Your code should work as long as [font=courier new,courier,monospace]someotherfunction[/font] takes a [font=courier new,courier,monospace]const char*[/font].

If the problem is that it takes a [font=courier new,courier,monospace]char*[/font] (but does promise not to write to the buffer), then you can use the const-correctness hack:someotherfunction( const_cast<char*>(data->c_str()) );//C++ style
someotherfunction( (char*)(data->c_str()) );//or C-style casting