Question

I have function whose signature is something like so:

void someFunc(ifstream ifile) { 

This function is embedded deep within the code. When I am debugging this code with ddd, how can I get the name of the file from the ifstream object. Trying the following:
p ifile or

ptype ifile  

leads to a mountain of information being dumped. Is there a way to get the filename that ifile is a stream to?

Thanks,
Sriram.

Answer 1

Is there a way to get the filename that ifile is a stream to?

No way. That’s not possible.

std::ifstream doesn’t store the filename, neither does it provide any get function to get the filename. Thus, you cannot get it, given an object of type std::ifstream.

---

If you really need to know the filename inside the function (and cannot change the function signature), then you can maintain a global lookup table (or preferably std::map) and add an entry whenever you open a file, something like this:

std::map<std::ifstream*, const char*> g_stream_file_pairs;

std::ifstream ifile("xyz/abc/filename.txt");
g_stream_file_pairs.insert(std::make_pair(&ifile, ""xyz/abc/filename.txt"));


void someFunc(std::ifstream & ifile) 
{ 
       const char* filename = g_stream_file_pairs[&ifile];
       //...
}