bug#7305: sort command not working in version 5.5 as it did in 4.7

[Paul Eggert]

On 11/17/10 14:33, Pádraig Brady wrote:

> Note it scans command line args twice which
> adds some overhead in all cases.
> The first scan is to find --debug so we're not
> dependent on the position of --debug

I have some qualms about that patch.  It's not just the extra overhead:
the patch causes --debug to change the semantics of argument processing
(as opposed to merely outputting debugging info), which could lead to
Heisenbugs.  "The script started working when I added --debug"
is a bug report that we never want to hear.

Also, if we want to suggest portable usage, it's better to suggest ./+FOO
rather than -- FOO, as the former is a bit shorter and works better with
pre-POSIX sorts.

How about something like the following patch instead, along with the obvious
changes to the test cases that you proposed?

diff --git a/src/sort.c b/src/sort.c
index 7e25f6a..86cd51c 100644
--- a/src/sort.c
+++ b/src/sort.c
@@ -3990,6 +3990,7 @@ main (int argc, char **argv)
   bool need_random = false;
   unsigned long int nthreads = 0;
   size_t nfiles = 0;
+  size_t unprotected_file_names = 0;
   bool posixly_correct = (getenv ("POSIXLY_CORRECT") != NULL);
   bool obsolete_usage = (posix2_version () < 200112);
   char **files;
@@ -4113,6 +4114,7 @@ main (int argc, char **argv)
           if (argc <= optind)
             break;
           files[nfiles++] = argv[optind++];
+          unprotected_file_names += (c != -1);
         }
       else switch (c)
         {
@@ -4165,7 +4167,10 @@ main (int argc, char **argv)
                 }
             }
           if (! key)
-            files[nfiles++] = optarg;
+            {
+              files[nfiles++] = optarg;
+              unprotected_file_names++;
+            }
           break;
 
         case SORT_OPTION:
@@ -4470,6 +4475,15 @@ main (int argc, char **argv)
                quote (setlocale (LC_COLLATE, NULL)));
       else
         error (0, 0, _("using simple byte comparison"));
+
+      for (size_t i = 0; i < unprotected_file_names; i++)
+        if (files[i][0] == '+')
+          {
+            char const *q = quotearg_style (shell_quoting_style, files[i]);
+            error (0, 0, _("Unportable file name %s; use ./%s instead"),
+                   q, q);
+          }
+
       key_warnings (&gkey, gkey_only);
     }