Add basic support for variable-length array parameters in cinterop (#2666)

Interop/Indexer/src/main/kotlin/org/jetbrains/kotlin/native/interop/indexer/Indexer.kt

@@ -522,14 +522,19 @@ internal class NativeIndexImpl(val library: NativeLibrary, val verbose: Boolean
             }
 
             CXType_ConstantArray -> {
-                val elemType = convertType(clang_getArrayElementType(type))
+                val elementType = convertType(clang_getArrayElementType(type))
                 val length = clang_getArraySize(type)
-                ConstArrayType(elemType, length)
+                ConstArrayType(elementType, length)
             }
 
             CXType_IncompleteArray -> {
-                val elemType = convertType(clang_getArrayElementType(type))
-                IncompleteArrayType(elemType)
+                val elementType = convertType(clang_getArrayElementType(type))
+                IncompleteArrayType(elementType)
+            }
+
+            CXType_VariableArray -> {
+                val elementType = convertType(clang_getArrayElementType(type))
+                VariableArrayType(elementType)
             }
 
             CXType_FunctionProto -> {

Interop/Indexer/src/main/kotlin/org/jetbrains/kotlin/native/interop/indexer/NativeIndex.kt

@@ -266,6 +266,7 @@ interface ArrayType : Type {
 
 data class ConstArrayType(override val elemType: Type, val length: Long) : ArrayType
 data class IncompleteArrayType(override val elemType: Type) : ArrayType
+data class VariableArrayType(override val elemType: Type) : ArrayType
 
 data class Typedef(val def: TypedefDef) : Type
 

backend.native/tests/interop/basics/ctypes.def

@@ -13,4 +13,39 @@ struct StructWithConstFields getStructWithConstFields() {
 enum ForwardDeclaredEnum;
 enum ForwardDeclaredEnum {
     ZERO, ONE, TWO
-};
+};
+
+static int vlaSum(int size, int array[size]) {
+    int result = 0;
+    for (int i = 0; i < size; ++i) {
+        result += array[i];
+    }
+    return result;
+}
+
+static int vlaSum2D(int size, int array[][size]) {
+    int result = 0;
+    for (int i = 0; i < size; ++i) {
+        for (int j = 0; j < size; ++j) {
+            result += array[i][j];
+        }
+    }
+    return result;
+}
+
+static int vlaSum2DBothDimensions(int rows, int columns, int array[rows][columns]) {
+    int result = 0;
+    for (int i = 0; i < rows; ++i) {
+        for (int j = 0; j < columns; ++j) {
+            result += array[i][j];
+        }
+    }
+    return result;
+}
+
+/*
+// Not supported by clang:
+static int vlaSum2DForward(int size; int array[][size], int size) {
+    return vlaSum2D(size, array);
+}
+*/

backend.native/tests/interop/basics/types.kt

@@ -9,4 +9,11 @@ fun main() {
     }
 
     assertEquals(1u, ForwardDeclaredEnum.ONE.value)
+
+    assertEquals(6, vlaSum(3, cValuesOf(1, 2, 3)))
+    assertEquals(10, vlaSum2D(2, cValuesOf(1, 2, 3, 4)))
+    assertEquals(21, vlaSum2DBothDimensions(2, 3, cValuesOf(1, 2, 3, 4, 5, 6)))
+
+    // Not supported by clang:
+    // assertEquals(10, vlaSum2DForward(cValuesOf(1, 2, 3, 4), 2))
 }