fix some warning

crack.c

@@ -20,11 +20,17 @@ int main(int argc, char** argv) {
         // record 30 passwords
         FILE* pwdfp;
         unsigned char buffer[SHA256_BLOCK_SIZE];
+        int status;
 
         pwdfp = fopen(PWD4_FILENAME, "rb");
 
         // read 32 bytes to buffer
-        fread(buffer, SHA256_BLOCK_SIZE, 1, pwdfp);
+        status = fread(buffer, SHA256_BLOCK_SIZE, 1, pwdfp);
+
+        if (status < 0) {
+            fprintf(stderr, "ERROR reading binary file\n");
+            exit(0);
+        }
 
         printf("%s", buffer);
 
@@ -54,7 +60,7 @@ int main(int argc, char** argv) {
 void check_guess(BYTE guess[], BYTE pwd[PWD_NUMBERS][SHA256_BLOCK_SIZE]) {
     SHA256_CTX ctx;
     BYTE buf[SHA256_BLOCK_SIZE];
-    size_t guess_len = strlen(guess);
+    size_t guess_len = strlen((char*)&guess);
     int i;
 
     sha256_init(&ctx);