On Fri, Dec 04, 2020 at 07:33:46AM -0800, Yang Zhong wrote:
> Yes, I've done something similar to that in my proof-of-concept.
> Instead of an extern, I made a function that opens /tmp and
> saves the fd.

Right, that's good. The idea with a global variable came about
when I tried to find ways which reduce the amount of diff created
for upstream code when tweaking function parameters to pass fds.

> Speaking of mkostempsat: I've been poking around my changes
> and it seems like many of them depend on mkostempsat, since
> I often change absolute paths to ones relative to fds. Right now
> I've written a stand-in opentemp function that (I think) does
> something equivalent, but it's certainly not something that I
> can actually commit.

An important point about absolute vs. relative paths:

Version control systems deal a lot with paths, and often have to
perform computations on paths such as splitting, appending, etc.

Like Subversion, Got tries to use only absolute paths internally.

In Subversion's case this is being enforced by error checking at the
library API level, such that passing relative paths becomes impossible.

Got's library is less strict, but the goal of most, if not all, realpath(3)
calls is to ensure that we're dealing in absolute paths. Some code will
probably misbehave if relative paths are passed around instead.

So if you can, please try to avoid switching to relative paths. If a
system call requires a relative path, it should generally be possible to
convert an absolute path into a relative one on demand. The opposite
conversion is difficult, hence the need for functions like realpath(3).