GNU patch not completely posix compliant in --posix mode

[Adrian Bunk]

Hi Paul,

Peter Maydell <address@hidden> sent the following report:


<--  snip  -->

The POSIX specs for the patch utility say:
 (POSIX 2, page 588, section 5.22.7.2, part (1))
# If the patch contains the strings *** and ---, the patch utility shall
# strip components from the beginning of each pathname (depending on the
# presence or value of the -p option), then test for the existence of
# both files in the current directory (or the directory specified by
# the -d option). If both files exist, the patch utility shall assume
# that no pathname can be obtained from this step.

However, GNU patch (with --posix specified) will use the --- (OLD)
name even if both old and new files exist; that is, it's not following
the last sentence of the quoted paragraph.

Here's a patch against 2.5.4 which fixes this. It doesn't attempt
to modify the non-posix mode behaviour at all (which I think is
perverse, but hey (see also PR 49481).

hope this helps
Peter Maydell

===begin===
--- pch.c.orig  Thu Nov 29 16:19:02 2001
+++ pch.c       Thu Nov 29 16:29:13 2001
@@ -497,6 +497,8 @@
         Consider the file names to be in the order (old, new, index).
        - If some named files exist, use the first one if posixly_correct
         is nonzero, the best one otherwise.
+       - Exception: if posixly_correct and both old and new files exist
+        then they should both be ignored
        - If patch_get is nonzero, and no named files exist,
         but an RCS or SCCS master file exists,
         use the first named file with an RCS or SCCS master.
@@ -532,13 +534,25 @@
              else if (stat (name[i], &st[i]) != 0)
                stat_errno[i] = errno;
              else
-               {
-                 stat_errno[i] = 0;
-                 if (posixly_correct)
-                   break;
-               }
+               stat_errno[i] = 0;
+
              i0 = i;
            }
+
+       if (posixly_correct)
+         {
+           /* Take the first existing entry in (old, new, index), with the
+            * exception that if old and new both specify files which exist
+            * then we should assume that no pathnames were given for old
+            * and new. [See IEEE Std. 1003.2-1992 section 5.22.7.2 part (1)]
+            */
+           i = OLD;
+           if (name[OLD] && name[NEW] && !stat_errno[OLD] && !stat_errno[NEW])
+             i = INDEX;
+           for ( ; i <= INDEX; i++)
+             if (name[i] && !stat_errno[i])
+               break;
+         }

        if (! posixly_correct)
          {
===endit===

===begin===
--- patch.man.orig      Thu Nov 29 16:47:01 2001
+++ patch.man   Thu Nov 29 16:53:01 2001
@@ -177,9 +177,17 @@
 selects a file name from the candidate list as follows:
 .TP 3
 .B " \(bu"
+If
+.B patch
+is conforming to \s-1POSIX\s0,
+and the old and new names both name files which exist,
+then patch will ignore both old and new names (as if
+the patch file had never specified them).
+.TP
+.B " \(bu"
 If some of the named files exist,
 .B patch
-selects the first name if conforming to \s-1POSIX\s0,
+selects the first existing name if conforming to \s-1POSIX\s0,
 and the best name otherwise.
 .TP
 .B " \(bu"
===endit===

<--  snip  -->


cu
Adrian

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