Ticket #12108: filesystem_canonical_bug.cpp

#include <iostream>
#include <boost/filesystem.hpp>

using boost::filesystem::path;
using std::cout;
using std::endl;
using std::ofstream;


int main(int argc, char** argv) {
        // Creates a directory symlink-example/dir containing a file hello.txt
        path tmp = boost::filesystem::temp_directory_path() / "symlink-example";
        boost::filesystem::remove_all(tmp);
        path myDir = tmp / "dir";
        boost::filesystem::create_directories(myDir);
        path myFile = myDir / "hello.txt";
        {
                ofstream filestream(myFile.string().c_str(), ofstream::out);
                filestream << "hello, world!" << endl;
        }

        // Creates a directory symlink symlink-example/sym -> symlink-example/dir
        path mySym = tmp / "sym";
        boost::filesystem::create_directory_symlink(myDir, mySym);

        // when cwd is a directory, c: is not considered a symlink and canonical works
        boost::filesystem::current_path(myDir);
        cout << "c: is symlink? " << boost::filesystem::is_symlink(path("c:")) << endl; // outputs 0
        boost::filesystem::canonical(myFile);

        // when cwd is the symlink to the directory, "c:" is considered a symlink to dir!
        boost::filesystem::current_path(mySym);
        cout << "c: is symlink? " << boost::filesystem::is_symlink(path("c:")) << endl; // outputs 1

        /*
        Canonical will enter an infinite loop. By way of example, assume 
                myDir  = c:\temp\symlink-example\dir
                mySym  = c:\temp\symlink-example\sym -> myDir
                myFile = c:\temp\symlink-example\dir\hello.txt
        It iterates over the path components of myFile (operations.cpp:827), starting with c:
        c: is considered a symlink (operations.cpp:844) with target myDir, so it expands it to
                c:\temp\symlink-example\dir\temp\symlink-example\dir\hello.txt
        scan is set true and the loop repeats, resulting in
                c:\temp\symlink-example\dir\temp\symlink-example\dir\temp\symlink-example\dir\hello.txt
        and so on in an infinite loop resulting in an infinitely expanding path.
        */
        boost::filesystem::canonical(myFile);
}