Using auto_ptr object

Question

I need to store my error and log messages to the file. This is the code sample:

#include <fstream>
#include <iostream>
#include <memory>

int main()
{
    std::auto_ptr<std::ofstream> cerrFile;

    try {
        std::ofstream* a;
        a = new std::ofstream("c:\\Development\\_Projects\\CERR_LOG.txt");
        cerrFile.reset(a);
        a = NULL;

        std::cout << cerrFile.get() << std::endl << a;
        std::cerr.rdbuf(cerrFile->rdbuf());
    }
    catch (const std::exception& e) {
        std::cerr << "error: " << e.what();
    }

    // ...

    cerrFile.get()->close(); // ???
}

If I defined cerrFile as a global variable, would be it released correctly? Need I close the log file before exit like with a regular pointer?

Don't use `auto_ptr`, which never really worked right and is deprecated. Use `std::unique_ptr`, which replaces it. — aschepler, Dec 18 '19 at 05:53
`auto_ptr` has been deprecated since C++11 and was removed from the standard library in C++17. Since C++11 there is `std::unique_ptr` replacing it and before it you are probably better of with `boost::scoped_ptr` or some other boost smart pointer (or yet better by upgrading to a recent C++ version). — walnut, Dec 18 '19 at 06:19
You also don't need a pointer here at all, from what I can tell. Just declare `std::ofstream a;` and use `a = std::ofstream(...); `, which also works since C++11 or `a.open(...)` which always worked. — walnut, Dec 18 '19 at 06:23

score 1 · Answer 1 · answered Dec 18 '19 at 09:20

1

In your sample, you don't need to close the file.

When auto_ptr<std::ofstream> cerrFile; goes out of scope, the destructor of the contained object will be called. In this case, the destructor of std::ofstream which will close the file.

answered Dec 18 '19 at 09:20

foolo

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score 1 · Accepted Answer · answered Dec 18 '19 at 11:44

1

You don't need to close the file. When auto_ptr go out of scope call the destructor that close the file if not close.

Annotation: Please avoid use of std::auto_ptr because is deprecated in c++11 and completely removed in c++17.

answered Dec 18 '19 at 11:44

Zig Razor

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Using auto_ptr object

2 Answers2