Why does my CImg<float> have negative width and height?

Question

CImg<float>* img = NULL;
bool loaded;

while ( !loaded )
{
    loaded = true;
    try
    {
        img = &CImg<float>( filename );
    }
    catch ( CImgException )
    {
        loaded = false;
        fprintf( stdout, "ERROR: could not load %smap file.\n", mapname );
    }
}

When I enter a valid image filename that CImg is able to find and read, img.width() and img.height() both return -858993460. According to the documentation, img.width()'s return type is int, but the value if fetches is img._width, an unsigned int.

Answer 1

As GManNickG mentioned in the comment, at line img = &CImg<float>( filename ); temporary object of type CImg<float> created and you stores it's address into img variable. This temporary object is only valid inside the block:

try
{
  img = &CImg<float>( filename );
}

It's destructed when execution leaves this scope and you've got invalid pointer with some random content (e.g. -858993460 in _width field).