Re: PATCH: 3.1.6-test-1: strange cd behaviour

[Peter Stephenson <pws@ibmth.df.unipi.it>]

Peter Stephenson wrote:
> (Although with AUTOCD `../rod' on its own already fails,
> because it tests for a physical directory, since cancd() doesn't call
> fixdir() --- anyone want that fixed?)
> 
> It's now true that if you do `cd bar/../rod' and bar is a symlink, then
> this won't work because of the test I added --- it stat's bar/../rod which
> looks for rod in the physical parent of the directory to which bar points.
> Maybe this is already going too far when CHASELINKS is unset.  (I could
> change it to stat every occurrence of <dir>/.. , which was my first thought,
> and which should get round this.)

Fixing the first of these bugs seems to be easy, just an extra call to
fixdir() with pwd tacked on front if necessary, so I did it.

Looking at the second one, I realised my response to Andrej's suggestion
was excessive.  By only testing the directories which really need to be
there --- e.g. in the case of foo/bar/../rod/.., that would be foo/bar,
then foo/rod when we wipe out the bar/.. bit --- we can both have a
reliable test for real directories, and also not bother whether or not
we're in pwd, since we're always looking only at the already modified
directory string which has to exist.

So this code is very much simpler than what I proposed before, and also has
the feature Andrej suggested, that `cd ..' might as well fail if the
directory doesn't exist, since ... well, since the directory doesn't
exist.  You can do ${PWD:h} to get to the parent.  Most of the patch is
removing what I just added.

--- Src/builtin.c.cd2	Thu Jul 15 17:21:44 1999
+++ Src/builtin.c	Thu Jul 15 17:40:15 1999
@@ -1042,44 +1042,13 @@
  * combinations, are removed and the path is unmetafied.   */
 
 /**/
-static void
+void
 fixdir(char *src)
 {
-    char *dest = src, *d0 = dest, *chks = src, *ptrp;
+    char *dest = src, *d0 = dest;
 #ifdef __CYGWIN
     char *s0 = src;
 #endif
-    int donecheck = 0, len;
-
-    /*
-     * Normally, we should not rationalize away path segments foo/.. if
-     * the directory foo does not exist.  However, if foo was part of
-     * pwd then we should allow it, because we know the current
-     * directory was once valid, although may have been deleted, and `cd
-     * ..' should always work as long as the parent directory exists.
-     * Hence we find an initial portion of the path consisting of pwd
-     * followed by any number of .. or . segments, and don't check
-     * that the original path exists.  After this point (given by
-     * chks), if there are any remaining ..'s in the path we
-     * check that the directory with the remaining portion
-     * unrationalized really exists, and return if it doesn't.
-     *
-     * Bug:  this is ridiculously heavy handed.
-     */
-    len = strlen(pwd);
-    if (!strncmp(src, pwd, len) && src[len] == '/') {
-	chks = src + len;
-	while (*chks == '/')
-	    chks++;
-	while (*chks == '.' &&
-	       (!chks[1] || chks[1] == '/' ||
-		(chks[1] == '.' && (!chks[2] || chks[2] == '/')))) {
-	    while (*chks == '.')
-		chks++;
-	    while (*chks == '/')
-		chks++;
-	}
-    }
 
 /*** if have RFS superroot directory ***/
 #ifdef HAVE_SUPERROOT
@@ -1115,33 +1084,21 @@
 	}
 	if (src[0] == '.' && src[1] == '.' &&
 	  (src[2] == '\0' || src[2] == '/')) {
-	    if (!donecheck && src >= chks) {
+	    if (dest > d0 + 1) {
 		/*
-		 * We need to check the original path exists, to catch
-		 * problems like 'cd nonexistent/..'.  We use dest
-		 * as far as we've got, plus the rest of src.
-		 * We only need to do this once, as any later ..'s
-		 * will automatically be tested here.
+		 * remove a foo/.. combination:
+		 * first check foo exists, else return
 		 */
 		struct stat st;
-		char *testdir;
-		if (dest == src)
-		    testdir = dupstring(d0);
-		else {
-		    *dest = '\0';
-		    testdir = dyncat(d0, src);
-		}
-		for (chks = src, ptrp = testdir + (dest - d0); *chks;
-		     chks++, ptrp++)
-		    *ptrp = (*chks == Meta) ? (*++chks ^ 32) : *chks;
-		if (stat(testdir, &st) < 0 || !S_ISDIR(st.st_mode)) {
-		    strcpy(d0, testdir);
+		*dest = '\0';
+		if (stat(d0, &st) < 0 || !S_ISDIR(st.st_mode)) {
+		    char *ptrd, *ptrs;
+		    if (dest == src)
+			*dest = '.';
+		    for (ptrs = src, ptrd = dest; *ptrs; ptrs++, ptrd++)
+			*ptrd = (*ptrs == Meta) ? (*++ptrs ^ 32) : *ptrs;
 		    return;
 		}
-		donecheck = 1;
-	    }
-	    if (dest > d0 + 1) {
-		/* remove a foo/.. combination */
 		for (dest--; dest > d0 + 1 && dest[-1] != '/'; dest--);
 		if (dest[-1] != '/')
 		    dest--;
--- Src/exec.c.cd2	Thu Jul  8 17:10:17 1999
+++ Src/exec.c	Thu Jul 15 17:40:01 1999
@@ -3144,9 +3144,16 @@
 cancd2(char *s)
 {
     struct stat buf;
-    char *us = unmeta(s);
+    char *us = unmeta(s), *us2 = NULL;
 
+    if (*us != '/')
+	us = us2 = tricat(unmeta(pwd), "/", us);
+    else
+	us = dupstring(us);
+    fixdir(us);
     return !(access(us, X_OK) || stat(us, &buf) || !S_ISDIR(buf.st_mode));
+    if (us2)
+	zsfree(us2);
 }
 
 /**/

-- 
Peter Stephenson <pws@ibmth.df.unipi.it>       Tel: +39 050 844536
WWW:  http://www.ifh.de/~pws/
Dipartimento di Fisica, Via Buonarroti 2, 56127 Pisa, Italy