[wasm] improve handling of malformed input

src/wasm/ast-decoder.h

 // 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.
 
 #ifndef V8_WASM_AST_DECODER_H_
 #define V8_WASM_AST_DECODER_H_
 
 #include "src/signature.h"
 #include "src/wasm/decoder.h"
 #include "src/wasm/wasm-opcodes.h"
 #include "src/wasm/wasm-result.h"
 
 namespace v8 {
 namespace internal {
 
 class BitVector;  // forward declaration
 
 namespace compiler {  // external declarations from compiler.
 class WasmGraphBuilder;
 }
 
 namespace wasm {
 
 // Helpers for decoding different kinds of operands which follow bytecodes.
 struct LocalIndexOperand {
   uint32_t index;
   LocalType type;
-  int length;
+  unsigned int length;

[titzer, 2016/06/09 06:48:15]

You can just use "unsigned", which is short for "unsigned int".

 
   inline LocalIndexOperand(Decoder* decoder, const byte* pc) {
     index = decoder->checked_read_u32v(pc, 1, &length, "local index");
     type = kAstStmt;
   }
 };
 
 struct ImmI8Operand {
   int8_t value;
-  int length;
+  unsigned int length;
   inline ImmI8Operand(Decoder* decoder, const byte* pc) {
     value = bit_cast<int8_t>(decoder->checked_read_u8(pc, 1, "immi8"));
     length = 1;
   }
 };
 
 struct ImmI32Operand {
   int32_t value;
-  int length;
+  unsigned int length;
   inline ImmI32Operand(Decoder* decoder, const byte* pc) {
     value = decoder->checked_read_i32v(pc, 1, &length, "immi32");
   }
 };
 
 struct ImmI64Operand {
   int64_t value;
-  int length;
+  unsigned int length;
   inline ImmI64Operand(Decoder* decoder, const byte* pc) {
     value = decoder->checked_read_i64v(pc, 1, &length, "immi64");
   }
 };
 
 struct ImmF32Operand {
   float value;
-  int length;
+  unsigned int length;
   inline ImmF32Operand(Decoder* decoder, const byte* pc) {
     value = bit_cast<float>(decoder->checked_read_u32(pc, 1, "immf32"));
     length = 4;
   }
 };
 
 struct ImmF64Operand {
   double value;
-  int length;
+  unsigned int length;
   inline ImmF64Operand(Decoder* decoder, const byte* pc) {
     value = bit_cast<double>(decoder->checked_read_u64(pc, 1, "immf64"));
     length = 8;
   }
 };
 
 struct GlobalIndexOperand {
   uint32_t index;
   LocalType type;
   MachineType machine_type;
-  int length;
+  unsigned int length;
 
   inline GlobalIndexOperand(Decoder* decoder, const byte* pc) {
     index = decoder->checked_read_u32v(pc, 1, &length, "global index");
     type = kAstStmt;
     machine_type = MachineType::None();
   }
 };
 
 struct Control;
 struct BreakDepthOperand {
   uint32_t arity;
   uint32_t depth;
   Control* target;
-  int length;
+  unsigned int length;
   inline BreakDepthOperand(Decoder* decoder, const byte* pc) {
-    int len1 = 0;
-    int len2 = 0;
+    unsigned int len1 = 0;
+    unsigned int len2 = 0;
     arity = decoder->checked_read_u32v(pc, 1, &len1, "argument count");
     depth = decoder->checked_read_u32v(pc, 1 + len1, &len2, "break depth");
     length = len1 + len2;
     target = nullptr;
   }
 };
 
 struct CallIndirectOperand {
   uint32_t arity;
   uint32_t index;
   FunctionSig* sig;
-  int length;
+  unsigned int length;
   inline CallIndirectOperand(Decoder* decoder, const byte* pc) {
-    int len1 = 0;
-    int len2 = 0;
+    unsigned int len1 = 0;
+    unsigned int len2 = 0;
     arity = decoder->checked_read_u32v(pc, 1, &len1, "argument count");
     index = decoder->checked_read_u32v(pc, 1 + len1, &len2, "signature index");
     length = len1 + len2;
     sig = nullptr;
   }
 };
 
