From 6a2fb145963ff8242469b41bbe3acd9f6e16dec4 Mon Sep 17 00:00:00 2001
From: Stefan Monnier <monnier@iro.umontreal.ca>
Date: Thu, 30 Jun 2011 23:15:02 -0400
Subject: [PATCH] * lisp/emacs-lisp/find-func.el (find-library--load-name): New
 fun. (find-library-name): Use it to find relative load names when provided
 absolute file name.

Fixes: debbugs:8803
---
 lisp/ChangeLog               |  8 +++++++-
 lisp/emacs-lisp/find-func.el | 21 ++++++++++++++++++++-
 2 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index 1ce1eb61f14..68a492311fb 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,9 @@
+2011-07-01  Stefan Monnier  <monnier@iro.umontreal.ca>
+
+	* emacs-lisp/find-func.el (find-library--load-name): New fun.
+	(find-library-name): Use it to find relative load names when provided
+	absolute file name (bug#8803).
+
 2011-06-30  Lars Magne Ingebrigtsen  <larsi@gnus.org>
 
 	* textmodes/flyspell.el (flyspell-word): Consider words that
@@ -14,7 +20,7 @@
 
 	* progmodes/cc-guess.el: New file.
 
-	* progmodes/cc-langs.el (c-mode-menu): Added "Style..." submenu.
+	* progmodes/cc-langs.el (c-mode-menu): Add "Style..." submenu.
 
 	* progmodes/cc-styles.el (cc-choose-style-for-mode): New function
 	derived from `c-basic-common-init'.
diff --git a/lisp/emacs-lisp/find-func.el b/lisp/emacs-lisp/find-func.el
index 9c4a3e9832c..0194af2e3a8 100644
--- a/lisp/emacs-lisp/find-func.el
+++ b/lisp/emacs-lisp/find-func.el
@@ -141,6 +141,15 @@ See the functions `find-function' and `find-variable'."
     (dolist (suffix (get-load-suffixes) (nreverse suffixes))
       (unless (string-match "elc" suffix) (push suffix suffixes)))))
 
+(defun find-library--load-name (library)
+  (let ((name library))
+    (dolist (dir load-path)
+      (let ((rel (file-relative-name library dir)))
+        (if (and (not (string-match "\\`\\.\\./" rel))
+                 (< (length rel) (length name)))
+            (setq name rel))))
+    (unless (equal name library) name)))
+
 (defun find-library-name (library)
   "Return the absolute file name of the Emacs Lisp source of LIBRARY.
 LIBRARY should be a string (the name of the library)."
@@ -148,13 +157,23 @@ LIBRARY should be a string (the name of the library)."
   ;; the same name.
   (if (string-match "\\.el\\(c\\(\\..*\\)?\\)\\'" library)
       (setq library (replace-match "" t t library)))
-  (or 
+  (or
    (locate-file library
 		(or find-function-source-path load-path)
 		(find-library-suffixes))
    (locate-file library
 		(or find-function-source-path load-path)
 		load-file-rep-suffixes)
+   (when (file-name-absolute-p library)
+     (let ((rel (find-library--load-name library)))
+       (when rel
+         (or
+          (locate-file rel
+                       (or find-function-source-path load-path)
+                       (find-library-suffixes))
+          (locate-file rel
+                       (or find-function-source-path load-path)
+                       load-file-rep-suffixes)))))
    (error "Can't find library %s" library)))
 
 (defvar find-function-C-source-directory
-- 
2.39.2