From 66b2ae96638782883e4d5543e56249918c9cd393 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Pawe=C5=82=20Bylica?= <chfast@gmail.com>
Date: Thu, 22 Dec 2016 12:55:49 +0100
Subject: [PATCH] EVM-C: return by explicit output param

In evm_query_fn, return result by explicit output parameter to avoid C ABI issues and inrease portability. C compiler would do the same implicitly.
---
 examples/capi.c | 20 +++++++++++---------
 include/evm.h   |  7 ++++---
 2 files changed, 15 insertions(+), 12 deletions(-)

diff --git a/examples/capi.c b/examples/capi.c
index f87e408..98a0e09 100644
--- a/examples/capi.c
+++ b/examples/capi.c
@@ -16,25 +16,27 @@ struct evm_uint160be address(struct evm_env* env)
     return ret;
 }
 
-static union evm_variant query(struct evm_env* env,
-                               enum evm_query_key key,
-                               const union evm_variant* arg) {
-    union evm_variant result;
+static void query(union evm_variant* result,
+                  struct evm_env* env,
+                  enum evm_query_key key,
+                  const union evm_variant* arg) {
     printf("EVM-C: QUERY %d\n", key);
     switch (key) {
-    case EVM_GAS_LIMIT: result.int64 = 314; break;
+    case EVM_GAS_LIMIT:
+        result->int64 = 314;
+        break;
 
     case EVM_BALANCE:
-        result.uint256be = balance(env, arg->address);
+        result->uint256be = balance(env, arg->address);
         break;
 
     case EVM_ADDRESS:
-        result.address = address(env);
+        result->address = address(env);
         break;
 
-    default: result.int64 = 0; break;
+    default:
+        result->int64 = 0;
     }
-    return result;
 }
 
 static void update(struct evm_env* env,
diff --git a/include/evm.h b/include/evm.h
index b97096f..8561a9a 100644
--- a/include/evm.h
+++ b/include/evm.h
@@ -229,9 +229,10 @@ union evm_variant {
 ///   @param arg evm_variant::uint256be  The index of the storage entry.
 ///   @result evm_variant::uint256be  The current value of the storage entry.
 ///
-typedef union evm_variant (*evm_query_fn)(struct evm_env* env,
-                                          enum evm_query_key key,
-                                          const union evm_variant* arg);
+typedef void (*evm_query_fn)(union evm_variant* result,
+                             struct evm_env* env,
+                             enum evm_query_key key,
+                             const union evm_variant* arg);
 
 /// The update callback key.
 enum evm_update_key {