[LLVMdev] LLI Segfaulting

[Gavin Harrison]

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
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> 
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