Tcl Source Code

The following TCL command:

file copy -force in.txt out.txt

will produce this call to "open" syscall:

open("out.txt", O_WRONLY|O_CREAT|O_TRUNC, 0100664) = 6

We can see that beside the mode ("664") there is the S_IFREG flag (0100000, regular flag) which is set. According to open man page, there shouldn't be any other bit in "mode" than the permission bits (see http://man7.org/linux/man-pages/man2/open.2.html "According to POSIX, the effect when other bits are set in mode is unspecified...")

I found that some filesystem doesn't like this bit to be set.

I see that "file copy -force" do a stat on the file before doing the open and I suspect TCL to blindly reuse the flag gained by the stat command but it should only use the lower bits.

We certainly shouldn't be setting the file type descriptor bits. There's literally no reason at all for handing those over.

I would say that we can keep all bits in the 07777 mask. Upper bits are informative bits for stat command.

It shouldn't break anything.

What do you think ?

> I suspect TCL to blindly reuse the flag gained by the stat command but it should only use the lower bits.

This appears to be the case:

  http://core.tcl.tk/tcl/artifact/1b60acbf412a1ef8?ln=574

This looks like the right place to mask the permissions parameter, but we should be careful.  To quote more fully from the Linux manual:

> According to POSIX, the effect when other bits (than 0777) are set in
> mode is unspecified.  On Linux, the following bits are also honored in
> mode:

(refers to mode & 07000 - setu/gid and sticky bits).

Should [file copy] on Linux also copy these bits?  What about other unixes?

This smells like one of those dusty under-specified corners of POSIX where
the right thing for all platforms is not always going to be obvious.