WebAssembly: skip unknown sections, add names

src/wasm/decoder.h

Index: src/wasm/decoder.h
diff --git a/src/wasm/decoder.h b/src/wasm/decoder.h
index 0e88eda022de439228b6f862098dff55376ae954..25d46b33f063e91af92381298a686819c8a28c03 100644
--- a/src/wasm/decoder.h
+++ b/src/wasm/decoder.h
@@ -222,10 +222,19 @@ class Decoder {
     return traceOffEnd<uint32_t>();
   }
 
+  // Consume {size} bytes and send them to the bit bucket, advancing {pc_}.
+  void consume_bytes(size_t size) {
+    if (checkAvailable(size)) {
+      pc_ += size;
+    } else {
+      pc_ = limit_;
+    }
+  }
+
   // Check that at least {size} bytes exist between {pc_} and {limit_}.
-  bool checkAvailable(int size) {
-    if (pc_ < start_ || (pc_ + size) > limit_) {
-      error(pc_, nullptr, "expected %d bytes, fell off end", size);
+  bool checkAvailable(size_t size) {
+    if (pc_ < start_ || (limit_ - start_) < size || limit_ < (pc_ + size)) {
+      error(pc_, nullptr, "expected %z bytes, fell off end", size);
       return false;
     } else {
       return true;