Merge pull request #101 from ethereum/evmc

EVM-C: Attach result_release function to the result itself

examples/capi.c

@@ -93,6 +93,6 @@ int main(int argc, char *argv[]) {
         printf("\n");
     }
 
-    intf.release_result(&result);
+    result.release(&result);
     intf.destroy(jit);
 }

examples/examplevm.c

@@ -40,6 +40,10 @@ int evm_set_option(struct evm_instance* evm,
     return 0;
 }
 
+static void evm_release_result(struct evm_result const* result)
+{
+}
+
 static struct evm_result evm_execute(struct evm_instance* instance,
                                      struct evm_env* env,
                                      enum evm_mode mode,
@@ -57,16 +61,13 @@ static struct evm_result evm_execute(struct evm_instance* instance,
 
     // Execute code and refer to callbacks: instance->query_fn()
 
+    ret.release = evm_release_result;
     ret.code = EVM_FAILURE;
     ret.gas_left = 0;
 
     return ret;
 }
 
-static void evm_release_result(struct evm_result const* result)
-{
-}
-
 struct evm_interface examplevm_get_interface()
 {
     struct evm_interface intf;
@@ -75,7 +76,6 @@ struct evm_interface examplevm_get_interface()
     intf.create = evm_create;
     intf.destroy = evm_destroy;
     intf.execute = evm_execute;
-    intf.release_result = evm_release_result;
     intf.set_option = evm_set_option;
     return intf;
 }

include/evm.h

@@ -55,6 +55,18 @@ enum evm_result_code {
     EVM_STACK_UNDERFLOW = 6,
 };
 
+struct evm_result;
+
+/// Releases resources assigned to an execution result.
+///
+/// This function releases memory (and other resources, if any) assigned to the
+/// specified execution result making the result object invalid.
+///
+/// @param result  The execution result which resource are to be released. The
+///                result itself it not modified by this function, but becomes
+///                invalid and user should discard it as well.
+typedef void (*evm_release_result_fn)(struct evm_result const* result);
+
 /// The EVM code execution result.
 struct evm_result {
     /// The execution result code.
@@ -65,24 +77,44 @@ struct evm_result {
     /// The value is valid only if evm_result::code == ::EVM_SUCCESS.
     int64_t gas_left;
 
-    /// The reference to output data. The memory containing the output data
-    /// is owned by EVM and is freed with evm_release_result_fn().
-    uint8_t const* output_data;
+    union
+    {
+        struct
+        {
+            /// The reference to output data. The memory containing the output
+            /// data is owned by EVM and is freed with evm_result::release().
+            uint8_t const* output_data;
 
-    /// The size of the output data.
-    size_t output_size;
+            /// The size of the output data.
+            size_t output_size;
+        };
+
+        /// The address of the successfully created contract.
+        ///
+        /// This field has valid value only if the evm_result comes from a
+        /// successful CREATE opcode execution
+        /// (i.e. evm_call_fn(..., EVM_CREATE, ...)).
+        struct evm_uint160be create_address;
+    };
+
+    /// The pointer to the result release implementation.
+    ///
+    /// This function pointer must be set by the VM implementation and works
+    /// similary to C++ virtual destructor. Attaching the releaser to the result
+    /// itself allows VM composition.
+    evm_release_result_fn release;
 
     /// @name Optional
     /// The optional information that EVM is not required to provide.
     /// @{
 
+    /// The error message explaining the result code.
+    char const* error_message;
+
     /// The pointer to EVM-owned memory. For EVM internal use.
     /// @see output_data.
     void* internal_memory;
 
-    /// The error message explaining the result code.
-    char const* error_message;
-
     /// @}
 };
 
@@ -370,15 +402,6 @@ typedef struct evm_result (*evm_execute_fn)(struct evm_instance* instance,
                                             size_t input_size,
                                             struct evm_uint256be value);
 
-/// Releases resources assigned to an execution result.
-///
-/// This function releases memory (and other resources, if any) assigned to the
-/// specified execution result making the result object invalid.
-///
-/// @param result  The execution result which resource are to be released. The
-///                result itself it not modified by this function, but becomes
-///                invalid and user should discard it as well.
-typedef void (*evm_release_result_fn)(struct evm_result const* result);
 
 /// Status of a code in VM. Useful for JIT-like implementations.
 enum evm_code_status {
@@ -427,9 +450,6 @@ struct evm_interface {
     /// Pointer to function execuing a code in a VM.
     evm_execute_fn execute;
 
-    /// Pointer to function releasing an execution result.
-    evm_release_result_fn release_result;
-
     /// Optional pointer to function returning a status of a code.
     ///
     /// If the VM does not support this feature the pointer can be NULL.