We used the create_symlink function in order to make a filesystem entry point to another file in the filesystem. This way we can avoid having duplicate files. We could also have set a hard link using create_hard_link. Semantically, this is similar, but hard links have other technical implications than soft links. Different filesystem formats might not support hard links at all, or only a certain number of hard links that refer to the same file. Another problem is that hard links cannot link from one filesystem to the other.

However, apart from implementation details, there is one blatant error source when using create_symlink or create_hard_link. The following lines contain a bug. Can you spot it immediately?

path a {"some_dir/some_file.txt"};
path b {"other_dir/other_file.txt"};
remove(b);
create_symlink(a, b);

Nothing bad happens when executing this program, but the symlink will be broken. The symlink points to "some_dir/some_file.txt", which is wrong. The problem is that it should really either point to "/absolute/path/some_dir/some_file.txt", or "../some_dir/some_file.txt". The create_symlink call uses a correct absolute path if we write it as follows:

create_symlink(absolute(a), b);