 struct CallFunctionOperand {
   uint32_t arity;
   uint32_t index;
   FunctionSig* sig;
-  int length;
+  unsigned int length;
   inline CallFunctionOperand(Decoder* decoder, const byte* pc) {
-    int len1 = 0;
-    int len2 = 0;
+    unsigned int len1 = 0;
+    unsigned int len2 = 0;
     arity = decoder->checked_read_u32v(pc, 1, &len1, "argument count");
     index = decoder->checked_read_u32v(pc, 1 + len1, &len2, "function index");
     length = len1 + len2;
     sig = nullptr;
   }
 };
 
 struct CallImportOperand {
   uint32_t arity;
   uint32_t index;
   FunctionSig* sig;
-  int length;
+  unsigned int length;
   inline CallImportOperand(Decoder* decoder, const byte* pc) {
-    int len1 = 0;
-    int len2 = 0;
+    unsigned int len1 = 0;
+    unsigned int len2 = 0;
     arity = decoder->checked_read_u32v(pc, 1, &len1, "argument count");
     index = decoder->checked_read_u32v(pc, 1 + len1, &len2, "import index");
     length = len1 + len2;
     sig = nullptr;
   }
 };
 
 struct BranchTableOperand {
   uint32_t arity;
   uint32_t table_count;
   const byte* table;
-  int length;
+  unsigned int length;
   inline BranchTableOperand(Decoder* decoder, const byte* pc) {
-    int len1 = 0;
-    int len2 = 0;
+    unsigned int len1 = 0;
+    unsigned int len2 = 0;
     arity = decoder->checked_read_u32v(pc, 1, &len1, "argument count");
     table_count =
         decoder->checked_read_u32v(pc, 1 + len1, &len2, "table count");
     length = len1 + len2 + (table_count + 1) * sizeof(uint32_t);
 
     uint32_t table_start = 1 + len1 + len2;
     if (decoder->check(pc, table_start, (table_count + 1) * sizeof(uint32_t),
                        "expected <table entries>")) {
       table = pc + table_start;
     } else {
       table = nullptr;
     }
   }
   inline uint32_t read_entry(Decoder* decoder, int i) {
     DCHECK(i >= 0 && static_cast<uint32_t>(i) <= table_count);
     return table ? decoder->read_u32(table + i * sizeof(uint32_t)) : 0;
   }
 };
 
 struct MemoryAccessOperand {
   uint32_t alignment;
   uint32_t offset;
-  int length;
+  unsigned int length;
   inline MemoryAccessOperand(Decoder* decoder, const byte* pc) {
-    int alignment_length;
+    unsigned int alignment_length;
     alignment =
         decoder->checked_read_u32v(pc, 1, &alignment_length, "alignment");
-    int offset_length;
+    unsigned int offset_length;
     offset = decoder->checked_read_u32v(pc, 1 + alignment_length,
                                         &offset_length, "offset");
     length = alignment_length + offset_length;
   }
 };
 
 struct ReturnArityOperand {
   uint32_t arity;
-  int length;
+  unsigned int length;
 
   inline ReturnArityOperand(Decoder* decoder, const byte* pc) {
     arity = decoder->checked_read_u32v(pc, 1, &length, "return count");
   }
 };
 
 typedef compiler::WasmGraphBuilder TFBuilder;
 struct ModuleEnv;  // forward declaration of module interface.
 
 // All of the various data structures necessary to decode a function body.
@@ skipping 47 matching lines @@
   // Constructor initializes the vector.
   explicit AstLocalDecls(Zone* zone)
       : decls_encoded_size(0), total_local_count(0), local_types(zone) {}
 };
 
 bool DecodeLocalDecls(AstLocalDecls& decls, const byte* start, const byte* end);
 BitVector* AnalyzeLoopAssignmentForTesting(Zone* zone, size_t num_locals,
                                            const byte* start, const byte* end);
 
 // Computes the length of the opcode at the given address.
-int OpcodeLength(const byte* pc, const byte* end);
+unsigned int OpcodeLength(const byte* pc, const byte* end);
 
 // Computes the arity (number of sub-nodes) of the opcode at the given address.
-int OpcodeArity(const byte* pc, const byte* end);
+unsigned int OpcodeArity(const byte* pc, const byte* end);
 
 }  // namespace wasm
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_WASM_AST_DECODER_H_