Correctly relativize file names in the presence of common prefixes.

* libguile/filesys.c (scm_i_relativize_path): When DIR is a prefix of
SCANON, make sure DIR ends with a separator or SCANON starts with a
separator.
* test-suite/tests/ports.test (%temporary-directory): New variable.
("%file-port-name-canonicalization")["relative canonicalization with
common prefixes"]: New test.

2 files changed, 34 insertions, 2 deletions

diff --git a/libguile/filesys.c b/libguile/filesys.c
index f18560162..af283dd5e 100644
--- a/libguile/filesys.c
+++ b/libguile/filesys.c
@@ -1,5 +1,5 @@
 /* Copyright (C) 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2004, 2006,
- *   2009, 2010, 2011, 2012, 2013, 2014, 2016 Free Software Foundation, Inc.
+ *   2009, 2010, 2011, 2012, 2013, 2014, 2016, 2017 Free Software Foundation, Inc.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public License
@@ -1679,7 +1679,11 @@ scm_i_relativize_path (SCM path, SCM in_path)
       if (len > 0
 	  && scm_is_true (scm_string_prefix_p (dir, scanon,
 					       SCM_UNDEFINED, SCM_UNDEFINED,
-					       SCM_UNDEFINED, SCM_UNDEFINED)))
+					       SCM_UNDEFINED, SCM_UNDEFINED))
+
+	  /* Make sure SCANON starts with DIR followed by a separator.  */
+	  && (is_file_name_separator (scm_c_string_ref (dir, len - 1))
+	      || is_file_name_separator (scm_c_string_ref (scanon, len))))
 	{
 	  /* DIR either has a trailing delimiter or doesn't.  SCANON
 	     will be delimited by single delimiters.  When DIR does not
diff --git a/test-suite/tests/ports.test b/test-suite/tests/ports.test
index 007f56605..3c8ae3050 100644
--- a/test-suite/tests/ports.test
+++ b/test-suite/tests/ports.test
@@ -1890,6 +1890,10 @@
       (lambda ()
         (set! %load-path old)))))
 
+(define %temporary-directory
+  (string-append (or (getenv "TMPDIR") "/tmp") "/guile-ports-test."
+                 (number->string (getpid))))
+
 (with-test-prefix "%file-port-name-canonicalization"
 
   (pass-if-equal "absolute file name & empty %load-path entry" "/dev/null"
@@ -1916,6 +1920,30 @@
       (port-filename
        (open-input-file (%search-load-path "ice-9/q.scm")))))
 
+  (pass-if-equal "relative canonicalization with common prefixes"
+      "x.scm"
+
+    ;; In Guile up to 2.2.2, this would return "wrong/x.scm'.
+    (let* ((dir1 (string-append %temporary-directory "/something"))
+           (dir2 (string-append dir1 "-wrong")))
+      (with-load-path (append (list dir1 dir2) %load-path)
+        (dynamic-wind
+          (lambda ()
+            (mkdir %temporary-directory)
+            (mkdir dir1)
+            (mkdir dir2)
+            (call-with-output-file (string-append dir2 "/x.scm")
+              (const #t)))
+          (lambda ()
+            (with-fluids ((%file-port-name-canonicalization 'relative))
+              (port-filename
+               (open-input-file (string-append dir2 "/x.scm")))))
+          (lambda ()
+            (delete-file (string-append dir2 "/x.scm"))
+            (rmdir dir2)
+            (rmdir dir1)
+            (rmdir %temporary-directory))))))
+
   (pass-if-equal "absolute canonicalization from ice-9"
       (canonicalize-path
        (string-append (assoc-ref %guile-build-info 'top_srcdir)