[wasm] Fix decoding of shared global index space

src/wasm/wasm-module.cc

 // Copyright 2015 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 <memory>
 
 #include "src/base/atomic-utils.h"
 #include "src/code-stubs.h"
 
 #include "src/macro-assembler.h"
@@ skipping 1528 matching lines @@
       uint32_t dest_addr =
           static_cast<uint32_t>(segment->get_int(kDestAddrValue));
       if (segment->get_int(kDestAddrKind) == 1) {
         // The destination address is the value of a global variable.
         dest_addr =
             *reinterpret_cast<uint32_t*>(raw_buffer_ptr(globals, dest_addr));
       }
 
       uint32_t source_size =
           static_cast<uint32_t>(segment->get_int(kSourceSize));
+      // TODO(titzer): These should be runtime errors and not CHECKs if
+      // dest_addr is global (and therefore initialized at linktime to an
+      // possibly-invalid value).
       CHECK_LT(dest_addr, mem_size);
       CHECK_LE(source_size, mem_size);
       CHECK_LE(dest_addr, mem_size - source_size);
       byte* addr = mem_addr + dest_addr;
       data->copy_out(last_extraction_pos, addr, source_size);
       last_extraction_pos += source_size;
     }
   }
 
   Handle<Code> CompileImportWrapper(int index, Handle<FixedArray> data,
@@ skipping 719 matching lines @@
   WasmCompiledModule* compiled_module =
       WasmCompiledModule::cast(instance->GetInternalField(kWasmCompiledModule));
   CHECK(compiled_module->has_weak_module_object());
   CHECK(compiled_module->ptr_to_weak_module_object()->cleared());
 }
 
 }  // namespace testing
 }  // namespace wasm
 }  // namespace internal
 }  // namespace v8