From 8c6718ab91416a1f60a9dfbacb867dfc03688adb Mon Sep 17 00:00:00 2001
From: Svyatoslav Scherbina <svyatoslav.scherbina@jetbrains.com>
Date: Thu, 11 May 2017 11:27:14 +0300
Subject: [PATCH] Always use at least register-sized buffer for return value in
 ffi_call

As required by the libffi docs.
---
 .../native/kotlin/kotlinx/cinterop/Varargs.kt  | 18 ++++++++++++++++++
 .../native/interop/gen/jvm/StubGenerator.kt    |  3 ++-
 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/Interop/Runtime/src/native/kotlin/kotlinx/cinterop/Varargs.kt b/Interop/Runtime/src/native/kotlin/kotlinx/cinterop/Varargs.kt
index 271e4866c48..3593284bfa9 100644
--- a/Interop/Runtime/src/native/kotlin/kotlinx/cinterop/Varargs.kt
+++ b/Interop/Runtime/src/native/kotlin/kotlinx/cinterop/Varargs.kt
@@ -69,6 +69,24 @@ private tailrec fun convertArgument(
     else -> throw Error("unsupported argument: $argument")
 }
 
+inline fun <reified T  : CVariable> NativePlacement.allocFfiReturnValueBuffer(type: CVariable.Type): T {
+    var size = type.size
+    var align = type.align
+
+    // libffi requires return value buffer to be no smaller than system register size;
+    // TODO: system register size is not exactly the same as pointer size.
+
+    if (size < pointerSize) {
+        size = pointerSize.toLong()
+    }
+
+    if (align < pointerSize) {
+        align = pointerSize
+    }
+
+    return this.alloc(size, align).reinterpret<T>()
+}
+
 fun callWithVarargs(codePtr: NativePtr, returnValuePtr: NativePtr, returnTypeKind: FfiTypeKind,
                     fixedArguments: Array<out Any?>, variadicArguments: Array<out Any?>,
                     argumentsPlacement: NativePlacement) {
diff --git a/Interop/StubGenerator/src/main/kotlin/org/jetbrains/kotlin/native/interop/gen/jvm/StubGenerator.kt b/Interop/StubGenerator/src/main/kotlin/org/jetbrains/kotlin/native/interop/gen/jvm/StubGenerator.kt
index bbc656f017d..ff0daa5b428 100644
--- a/Interop/StubGenerator/src/main/kotlin/org/jetbrains/kotlin/native/interop/gen/jvm/StubGenerator.kt
+++ b/Interop/StubGenerator/src/main/kotlin/org/jetbrains/kotlin/native/interop/gen/jvm/StubGenerator.kt
@@ -891,7 +891,8 @@ class StubGenerator(
             val returnValueMirror = mirror(func.returnType)
             block(header) {
                 val resultPtr = if (!func.returnsVoid()) {
-                    out("val resultVar = alloc<${returnValueMirror.pointedTypeName}>()")
+                    val returnType = returnValueMirror.pointedTypeName
+                    out("val resultVar = allocFfiReturnValueBuffer<$returnType>($returnType)")
                     "resultVar.rawPtr"
                 } else {
                     "nativeNullPtr"