GNU bug report logs - #23723
patch-shebang phase breaks symlinks

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: ludo <at> gnu.org (Ludovic Courtès)
Cc: tracker <at> debbugs.gnu.org
Subject: bug#23723: closed (patch-shebang phase breaks symlinks)
Date: Mon, 12 Sep 2016 19:39:02 +0000

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Your message dated Mon, 12 Sep 2016 21:37:55 +0200
with message-id <87lgywzz70.fsf <at> gnu.org>
and subject line Re: bug#23723: patch-shebang phase breaks symlinks
has caused the debbugs.gnu.org bug report #23723,
regarding patch-shebang phase breaks symlinks
to be marked as done.

(If you believe you have received this mail in error, please contact
help-debbugs <at> gnu.org.)


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23723: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=23723
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From: Jelle Licht <jlicht <at> fsfe.org>
To: bug-guix <at> gnu.org
Subject: patch-shebang phase breaks symlinks
Date: Wed, 08 Jun 2016 01:42:31 +0200

Hi Guix,

It seems that the patch-shebang functionality does not deal gracefully
with symlinks: it just overwrites them!

After struggling somewhat with getting the recently packaged node 6.0.0
to behave, I found out that `patch-shebang' in (guix build
gnu-build-system) does not work properly on symlinks.

To illustrate, in this specific case, there was an executable
script included with the node tarball, namely
`lib/node-modules/npm/bin/npm-cli.js' with an env-based shebang:
`/usr/bin/env node'.

As the `node' executable will only be available after the `install'
phase of the build system, it is not patched before hand. During the
`install' phase, a symlink is created from `bin/npm' to
`lib/node-modules/npm/bin/npm-cli.js' (in the store output directory
this time, of course). Then the `patch-shebangs' phase finds this
symlink and proceeds to patch it. Instead of transparently following the
symlink and patching the `npm-cli.js' script, the `npm' symlink is
overwritten with a shebang-patched copy of `npm-cli.js'.

For node, this is a problem because of how node loads run-time
dependencies; load paths are resolved relative to the actual file, not
the symlink.

- Jelle

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From: ludo <at> gnu.org (Ludovic Courtès)
To: Jelle Licht <jlicht <at> fsfe.org>
Cc: 23723-done <at> debbugs.gnu.org
Subject: Re: bug#23723: patch-shebang phase breaks symlinks
Date: Mon, 12 Sep 2016 21:37:55 +0200

ludo <at> gnu.org (Ludovic Courtès) skribis:

> Jelle Licht <jlicht <at> fsfe.org> skribis:

[...]

>> Also, seeing as my experience with the stat utility and similarly styled
>> programming libraries was lacking, I decided to play around with the
>> definition of `list-of-files': It actually does include symlinks, as
>> (stat:type (stat "some-symlinked-file")) gives us a plain old 'regular.
>> Looking into this a bit more, it seems that calling `stat' gives the
>> exact same results on both the linked-to-file and the symlink to that
>> file.
>>
>> For the particular problem I ran into to be fixed, it is imperative that
>> `list-of-files' of `patch-shebangs' includes the symlink; it does after
>> all need to be patched. The way this patching currently happens just
>> clobbers symlinks.
>
> My bad, indeed, ‘list-of-files’ should use ‘lstat’ instead of ‘stat’.

This was fixed some time ago in core-updates by commit
c13a9feb5b64fd819eaed38a17da0284bbe2b8d9; closing this bug!

Ludo’.

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