Fix GCC warnings preventing build

-Wimplicit-fallthrough was added in newer versions of GCC.
"// fall through" is a special tag for letting GCC know that
a switch case fallthough is intentional.

-Wformat-truncation was added in newer versions of GCC.
Simply storing the return code of snprintf calls silences this.

src/request.c

@@ -1632,17 +1632,25 @@ S3Status request_api_initialize(const char *userAgentInfo, int flags,
 
     char platform[96];
     struct utsname utsn;
+    int snprintf_ret = 0;
     if (uname(&utsn)) {
-        snprintf(platform, sizeof(platform), "Unknown");
+        snprintf_ret = snprintf(platform, sizeof(platform), "Unknown");
     }
     else {
-        snprintf(platform, sizeof(platform), "%s%s%s", utsn.sysname, 
+        snprintf_ret = snprintf(platform, sizeof(platform), "%s%s%s", utsn.sysname, 
                  utsn.machine[0] ? " " : "", utsn.machine);
     }
 
-    snprintf(userAgentG, sizeof(userAgentG), 
+    if (snprintf_ret < 0) {
+        return S3StatusInternalError;
+    }
+
+    snprintf_ret = snprintf(userAgentG, sizeof(userAgentG), 
              "Mozilla/4.0 (Compatible; %s; libs3 %s.%s; %s)",
              userAgentInfo, LIBS3_VER_MAJOR, LIBS3_VER_MINOR, platform);
+    if (snprintf_ret < 0) {
+        return S3StatusInternalError;
+    }
 
     return S3StatusOK;
 }

src/util.c

@@ -485,16 +485,27 @@ uint64_t hash(const unsigned char *k, int length)
 
         switch(length) {
         case 12: c += ((uint32_t) k[11]) << 24;
+        // fall through
         case 11: c += ((uint32_t) k[10]) << 16;
+        // fall through
         case 10: c += ((uint32_t) k[9]) << 8;
+        // fall through
         case 9 : c += k[8];
+        // fall through
         case 8 : b += ((uint32_t) k[7]) << 24;
+        // fall through
         case 7 : b += ((uint32_t) k[6]) << 16;
+        // fall through
         case 6 : b += ((uint32_t) k[5]) << 8;
+        // fall through
         case 5 : b += k[4];
+        // fall through
         case 4 : a += ((uint32_t) k[3]) << 24;
+        // fall through
         case 3 : a += ((uint32_t) k[2]) << 16;
+        // fall through
         case 2 : a += ((uint32_t) k[1]) << 8;
+        // fall through
         case 1 : a += k[0]; break;
         case 0 : goto end;
         }
@@ -525,16 +536,27 @@ uint64_t hash(const unsigned char *k, int length)
 
         switch(length) {
         case 12: c += k[11];
+        // fall through
         case 11: c += ((uint32_t) k[10]) << 8;
+        // fall through
         case 10: c += ((uint32_t) k[9]) << 16;
+        // fall through
         case 9 : c += ((uint32_t) k[8]) << 24;
+        // fall through
         case 8 : b += k[7];
+        // fall through
         case 7 : b += ((uint32_t) k[6]) << 8;
+        // fall through
         case 6 : b += ((uint32_t) k[5]) << 16;
+        // fall through
         case 5 : b += ((uint32_t) k[4]) << 24;
+        // fall through
         case 4 : a += k[3];
+        // fall through
         case 3 : a += ((uint32_t) k[2]) << 8;
+        // fall through
         case 2 : a += ((uint32_t) k[1]) << 16;
+        // fall through
         case 1 : a += ((uint32_t) k[0]) << 24; break;
         case 0 : goto end;
         }