Re: alloca is bad?

[Michael Meissner <meissner at cygnus dot com>]

On Fri, Nov 10, 2000 at 11:42:48AM -0500, Fernando Nasser wrote:
> Chris Faylor wrote:
> > 
> > On Fri, Nov 10, 2000 at 05:39:29AM -0500, Eli Zaretskii wrote:
> > >> Date: Thu, 9 Nov 2000 21:20:32 -0500
> > >> From: Christopher Faylor <cgf@redhat.com>
> > >>
> > >> I was surprised by this assertion and so I thought I'd ask for a
> > >> consensus here.  Should the use of alloca be deprecated in gdb?
> > >
> > >In my experience, there's nothing wrong with alloca as long as it is
> > >used for allocating small buffers.  The only consideration is that not
> > >every platform supports alloca.
> > 
> > But, since alloca is already entrenched in gdb and available in liberty
> > I don't think this is an issue, is it?
> > 
> 
> Warning: if the "liberty" alloca() is used a "alloca(0)" must be added to
> our interpreter's command loops or the garbage collection becomes somewhat
> random (it will only happen when you call alloca() for allocating some
> other stuff and will only clean what was allocated by code that executed on frames
> below the current stack position.
> 
> I think we have this bug when alloca() gets used right now.
> 
> (Nothing difficult, we just need to remember to do it)

Note, that liberty's alloca will only be used if the host compiler is not GCC,
which probably makes it even harder to remember to use....  BTW, there are
systems out there that even's liberty's alloca will not work on (due to either
using a cactus stack or allocating the stack in pieces from the heap).

-- 
Michael Meissner, Red Hat, Inc.
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