Fix error message of createSymbolicLink.

[nh2]

Consider ln (or any other Unix tool):

$ ln -s file1 file2
$ ls -l file2
lrwxrwxrwx 1 niklas niklas 5 Feb  8 03:09 file2 -> file1
$ ln -s file1 file2
ln: failed to create symbolic link 'file2': File exists

The file name mentioned in the error ("link2") is the one
that could not be created, not the content of the pointer.

createSymbolicLink got this wrong so far, it would print

file1: createSymbolicLink: already exists (File exists)

which is wrong, this file doesn't already exist.

This commit fixes it.

[glguy]

This seems like a reasonable change. Consulting the man page for symlink(2) on macOS I note that it's only in the case of EFAULT that file1 might be the relevant filename: [EFAULT] Path1 or path2 points outside the process's allocated address space. In all other cases the error message pertains to path2.

[nh2]

points outside the process's allocated address space

@glguy do you know what this means in the context of file systems? I'm trying to trigger this, but don't know how.

[nh2]

@glguy I just wanted to implement a check or EFAULT to address this, but then noticed that indeed it says Path1 or path2 so we can't really know which one it is.

So EFAULT seems to be unbiases about whether to include the first or second one in the message.

[rwbarton]

EFAULT means that one of the char *s you passed points to a memory address that isn't mapped in the application. For example, it is likely to happen if you pass a totally random char * value to symlink(). You'll have some trouble triggering it via createSymbolicLink; I wouldn't worry about the error message.

[nh2]

Ah, that makes sense, thanks for the explanation.