refactor: replace wrenReturn___() with wrenSetSlot___() for writing values to arbitrary slots

The old wrenReturn___() functions only wrote to slot 0 for return values. The new wrenSetSlot___() functions allow writing to any slot index, making them general-purpose for manipulating the foreign call stack. This change updates all call sites, removes the dedicated returns test suite in favor of slots tests, and adjusts the VM internals to treat slot 0 as the return position rather than using a separate return mechanism.

test/api/benchmark.c

@@ -11,7 +11,7 @@ static void arguments(WrenVM* vm)
   result += wrenGetSlotDouble(vm, 3);
   result += wrenGetSlotDouble(vm, 4);
 
-  wrenReturnDouble(vm, result);
+  wrenSetSlotDouble(vm, 0, result);
 }
 
 WrenForeignMethodFn benchmarkBindMethod(const char* signature)

test/api/foreign_class.c

@@ -7,7 +7,7 @@ static int finalized = 0;
 
 static void apiFinalized(WrenVM* vm)
 {
-  wrenReturnDouble(vm, finalized);
+  wrenSetSlotDouble(vm, 0, finalized);
 }
 
 static void counterAllocate(WrenVM* vm)
@@ -27,7 +27,7 @@ static void counterIncrement(WrenVM* vm)
 static void counterValue(WrenVM* vm)
 {
   double value = *(double*)wrenGetSlotForeign(vm, 0);
-  wrenReturnDouble(vm, value);
+  wrenSetSlotDouble(vm, 0, value);
 }
 
 static void pointAllocate(WrenVM* vm)
@@ -64,7 +64,7 @@ static void pointToString(WrenVM* vm)
   char result[100];
   sprintf(result, "(%g, %g, %g)",
       coordinates[0], coordinates[1], coordinates[2]);
-  wrenReturnString(vm, result, (int)strlen(result));
+  wrenSetSlotString(vm, 0, result);
 }
 
 static void resourceAllocate(WrenVM* vm)

test/api/main.c

@@ -7,7 +7,7 @@
 #include "benchmark.h"
 #include "call.h"
 #include "foreign_class.h"
-#include "returns.h"
+#include "slots.h"
 #include "value.h"
 
 // The name of the currently executing API test.
@@ -36,7 +36,7 @@ static WrenForeignMethodFn bindForeignMethod(
   method = foreignClassBindMethod(fullName);
   if (method != NULL) return method;
   
-  method = returnsBindMethod(fullName);
+  method = slotsBindMethod(fullName);
   if (method != NULL) return method;
   
   method = valueBindMethod(fullName);

test/api/returns.c

@@ -1,51 +0,0 @@
-#include <string.h>
-
-#include "returns.h"
-
-static void implicitNull(WrenVM* vm)
-{
-  // Do nothing.
-}
-
-static void returnInt(WrenVM* vm)
-{
-  wrenReturnDouble(vm, 123456);
-}
-
-static void returnFloat(WrenVM* vm)
-{
-  wrenReturnDouble(vm, 123.456);
-}
-
-static void returnTrue(WrenVM* vm)
-{
-  wrenReturnBool(vm, true);
-}
-
-static void returnFalse(WrenVM* vm)
-{
-  wrenReturnBool(vm, false);
-}
-
-static void returnString(WrenVM* vm)
-{
-  wrenReturnString(vm, "a string", -1);
-}
-
-static void returnBytes(WrenVM* vm)
-{
-  wrenReturnString(vm, "a\0b\0c", 5);
-}
-
-WrenForeignMethodFn returnsBindMethod(const char* signature)
-{
-  if (strcmp(signature, "static Returns.implicitNull") == 0) return implicitNull;
-  if (strcmp(signature, "static Returns.returnInt") == 0) return returnInt;
-  if (strcmp(signature, "static Returns.returnFloat") == 0) return returnFloat;
-  if (strcmp(signature, "static Returns.returnTrue") == 0) return returnTrue;
-  if (strcmp(signature, "static Returns.returnFalse") == 0) return returnFalse;
-  if (strcmp(signature, "static Returns.returnString") == 0) return returnString;
-  if (strcmp(signature, "static Returns.returnBytes") == 0) return returnBytes;
-
-  return NULL;
-}

test/api/returns.h

@@ -1,3 +0,0 @@
-#include "wren.h"
-
-WrenForeignMethodFn returnsBindMethod(const char* signature);

