Analitza's use of C99 variable-length arrays

[Percy Camilo Triveño Aucahuasi]

On Tue, Jul 1, 2014 at 5:39 AM, Aleix Pol <aleixpol at kde.org> wrote:

> On Tue, Jul 1, 2014 at 5:03 AM, Nicolás Alvarez <nicolas.alvarez at gmail.com
> > wrote:
>
>> Hi peeps,
>>
>> In analitza/commands/blockmatrixcommands.cpp, there is a variable-length
>> array:
>>
>> const int firstVectorSize = firstVector->size();
>> int blockpattern[firstVectorSize];
>>
>> This is a new feature in C99. The GCC manual says: "Variable-length
>> automatic arrays are allowed in ISO C99, and as an extension GCC
>> accepts them in C90 mode and in C++."
>>
>> MSVC doesn't support VLAs, at least not in C++ mode. And given the
>> above quote, it seems it's non-portable to use it in C++ anyway, so
>> (this time :P) we can't blame it on MSVC not being standards-compliant
>> or something.
>>
>> I replaced it with this to make it compile:
>> std::unique_ptr<int[]> blockpattern(new int[firstVectorSize]);
>>
>> But I don't know if this is acceptable (can I use C++11 in analitza?).
>> ##c++ told me to just use
>> std::vector<int> blockpattern(firstVectorSize, 0);
>>
>> which is a reasonable option, but it feels weird to use a std::vector
>> for something that won't be resized.
>>
>> I welcome thoughts from someone who actually knows the Analitza code :)
>>
>>
> Hi,
> Wouldn't that fix the issue?
>
> Aleix
>
> diff --git analitza/commands/blockmatrixcommands.cpp
> analitza/commands/blockmatrixcommands.cpp
> index 6ff20ef..568fbde 100644
> --- analitza/commands/blockmatrixcommands.cpp
> +++ analitza/commands/blockmatrixcommands.cpp
> @@ -62,7 +62,7 @@ Expression BlockMatrixCommand::operator()(const QList<
> Analitza::Expression >& a
>   bool isCorrect = true; // this flag tells if is ok to build the block
> matrix
>   int nrows = 0;
>   int ncols = 0;
> - int blockpattern[firstVectorSize]; // if vectors(matrixrow) this tells
> the row(column) pattern
> + std::vector<int> blockpattern(firstVectorSize, 0); // if
> vectors(matrixrow) this tells the row(column) pattern
>
>   const int blocklength = isVector? firstBlock->columnCount() :
> firstBlock->rowCount();
>
>
>
>
Hi Nicolás,

Please confirm us if the fix provided by Aleix is enough, I remember I did
some test with that approach (using std::vector) and it works ok ... even
more, I'm a bit surprised I left the code with a raw C99 array instead of
std::vector ... :p

Thanks ;)
Percy
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