Merge pull request #257 from ethereum/cpp-host-call

cpp: Fix Host::call()

CHANGELOG.md

@@ -1,5 +1,13 @@
 # Changelog
 
+## [6.2.1] - unreleased
+
+- Fixed:
+  [[#256](https://github.com/ethereum/evmc/issues/256),
+  [#257](https://github.com/ethereum/evmc/issues/257)]
+  Disallow implicit conversion from C++ `evmc::result` to `evmc_result` 
+  causing unintendent premature releasing of resources. 
+
 ## [6.2.0] - 2019-04-25
 
 - Added: [[#216](https://github.com/ethereum/evmc/pull/216)]

circle.yml

@@ -66,12 +66,12 @@ jobs:
       CXX: g++-8
       CMAKE_OPTIONS: -DTOOLCHAIN=cxx17-pic
 
-  build-cxx14:
+  build-cxx14-asan:
     <<: *build
     environment:
       CC: clang-8
       CXX: clang++-8
-      CMAKE_OPTIONS: -DTOOLCHAIN=cxx14-pic
+      CMAKE_OPTIONS: -DTOOLCHAIN=cxx14-pic -DSANITIZE=address
 
   build-gcc6:
     <<: *build
@@ -178,7 +178,7 @@ workflows:
     jobs:
       - lint
       - build-cxx17
-      - build-cxx14
+      - build-cxx14-asan
       - build-gcc6
       - build-clang3.8
       - bindings-go-latest

examples/example_host.cpp

@@ -94,10 +94,14 @@ public:
 
     evmc::result call(const evmc_message& msg) noexcept final
     {
-        (void)msg;
         // TODO: Improve C++ API for result creation.
         evmc_result res{};
-        res.status_code = EVMC_FAILURE;
+        res.status_code = EVMC_REVERT;
+        auto output = new uint8_t[msg.input_size];
+        std::copy(&msg.input_data[0], &msg.input_data[msg.input_size], output);
+        res.output_size = msg.input_size;
+        res.output_data = output;
+        res.release = [](const evmc_result* r) noexcept { delete[] r->output_data; };
         return evmc::result{res};
     }
 

include/evmc/evmc.hpp

@@ -17,9 +17,15 @@ namespace evmc
 ///
 /// This is a RAII wrapper for evmc_result and objects of this type
 /// automatically release attached resources.
-class result : public evmc_result
+class result : private evmc_result
 {
 public:
+    using evmc_result::create_address;
+    using evmc_result::gas_left;
+    using evmc_result::output_data;
+    using evmc_result::output_size;
+    using evmc_result::status_code;
+
     /// Converting constructor from raw evmc_result.
     explicit result(evmc_result const& res) noexcept : evmc_result{res} {}
 
@@ -45,6 +51,15 @@ public:
         std::swap(*this, other);
         return *this;
     }
+
+    /// Returns the raw copy of evmc_result,
+    /// releases the ownership of the resources and invalidates this object.
+    evmc_result raw() noexcept
+    {
+        auto out = evmc_result{};
+        std::swap<evmc_result>(out, *this);
+        return out;
+    }
 };
 
 /// @copybrief evmc_instance
@@ -302,7 +317,7 @@ inline void selfdestruct(evmc_context* h,
 }
 inline evmc_result call(evmc_context* h, const evmc_message* msg) noexcept
 {
-    return static_cast<Host*>(h)->call(*msg);
+    return static_cast<Host*>(h)->call(*msg).raw();
 }
 inline evmc_tx_context get_tx_context(evmc_context* h) noexcept
 {

test/unittests/test_cpp.cpp

@@ -87,7 +87,6 @@ TEST(cpp, host)
     EXPECT_EQ(host.copy_code(a, 0, nullptr, 0), 0);
 
     host.selfdestruct(a, a);
-    EXPECT_EQ(host.call({}).gas_left, 0);
 
     auto tx = host.get_tx_context();
     EXPECT_EQ(host.get_tx_context().block_number, tx.block_number);
@@ -98,3 +97,26 @@ TEST(cpp, host)
 
     example_host_destroy_context(host_context);
 }
+
+TEST(cpp, host_call)
+{
+    // Use example host to test Host::call() method.
+
+    auto* host_context = example_host_create_context();
+    auto host = evmc::HostContext{host_context};
+
+    EXPECT_EQ(host.call({}).gas_left, 0);
+
+    auto msg = evmc_message{};
+    msg.gas = 1;
+    uint8_t input[] = {0xa, 0xb, 0xc};
+    msg.input_data = input;
+    msg.input_size = sizeof(input);
+
+    auto res = host.call(msg);
+    EXPECT_EQ(res.status_code, EVMC_REVERT);
+    EXPECT_EQ(res.output_size, msg.input_size);
+    EXPECT_TRUE(std::equal(&res.output_data[0], &res.output_data[res.output_size], msg.input_data));
+
+    example_host_destroy_context(host_context);
+}