[LLVMdev] LLI Segfaulting

[Gavin Harrison]

Yes, that is what I mean. :-)
On Mar 12, 2012 11:02 AM, "Fraser Cormack" <frasercrmck at gmail.com> wrote:

>
> Hi Gavin,
>
> Do you mean something along the lines of having my array struct as { i32,
> i32* } and then indexing it with a gep and allocating the appropriate
> memory
> when I learn of it?
>
> Thanks,
> Fraser
>
>
> Gavin Harrison-2 wrote:
> >
> > Hi Fraser,
> >
> > Is there anything preventing you from using a pointer for the second part
> > of the structure and allocating memory for it later?
> >
> > Thanks,
> > Gavin
> >
> > On Mar 12, 2012, at 10:35 AM, Fraser Cormack wrote:
> >
> >>
> >> Hi Duncan,
> >>
> >>
> >> Duncan Sands wrote:
> >>>
> >>> Hi Fraser, it looks to me like you are smashing the stack.
> >>>
> >>>> define void @main() nounwind {
> >>>> allocas:
> >>>>   %0 = alloca { i32, [0 x i32] }, align 8
> >>>
> >>> ^ this allocates 4 bytes on the stack.
> >>>
> >>>>   %2 = getelementptr inbounds { i32, [0 x i32] }* %0, i64 0, i32 1
> >>>
> >>> ^ this gets a pointer to the byte after the 4 allocated bytes.
> >>>
> >>>>   %3 = bitcast [0 x i32]* %2 to i8*
> >>>>   call void @llvm.memcpy.p0i8.p0i8.i64(i8* %3, i8* bitcast ([5 x i32]*
> >>>> @.gvar_array to i8*), i64 20, i32 4, i1 false)
> >>>
> >>> This copies 20 bytes there, kaboom!
> >>>
> >>
> >> Such a painfully obvious answer, thank you! I'm assuming this is what
> >> happens when I use the unoptimized version of the code and call
> >>
> >>>   %0 = alloca %MainClass
> >>
> >> then transfer the array into that. If I'm taking a MainClass pointer
> into
> >> my
> >> <init> function, can I then just re-allocate it as a { i32, [5 x i32] }
> >> when
> >> I learn about the length? That doesn't sound like the nicest option. I'm
> >> not
> >> aware of a way of only allocating a part of a literal struct, is that
> >> possible?
> >>
> >> Cheers,
> >> Fraser
> >> --
> >> View this message in context:
> >> http://old.nabble.com/LLI-Segfaulting-tp33486161p33486962.html
> >> Sent from the LLVM - Dev mailing list archive at Nabble.com.
> >>
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> >
> >
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>
> --
> View this message in context:
> http://old.nabble.com/LLI-Segfaulting-tp33486161p33487147.html
> Sent from the LLVM - Dev mailing list archive at Nabble.com.
>
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