Calling GDALOpen from a function

Question

I'm trying to call GDALOpen from a function to open a tiff raster and then use the dataset further in my main or other functions. This is the code I have so far:

int main( int argc, char* argv[] ){
GDALAllRegister();
GDALDataset *poRasterDataset;
openRaster(poRasterDataset, argv[1]);
...}

void openRaster(GDALDataset * poDataset, char* rasterName){
poDataset = (GDALDataset *) GDALOpen(rasterName, GA_ReadOnly);
...
}

My problem is if I do it this way my program crashes because it finds the poRasterDataset to be empty in main after calling openRaster, but if I call GDALOpen from main I have no problem using the dataset. I'm not very experienced in C++ but I suppose it has to do with how I'm passing poDataset in main after calling openRaster.

Answer 1

This might help you, it's from working code:

char* Raster = new char[FullPathMax];
wcstombs(Raster,argv[2],FullPathMax);
GDALAllRegister();
GDALDataset* SourceRasterDS = (GDALDataset*) GDALOpen(Raster,GA_ReadOnly);

So there's nothing wrong with your implementation per se. The problem with your code is that in your code block:

GDALDataset *poRasterDataset;
openRaster(poRasterDataset, argv[1]);

C++ wont let you assign pointers inside a function, you don't actually pass the pointer but pass the pointers' value, have a read of https://stackoverflow.com/questions/416162/assignment-inside-function-that-is-passed-as-pointer for more info. Consider:

int main( int argc, char* argv[] ){
GDALAllRegister();
GDALDataset *poRasterDataset = openRaster(argv[1]);
...}

GDALDataset* openRaster(char* rasterName){
GDALDataset poDataset = (GDALDataset *) GDALOpen(rasterName, GA_ReadOnly);
return poDataset;
}

As an alternative. Also, be aware that argv[1] isn't necessarily a char*, it could be a _TCHAR* which doesn't work with GDALOpen, hence I've used wcstombs (safer version wcstombs_s) to convert the _TCHAR pointer to char(byte) pointer.