bug#30006: bzip2 does not provide libbz2.so

[Marius Bakke <mbakke@fastmail.com>]

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Ludovic Courtès <ludo@gnu.org> writes:

> There’s no such function, which is unfortunate.  But I agree it’s nicer
> to preserve symlinks in this case.
>
> Perhaps we should actually do:
>
>   (with-directory-excursion libdir
>     (symlink … "libbz2.so"))

Thanks for the feedback everyone.  I settled on a slightly different
solution, that first extracts the (full) soversion from the built
library, then creates symlinks for each "sub-version".

It assumes that the major version is "1".  That could be circumvented
with a regex, but I'm not sure if it's worth the effort.

As an added bonus, this also creates "libbz2.so.1" which was missing too.

WDYT of this approach?  Can it be made simpler?


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From 6c903b1da1ab64c4f52581c7debb82b65a6afb0e Mon Sep 17 00:00:00 2001
From: Marius Bakke <mbakke@fastmail.com>
Date: Mon, 26 Mar 2018 19:24:59 +0200
Subject: [PATCH] gnu: bzip2: Provide libbz2.so and libbz2.so.1.

Fixes <https://bugs.gnu.org/30006>.

* gnu/packages/compression.scm (bzip2)[arguments]: Rework
INSTALL-SHARED-LIBS-PHASE to manage all library symlinks.
---
 gnu/packages/compression.scm | 31 ++++++++++++++++++++++---------
 1 file changed, 22 insertions(+), 9 deletions(-)

diff --git a/gnu/packages/compression.scm b/gnu/packages/compression.scm
index 3bcc09bd3..7c853e432 100644
--- a/gnu/packages/compression.scm
+++ b/gnu/packages/compression.scm
@@ -271,15 +271,28 @@ file; as a result, it is often used in conjunction with \"tar\", resulting in
          (add-after 'install 'install-shared-lib
            (lambda* (#:key outputs #:allow-other-keys)
              (let* ((out    (assoc-ref outputs "out"))
-                    (libdir (string-append out "/lib")))
-               (for-each (lambda (file)
-                           (let ((base (basename file)))
-                             (format #t "installing `~a' to `~a'~%"
-                                     base libdir)
-                             (copy-file file
-                                        (string-append libdir "/" base))))
-                         (find-files "." "^libbz2\\.so")))
-             #t))
+                    (libdir (string-append out "/lib"))
+                    ;; Find the actual library (e.g. "libbz2.so.1.0.6").
+                    (lib (string-drop
+                          (car (find-files
+                                "."
+                                (lambda (file stat)
+                                  (and (string-prefix? "./libbz2.so.1" file)
+                                       (eq? 'regular (stat:type stat))))))
+                          2))
+                    (soversion (string-drop lib (string-length "libbz2.so."))))
+               ;; The Makefile above does not have an 'install' target, nor
+               ;; does it create the versioned symlinks, so we handle it here.
+               (install-file lib libdir)
+               (with-directory-excursion libdir
+                 (let ((libs (string-split soversion #\.))
+                       (base "libbz2.so"))
+                   (map (lambda (so)
+                          (let ((next (string-append base "." so)))
+                            (symlink next base)
+                            (set! base next)))
+                        libs)))
+               #t)))
          (add-after 'install-shared-lib 'patch-scripts
            (lambda* (#:key outputs inputs #:allow-other-keys)
              (let* ((out (assoc-ref outputs "out")))
-- 
2.16.2


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