maint: accommodate gcc's -Wstrict-overflow option

* src/factor.c (factor_using_pollard_rho): Change type of "i"
to unsigned to avoid warning from gcc's -Wstrict-overflow.
* src/expr.c: Use an unsigned intermediate.
* src/dircolors.c (main): Reorder operations to avoid the risk of
pointer overflow.
* src/tr.c (squeeze_filter): Change NOT_A_CHAR from an anonymous
"enum" to an "int", to avoid this warning:
tr.c:1624:10: error: assuming signed overflow does not occur when
  simplifying conditional to constant [-Werror=strict-overflow]
* src/pr.c (main): Make index "i" unsigned.

1 files changed, 5 insertions, 3 deletions

diff --git a/src/expr.c b/src/expr.c
index ce65ecf46..2331f64fe 100644
--- a/src/expr.c
+++ b/src/expr.c
@@ -312,15 +312,17 @@ main (int argc, char **argv)
 
   parse_long_options (argc, argv, PROGRAM_NAME, PACKAGE_NAME, VERSION,
                       usage, AUTHORS, (char const *) NULL);
+
   /* The above handles --help and --version.
      Since there is no other invocation of getopt, handle `--' here.  */
-  if (argc > 1 && STREQ (argv[1], "--"))
+  unsigned int u_argc = argc;
+  if (1 < u_argc && STREQ (argv[1], "--"))
     {
-      --argc;
+      --u_argc;
       ++argv;
     }
 
-  if (argc <= 1)
+  if (u_argc <= 1)
     {
       error (0, 0, _("missing operand"));
       usage (EXPR_INVALID);