bug#33893: [PATCH v5 2/4] gnu: Add docker-engine.

["Ludovic Courtès" <ludo@gnu.org>]

Howdy!

Danny Milosavljevic <dannym@scratchpost.org> skribis:

> On Tue, 08 Jan 2019 09:42:14 +0100
> Ludovic Courtès <ludo@gnu.org> wrote:
>
>> > Go has peculiar ideas of how the directory layout is supposed to be set up.
>> > I could probably figure it out - but if someone with more Go knowledge could
>> > step forward it would be much faster.  
>> 
>> I see Leo is Cc’d so we’ll see.  :-)
>
> Nevermind, I've fixed it and learned something in the process:
>
> Linux doesn't actually know the current working directory as a string.
> It only knows the inode, so if you call getcwd, what libc actually does is
> it opendirs "..", then finds the entry with the same inode number as
> the current directory, and then returns the name of that entry.

Are you sure?  In the Linux port of glibc I see this:

--8<---------------cut here---------------start------------->8---
char *
__getcwd (char *buf, size_t size)
{
  char *path;
  char *result;

  // […]

  retval = INLINE_SYSCALL (getcwd, 2, path, alloc_size);
--8<---------------cut here---------------end--------------->8---

And indeed, there’s a ‘getcwd’ syscall:

--8<---------------cut here---------------start------------->8---
$ strace -e getcwd guile -c '(getcwd)'
getcwd("/home/ludo", 100)               = 11
+++ exited with 0 +++
--8<---------------cut here---------------end--------------->8---

> Now, gopath uses symlinks to set up their preferred directory hierarchy
> in such a way:
>
> ln -s ../../../.. .gopath/src/github.com/docker/docker
>
> Now if you chdir into ".gopath/src/github.com/docker/docker" and then Go later
> does getcwd, it will appear as if the chdir did not succeed (because it will
> just use the old working directory because it has the same inode).
>
> So Go was erroring out because the directory structure there was *still* wrong.
>
> Solution: Set environment variable PWD to the correct name of the directory.

Great that you found a solution.

Thanks for taking the time to address this!

Ludo’.