[Bug c++/51352] New: g++ can't pass variable-length array as a function argument

[jvgreen at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51352

             Bug #: 51352
           Summary: g++ can't pass variable-length array as a function
                    argument
    Classification: Unclassified
           Product: gcc
           Version: 4.6.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: jvgreen@gmail.com


According to http://gcc.gnu.org/onlinedocs/gcc/Variable-Length.html, gcc
supports variable-length arrays as an extension when compiling C++ code.  An
example is given on that page of how to pass such an array as an argument to a
function.  However, I haven't been able to get it to work.  As an example, the
simple program

  #include <iostream>
  #include <cstdlib>

  void fill_array(int dim, int array[dim][dim]);

  int main(int argc, char *const argv[]) {
    int dim = atoi(argv[1]);
    int array[dim][dim];
    fill_array(dim, array);
    for(int i = 0; i < dim; ++i) {
      for(int j = 0; j < dim; ++j) {
        std::cout << array[i][j] << "\n";
      }
    }
  }

  void fill_array(int dim, int array[dim][dim]) {
    int counter = 0;
    for(int i = 0; i < dim; ++i) {
      for(int j = 0; j < dim; ++j) {
        array[i][j] = counter++;
      }
    }
  }

won't compile under g++ version 4.6.1 (I think that's the version I was
running), despite what that page claims, instead giving errors claiming that
the parameter dim is being used outside the function.  (gcc in C99 mode can
compile the code.)