[wasm] improve handling of malformed input

test/unittests/wasm/leb-helper-unittest.cc

 // Copyright 2016 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "test/unittests/test-utils.h"
 
 #include "src/objects-inl.h"
 #include "src/wasm/decoder.h"
 #include "src/wasm/leb-helper.h"
 
@@ skipping 79 matching lines @@
 
 #define DECLARE_ENCODE_DECODE_CHECKER(ctype, name)                         \
   static void CheckEncodeDecode_##name(ctype val) {                        \
     static const int kSize = 16;                                           \
     static byte buffer[kSize];                                             \
     byte *ptr = buffer;                                                    \
     LEBHelper::write_##name(&ptr, val);                                    \
     EXPECT_EQ(LEBHelper::sizeof_##name(val),                               \
               static_cast<size_t>(ptr - buffer));                          \
     Decoder decoder(buffer, buffer + kSize);                               \
-    int length = 0;                                                        \
+    unsigned length = 0;                                                   \
     ctype result = decoder.checked_read_##name(buffer, 0, &length);        \
     EXPECT_EQ(val, result);                                                \
     EXPECT_EQ(LEBHelper::sizeof_##name(val), static_cast<size_t>(length)); \
   }
 
 DECLARE_ENCODE_DECODE_CHECKER(int32_t, i32v)
 DECLARE_ENCODE_DECODE_CHECKER(uint32_t, u32v)
 DECLARE_ENCODE_DECODE_CHECKER(int64_t, i64v)
 DECLARE_ENCODE_DECODE_CHECKER(uint64_t, u64v)
 
@@ skipping 71 matching lines @@
     CheckEncodeDecode_i64v(bit_cast<int64_t>(val));
   }
 
   for (uint64_t val = 0xFFFFFFFFFFFFFF3B; val != 0; val = val << 1) {
     CheckEncodeDecode_i64v(bit_cast<int64_t>(val));
   }
 }
 }  // namespace wasm
 }  // namespace internal
 }  // namespace v8