From 8b9867c971e63885421e44a3464a67449131003d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Pawe=C5=82=20Bylica?= <chfast@gmail.com>
Date: Tue, 27 Sep 2016 17:14:19 +0200
Subject: [PATCH] EVM-C: Attach result_release function to the result itself

---
 examples/capi.c      |  2 +-
 examples/examplevm.c | 10 +++++-----
 include/evm.h        | 31 +++++++++++++++++++------------
 3 files changed, 25 insertions(+), 18 deletions(-)

diff --git a/examples/capi.c b/examples/capi.c
index cb66ee0..1499c36 100644
--- a/examples/capi.c
+++ b/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);
 }
diff --git a/examples/examplevm.c b/examples/examplevm.c
index 4569fa4..c000dd9 100644
--- a/examples/examplevm.c
+++ b/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;
 }
\ No newline at end of file
diff --git a/include/evm.h b/include/evm.h
index d3d9880..06d799c 100644
--- a/include/evm.h
+++ b/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.
@@ -83,6 +95,13 @@ struct evm_result {
     /// The error message explaining the result code.
     char const* error_message;
 
+    /// 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;
+
     /// @}
 };
 
@@ -370,15 +389,6 @@ 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 +437,6 @@ 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.