement; i.e.
> > >
> > > #define SvUPGRADE(sv, mt) (SvTYPE(sv) >= (mt) || (sv_upgrade(sv, mt), 1))
> > >
> > > becomes
> > >
> > > #define SvUPGRADE(sv, mt) if (sv->type >= (mt)) { sv_upgrade(sv, mt); }
> > >
> > > A search for 'if.*SvUPGRADE' on grep.cpan.me indicates that about 15
> > > distributions would fail to compile and need fixing.
> > >
> > > I'm open to other suggestions.
> >
> > I think we should bit the bullet and go for it. For anything that needs
> > changing, it's a build-time error from the C compiler? (with an easy fix)
> > That's not going to break anything in production.*
>
> Ok, I've bitten the bullet.
... and broken g++.
Can anyone suggest a definition for SvUPGRADE that works for both of the
forms
SvUPGRADE(...);
(void)SvUPGRADE(...);
on gcc, clang and g++, and doesn't generate warnings?
My new incarnation,
#define SvUPGRADE(sv, mt) \
STMT_START { if (SvTYPE(sv) < (mt)) sv_upgrade(sv, mt); } STMT_END
which expands this this line in regcomp.c:
(void)SvUPGRADE(sv_dat,SVt_PVNV);
into:
(void)do { if (((svtype)((sv_dat)->sv_flags & 0xff)) < (SVt_PVNV)) Perl_sv_upgrade(my_perl, sv_dat,SVt_PVNV); } while (0);
gives this error under g++:
regcomp.c:8653:35: error: expected primary-expression before ‘do’
regcomp.c:8653:35: error: expected ‘;’ before ‘do’
while the old version:
#define SvUPGRADE(sv, mt) (SvTYPE(sv) >= (mt) || (sv_upgrade(sv, mt), 1))
gave warnings under clang for this form:
SvUPGRADE(...);
--
Diplomacy is telling someone to go to hell in such a way that they'll
look forward to the trip
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