[huskerlug] Re: More of a GCC problem.
- From: <jwessels@xxxxxxxxxxxxxxxxxxx>
- To: <huskerlug@xxxxxxxxxxxxx>
- Date: Tue, 18 Mar 2003 11:30:23 -0700 (MST)
To allocate a dynamic array in C++ use:
x = blah;
int * myarray = new int[x]; // x must be 1 or greater
then to access the array like any other
myarray[y] = 0; // with y from 0 to x-1
To delete the array
delete [] myarray;
In C you must use malloc and typecast to your array type.
>
> Is there a reason you want to use a variable array? If not, use a
> #define to create a constant & use that in your array declaration. Or
> you could just use a literal.
>
> I think the link you gave said it all:
>
> (However, GCC's implementation of variable-length arrays does not
> yet conform in detail to the ISO C99 standard.)
>
> There is always more than one way to do something. Especially in a
> language as complex as C/C++.
>
> --Ben Chavet
>
>
> Quoting Jon Richardson <jonpaulrichardson@xxxxxxxxxxx>:
>
>>
>>
>>
>> Grr.... I'm fed up of buggy compilers, maybe it's just me? :) Anyways
>> I'm fairly new to gcc having ported my code from visual c++ 6.
>> (Although this code wasn't ported from visual c++ 6) I'm getting
>> some strange results from
>>
>> the output of my code.
>>
>> The variable iLabelNode is a variable sized array declared as such:
>>
>> int iBalance = 0;
>> int iLabelNode[iBalance];
>>
>> The variable iBalance later changes to a larger value.
>>
>> Here is the code where the problem occurs:
>>
>> puts("<------------- FlowGraph Crap -------------->");
>> for (UINT m = 1; m <= oListLabel.Count(); ++m)
>> {
>> printf("%s = %d\n", oListLabel.Value(m), iLabelNode[m
>> -
>> 1]);
>> }
>>
>> printf("iLabelNode[0] = %d\n", iLabelNode[0]);
>>
>> //get actual count
>> m_iNodeCount -= iBalance;
>>
>> printf("iLabelNode[0] = %d\n", iLabelNode[0]);
>>
>> //create nodes
>> Node* pNode = 0;
>> for (int y = 0; y < m_iNodeCount; ++y)
>> {
>> pNode = new Node;
>> pNodeArray[y] = pNode;
>> }
>> printf("iLabelNode[0] = %d\n", iLabelNode[0]); //<-- screw up
>> here
>>
>>
>> Can also be viewed here for pretty syntax highlighting :)
>> http://www.rafb.net/paste/results/P1014321.html
>>
>> PORTION OF OUTPUT
>> <------------- FlowGraph Crap -------------->
>> IL_0006: = 4
>> IL_000e: = 6
>> iLabelNode[0] = 4
>> iLabelNode[0] = 4
>> iLabelNode[0] = 134587360
>>
>> My question is why does the value of iLabelNode[0] change when it's
>> clearly
>>
>> not being modified? The funny thing is is that if I declare it as
>> such "int
>>
>> iLableNode[100]" it works fine. Should I just avoid variable sized
>> arrays?
>>
>> Am I doing something stupid I don't see?
>>
>> Here is what the gcc manual says about variable sized arrays, didn't
>> say much but maybe I'm missing something.
>> http://gcc.gnu.org/onlinedocs/gcc-3.2.2/gcc/Variable-Length.html#Variable%20Length
>>
>> If anyone could shed some light on this for me I would be very
>> thankful, this is driving me nuts.
>>
>> Thanks,
>>
>> Jon
>>
>>
>>
>>
>>
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>
>
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