pr: fix parsing of empty arguments

Before:
  $ pr --expand-tabs=
  pr: '-e' extra characters or invalid number in the argument:
   ‘SHELL=/bin/bash’: Value too large for defined data type

After:
  $ pr --expand-tabs=
  pr: '-e': Invalid argument: ‘’

* src/pr.c (getoptarg): Ensure we don't parse beyond the
end of an empty argument, thus outputting arbitrary stack
info in subsequent error messages.

Addresses https://bugs.debian.org/1035596

1 files changed, 6 insertions, 0 deletions

diff --git a/src/pr.c b/src/pr.c
index 14a368b6c..1c32e8c81 100644
--- a/src/pr.c
+++ b/src/pr.c
@@ -1168,6 +1168,12 @@ getoptnum (char const *n_str, int min, int *num, char const *err)
 static void
 getoptarg (char *arg, char switch_char, char *character, int *number)
 {
+  if (!*arg)
+    {
+      error (0, 0, _("'-%c': Invalid argument: %s"), switch_char, quote (arg));
+      usage (EXIT_FAILURE);
+    }
+
   if (!ISDIGIT (*arg))
     *character = *arg++;
   if (*arg)