Remove various compilation warnings

With the removal of these warnings we slightly improve the robustness of
the highscore parsing, handling some more cases of bad parsing/writing
and failure to open files.

Makefile

@@ -1,5 +1,5 @@
 CC      ?= clang
-CFLAGS  += -Wno-visibility -Wno-incompatible-pointer-types -Wall -Wextra -O2 -DINVERT_COLORS -DVT100
+CFLAGS  += -Wno-visibility -Wno-incompatible-pointer-types -Wall -Wextra -O2 -DINVERT_COLORS -DVT100 -O2
 LFLAGS  +=
 
 PROGRAM := 2048

src/engine.h

@@ -2,7 +2,6 @@
 #define ENGINE_H
 
 #include <stdio.h>
-#include "gfx.h"
 #include "options.h"
 
 #define fatal(msg)\
@@ -34,6 +33,8 @@ enum {
     dir_up
 };
 
+struct gfx_state;
+
 int gamestate_end_condition(struct gamestate*);
 void gamestate_new_block(struct gamestate*);
 int  gamestate_tick(struct gfx_state*, struct gamestate*, int, void (*callback)(struct gfx_state*, struct gamestate*));

src/highscore.c

@@ -57,7 +57,9 @@ void highscore_reset(void)
 
     while (1) {
         /* fgets is used to avoid queuing that may occur with getchar */
-        fgets(resp, resp_length, stdin);
+        if (fgets(resp, resp_length, stdin) == NULL)
+            return;
+
         string_to_lower(resp);
 
         const size_t sl = strlen(resp);
@@ -87,7 +89,16 @@ long highscore_load(struct gamestate *g)
     if (fd == NULL)
         fd = fopen(hsfile, "w+");
 
-    fscanf(fd, "%ld", &result);
+    if (fd == NULL) {
+        fprintf(stderr, "load: Failed to open highscore file\n");
+        return 0;
+    }
+
+    if (fscanf(fd, "%ld", &result) != 1) {
+        fprintf(stderr, "load: Failed to parse highscore file\n");
+        result = 0;
+    }
+
     fclose(fd);
 
     if (g) g->score_high = result;
@@ -105,6 +116,13 @@ void highscore_save(struct gamestate *g)
     const char *hsfile = highscore_retrieve_file();
 
     FILE *fd = fopen(hsfile, "w");
-    fprintf(fd, "%ld", g->score);
+    if (fd == NULL) {
+        fprintf(stderr, "save: Failed to open highscore file\n");
+        return;
+    }
+
+    if (fprintf(fd, "%ld", g->score) < 0) {
+        fprintf(stderr, "save: Failed to write highscore file\n");
+    }
     fclose(fd);
 }

src/highscore.h

@@ -1,6 +1,8 @@
 #ifndef HIGHSCORE_H
 #define HIGHSCORE_H
 
+#include "engine.h"
+
 void highscore_reset(void);
 long highscore_load(struct gamestate *g);
 void highscore_save(struct gamestate *g);

src/main.c

@@ -14,7 +14,7 @@ void draw_then_sleep(struct gfx_state *s, struct gamestate *g)
 int main(int argc, char **argv)
 {
     struct gamestate *g = gamestate_init(argc, argv);
-    struct gfx_state *s;
+    struct gfx_state *s = NULL;
 
     if (g->opts->interactive)
         s = gfx_init(g);