test/api/returns.wren

@@ -1,23 +0,0 @@
-class Returns {
-  foreign static implicitNull
-
-  foreign static returnInt
-  foreign static returnFloat
-
-  foreign static returnTrue
-  foreign static returnFalse
-
-  foreign static returnString
-  foreign static returnBytes
-}
-
-System.print(Returns.implicitNull == null) // expect: true
-
-System.print(Returns.returnInt)  // expect: 123456
-System.print(Returns.returnFloat) // expect: 123.456
-
-System.print(Returns.returnTrue)  // expect: true
-System.print(Returns.returnFalse) // expect: false
-
-System.print(Returns.returnString) // expect: a string
-System.print(Returns.returnBytes.bytes.toList) // expect: [97, 0, 98, 0, 99]

test/api/slots.c

@@ -0,0 +1,83 @@
+#include <string.h>
+
+#include "slots.h"
+
+static void noSet(WrenVM* vm)
+{
+  // Do nothing.
+}
+
+static void getSlots(WrenVM* vm)
+{
+  bool result = true;
+  if (wrenGetSlotBool(vm, 1) != true) result = false;
+  // TODO: Test wrenGetSlotForeign().
+  
+  int length;
+  const char* bytes = wrenGetSlotBytes(vm, 2, &length);
+  if (length != 5) result = false;
+  if (memcmp(bytes, "by\0te", length) != 0) result = false;
+
+  if (wrenGetSlotDouble(vm, 3) != 12.34) result = false;
+  if (strcmp(wrenGetSlotString(vm, 4), "str") != 0) result = false;
+  
+  WrenValue* value = wrenGetSlotValue(vm, 5);
+
+  if (result)
+  {
+    // Otherwise, return the value so we can tell if we captured it correctly.
+    wrenSetSlotValue(vm, 0, value);
+    wrenReleaseValue(vm, value);
+  }
+  else
+  {
+    // If anything failed, return false.
+    wrenSetSlotBool(vm, 0, false);
+  }
+}
+
+static void setSlots(WrenVM* vm)
+{
+  WrenValue* value = wrenGetSlotValue(vm, 1);
+  
+  wrenSetSlotBool(vm, 1, true);
+  wrenSetSlotBytes(vm, 2, "by\0te", 5);
+  wrenSetSlotDouble(vm, 3, 12.34);
+  wrenSetSlotString(vm, 4, "str");
+  
+  // TODO: wrenSetSlotNull().
+  
+  // Read the slots back to make sure they were set correctly.
+  
+  bool result = true;
+  if (wrenGetSlotBool(vm, 1) != true) result = false;
+  
+  int length;
+  const char* bytes = wrenGetSlotBytes(vm, 2, &length);
+  if (length != 5) result = false;
+  if (memcmp(bytes, "by\0te", length) != 0) result = false;
+  
+  if (wrenGetSlotDouble(vm, 3) != 12.34) result = false;
+  if (strcmp(wrenGetSlotString(vm, 4), "str") != 0) result = false;
+
+  if (result)
+  {
+    // Move the value into the return position.
+    wrenSetSlotValue(vm, 0, value);
+    wrenReleaseValue(vm, value);
+  }
+  else
+  {
+    // If anything failed, return false.
+    wrenSetSlotBool(vm, 0, false);
+  }
+}
+
+WrenForeignMethodFn slotsBindMethod(const char* signature)
+{
+  if (strcmp(signature, "static Slots.noSet") == 0) return noSet;
+  if (strcmp(signature, "static Slots.getSlots(_,_,_,_,_)") == 0) return getSlots;
+  if (strcmp(signature, "static Slots.setSlots(_,_,_,_)") == 0) return setSlots;
+
+  return NULL;
+}

test/api/slots.h

@@ -0,0 +1,3 @@
+#include "wren.h"
+
+WrenForeignMethodFn slotsBindMethod(const char* signature);

test/api/slots.wren

@@ -0,0 +1,16 @@
+class Slots {
+  foreign static noSet
+
+  foreign static getSlots(bool, num, string, bytes, value)
+
+  foreign static setSlots(a, b, c, d)
+}
+
+// If nothing is set in the return slot, it retains its previous value, the
+// receiver.
+System.print(Slots.noSet == Slots) // expect: true
+
+var value = ["value"]
+System.print(Slots.getSlots(true, "by\0te", 12.34, "str", value) == value) // expect: true
+
+System.print(Slots.setSlots(value, 0, 0, 0) == value) // expect: true

test/api/value.c

@@ -11,7 +11,7 @@ static void setValue(WrenVM* vm)
 
 static void getValue(WrenVM* vm)
 {
-  wrenReturnValue(vm, value);
+  wrenSetSlotValue(vm, 0, value);
   wrenReleaseValue(vm, value);
 }