Re: diffutils: suggested patch for --dontfollow (symlinks when recursing) option

[Denis Excoffier]

Hello,

Similar patch as in the previous message, except that (when the option  
is
set) the symlinks are kept undeferenced in all situations, not only in
case of directories. Don't apply both patches!

Option name `--no-dereference' (shortopt `-K') is preferred to
`--dontfollow' for consistency with the similar options in coreutils.

diffutils-2.8.7.tar.gz to be found under http://alpha.gnu.org/gnu/diffutils/



-----------------------------------------------------------
diff -rub diffutils-2.8.7.original/src/diff.c  
diffutils-2.8.7.nodereference/src/diff.c
--- diffutils-2.8.7.original/src/diff.c 2004-04-12 09:44:13 +0200
+++ diffutils-2.8.7.nodereference/src/diff.c    2009-03-24 22:16:57 +0100
@@ -66,6 +66,9 @@
    recursively.  */
 static bool recursive;

+/* In case of symlinks, use the contents, not the target */
+static bool no_dereference = false;
+
 /* In context diffs, show previous lines that match these regexps.  */
 static struct regexp_list function_regexp_list;

@@ -137,7 +140,7 @@
 }
 
 static char const shortopts[] =
-"0123456789abBcC:dD:eEfF:hHiI:lL:nNpPqrsS:tTuU:vwW:x:X:y";
+"0123456789abBcC:dD:eEfF:hHiI:KlL:nNpPqrsS:tTuU:vwW:x:X:y";

 /* Values for long options that do not have single-letter  
equivalents.  */
 enum
@@ -216,6 +219,7 @@
   {"new-file", 0, 0, 'N'},
   {"new-group-format", 1, 0, NEW_GROUP_FORMAT_OPTION},
   {"new-line-format", 1, 0, NEW_LINE_FORMAT_OPTION},
+  {"no-dereference", 0, 0, 'K'},
   {"no-ignore-file-name-case", 0, 0, NO_IGNORE_FILE_NAME_CASE_OPTION},
   {"normal", 0, 0, NORMAL_OPTION},
   {"old-group-format", 1, 0, OLD_GROUP_FORMAT_OPTION},
@@ -400,6 +404,10 @@
          add_regexp (&ignore_regexp_list, optarg);
          break;

+        case 'K':
+          no_dereference = true;
+          break;
+
        case 'l':
          if (!pr_program[0])
            try_help ("pagination not supported on this host", 0);
@@ -913,6 +921,7 @@
   "",
   N_("-r  --recursive  Recursively compare any subdirectories  
found."),
   N_("-N  --new-file  Treat absent files as empty."),
+  N_("-K  --no-dereference  Don't follow symlinks (elsewhere  
undocumented)."),
   N_("--unidirectional-new-file  Treat absent first files as empty."),
   N_("-s  --report-identical-files  Report when two files are the  
same."),
   N_("-x PAT  --exclude=PAT  Exclude files that match PAT."),
@@ -1125,8 +1134,12 @@
                  set_mtime_to_now (&cmp.file[f].stat);
                }
            }
-         else if (stat (cmp.file[f].name, &cmp.file[f].stat) != 0)
+         else {
+            int (*stat_action)(char const *, struct stat *) =  
no_dereference ? lstat : stat;
+            if (stat_action(cmp.file[f].name, &cmp.file[f].stat) !=  
0) {
            cmp.file[f].desc = ERRNO_ENCODE (errno);
+            };
+          };
        }
     }

@@ -1206,6 +1219,36 @@
       /* The two named files are actually the same physical file.
         We know they are identical without actually reading them.  */
     }
+#define LNK_P(f) (S_ISLNK (cmp.file[f].stat.st_mode) != 0)
+  else if (no_dereference && (LNK_P(0) || LNK_P(1))) {
+      /* no_dereference is here only for clarity since S_ISLNK can  
show up
+      only under lstat(), never under stat() */
+      bool they_differ = true;
+      if (LNK_P(0) && LNK_P(1)) {
+        char linkpath0[PATH_MAX];
+        char linkpath1[PATH_MAX];
+        int nbc0, nbc1;
+        if ((nbc0 = readlink(cmp.file[0].name, linkpath0,  
sizeof(linkpath0))) == -1) {
+          perror_with_name(cmp.file[0].name);
+          status = EXIT_TROUBLE;
+        } else {
+          if ((nbc1 = readlink(cmp.file[1].name, linkpath1,  
sizeof(linkpath1))) == -1) {
+            perror_with_name(cmp.file[1].name);
+            status = EXIT_TROUBLE;
+          } else {
+            if ((nbc0 == nbc1) && !strncmp(linkpath0, linkpath1,  
nbc0)) {
+              they_differ = false;
+            };
+          };
+        };
+      };
+      if (they_differ && (status == EXIT_SUCCESS)) {
+        message("Files %s and %s differ\n",
+           file_label[0] ? file_label[0] : cmp.file[0].name,
+           file_label[1] ? file_label[1] : cmp.file[1].name);
+        status = EXIT_FAILURE;
+      };
+    }
   else if (DIR_P (0) & DIR_P (1))
     {
       if (output_style == OUTPUT_IFDEF)
-----------------------------------------------------------


Denis Excoffier.