Re: int array[N]; when N is not a constant
In article <Xns99A451F4D2315jgreerdoubletakecom@194.177.96.78>,
Joe Greer <jgreer@doubletake.com> wrote:
James Kanze <james.kanze@gmail.com> wrote in
news:1189164583.899629.70330@r29g2000hsg.googlegroups.com:
On Sep 6, 10:17 pm, Szabolcs <szhor...@gmail.com> wrote:
Is the following legal?
void fun(int N) {
int arr[N];
}
gcc and Digital Mars accept it, but msvc complains that it
wants a constant expression.
Have you invoked gcc as a C++ compiler (g++ -std=c++98
-pedantic), or as a C compiler (or as a C++ compiler with
extensions)? I get an error with g++ 4.1.0.
Anyway, it's legal C, but in C++, we'd write:
void
fun( int N )
{
std::vector< int > arr( N ) ;
}
Of course, they aren't exactly the same since (as I understand it)
int arr[N];
is totally on the stack whereas
std::vector<int> arr(N);
has a small piece on the stack and the array itself is on the heap.
Normally this isn't a problem, but it is a difference.
Although VLAs might normally be done on the stack,
there is no such requirement. For instance, Comeau C99 allows
for a stack model and a heap model to exist, depending upon
the implementation and options used, etc.
--
Greg Comeau / 4.3.9 with C++0xisms now in beta!
Comeau C/C++ ONLINE ==> http://www.comeaucomputing.com/tryitout
World Class Compilers: Breathtaking C++, Amazing C99, Fabulous C90.
Comeau C/C++ with Dinkumware's Libraries... Have you tried it?