Created attachment 221499 [details]
patch to fix diff bug

When diff hits certain access errors, function diffreg() shows the error message, and then returns to the calling function, which calls print_status() with the return value.

However, in these cases, the return value isn't changed from the initial default value of D_SAME.

Normally, print_status() with a value of D_SAME does nothing, so this works out ok, however, if the "-s" flag is set, a message is displayed showing identicality:

case D_SAME:
                if (sflag)
                        printf("Files %s%s and %s%s are identical\n",                                                                                                       path1, entry, path2, entry);
                break;

This then produces such results as:

% diff  -s /COPYRIGHT /var/run/rpcbind.sock
diff: /var/run/rpcbind.sock: Operation not supported
Files /COPYRIGHT and /var/run/rpcbind.sock are identical

% diff  -s /COPYRIGHT /etc/master.passwd
diff: /etc/master.passwd: Permission denied
Files /COPYRIGHT and /etc/master.passwd are identical

A quick fix would be to alter the above line:

   if (sflag)

to

   if (sflag && status & 2)

A less hacky fix is attached as a patch. It creates a D_ERROR status which is returned in such cases, and print_status() then deals with that status seperately from D_SAME.