Add compiler flag -Wsign-compare

Also, fix the warnings generated by this flag.

Change-Id: I1dc6e61caa5d56af4a55b6692ab620bb3144652a

args.c

@@ -9,6 +9,7 @@
  * PATENTS file, you can obtain it at www.aomedia.org/license/patent.
  */
 
+#include <stdint.h>
 #include <stdlib.h>
 #include <string.h>
 #include <limits.h>
@@ -119,13 +120,13 @@ void arg_show_usage(FILE *fp, const struct arg_def *const *defs) {
 }
 
 unsigned int arg_parse_uint(const struct arg *arg) {
-  long int rawval;
+  uint32_t rawval;
   char *endptr;
 
-  rawval = strtol(arg->val, &endptr, 10);
+  rawval = strtoul(arg->val, &endptr, 10);
 
   if (arg->val[0] != '\0' && endptr[0] == '\0') {
-    if (rawval >= 0 && rawval <= UINT_MAX) return rawval;
+    if (rawval <= UINT_MAX) return rawval;
 
     die("Option %s: Value %ld out of range for unsigned int\n", arg->name,
         rawval);
@@ -136,7 +137,7 @@ unsigned int arg_parse_uint(const struct arg *arg) {
 }
 
 int arg_parse_int(const struct arg *arg) {
-  long int rawval;
+  int32_t rawval;
   char *endptr;
 
   rawval = strtol(arg->val, &endptr, 10);

configure

@@ -575,6 +575,7 @@ process_toolchain() {
         check_add_cflags -Wimplicit-function-declaration
         check_add_cflags -Wuninitialized
         check_add_cflags -Wunused-variable
+        check_add_cflags -Wsign-compare
         case ${CC} in
           *clang*)
               # libaom and/or clang have issues with aliasing:

examples/aom_cx_set_ref.c

@@ -296,7 +296,7 @@ int main(int argc, char **argv) {
   unsigned int frame_out = 0;
 
   // The frame number to set reference frame on
-  int update_frame_num = 0;
+  unsigned int update_frame_num = 0;
   int mismatch_seen = 0;
 
   const int fps = 30;
@@ -307,7 +307,8 @@ int main(int argc, char **argv) {
   const char *height_arg = NULL;
   const char *infile_arg = NULL;
   const char *outfile_arg = NULL;
-  int limit = 0;
+  const char *update_frame_num_arg = NULL;
+  unsigned int limit = 0;
   exec_name = argv[0];
 
   if (argc < 7) die("Invalid number of arguments");
@@ -317,18 +318,21 @@ int main(int argc, char **argv) {
   height_arg = argv[3];
   infile_arg = argv[4];
   outfile_arg = argv[5];
+  update_frame_num_arg = argv[6];
 
   encoder = get_aom_encoder_by_name(codec_arg);
   if (!encoder) die("Unsupported codec.");
 
-  update_frame_num = atoi(argv[6]);
+  update_frame_num = (unsigned int)strtoul(update_frame_num_arg, NULL, 0);
   // In AV1, the reference buffers (cm->buffer_pool->frame_bufs[i].buf) are
   // allocated while calling aom_codec_encode(), thus, setting reference for
   // 1st frame isn't supported.
-  if (update_frame_num <= 1) die("Couldn't parse frame number '%s'\n", argv[6]);
+  if (update_frame_num <= 1) {
+    die("Couldn't parse frame number '%s'\n", update_frame_num_arg);
+  }
 
   if (argc > 7) {
-    limit = atoi(argv[7]);
+    limit = (unsigned int)strtoul(argv[7], NULL, 0);
     if (update_frame_num > limit)
       die("Update frame number couldn't larger than limit\n");
   }