From d57c8cc9f42a3b2ba56ef911cc8c2595921ec4d8 Mon Sep 17 00:00:00 2001
From: kichikuou <KichikuouChrome@gmail.com>
Date: Sat, 12 Jul 2025 15:18:52 +0900
Subject: [PATCH] Dungeons & Dolls: Call global variable destructors on exit

Early versions of System4 (Sys42VM.dll < 3.0) execute destructors for
global variables on exit.

Dungeons & Dolls saves its game state in the destructors of global
variables (~CDataDoll(), ~CDataItem(), ~CDataMain()), so the game was
not saved in xsystem4 before this.

This behavior has some quirks:
 * Destructors for variables on the call stack are not called on exit.
 * Destructors are called in the reverse order of the global variable
   declarations.
 * Inside a destructor, it is possible to access another global variable
   whose destructor has already been called (!).

Since this is a problematic behavior that was removed in later versions
of Sys42VM, let's add minimal support for it as a game-specific hack.
---
 include/xsystem4.h |  1 +
 src/hacks.c        |  3 +++
 src/vm.c           | 20 ++++++++++++++++++++
 3 files changed, 24 insertions(+)

diff --git a/include/xsystem4.h b/include/xsystem4.h
index 3bdf14f..f81f71f 100644
--- a/include/xsystem4.h
+++ b/include/xsystem4.h
@@ -91,5 +91,6 @@ extern bool game_rance02_mg;
 extern bool game_rance6_mg;
 extern bool game_rance7_mg;
 extern bool game_rance8;
+extern bool game_dungeons_and_dolls;
 
 #endif /* XSYSTEM4_H */
diff --git a/src/hacks.c b/src/hacks.c
index 69c6bff..ca541f0 100644
--- a/src/hacks.c
+++ b/src/hacks.c
@@ -37,6 +37,7 @@ bool game_rance02_mg = false;
 bool game_rance6_mg = false;
 bool game_rance7_mg = false;
 bool game_rance8 = false;
+bool game_dungeons_and_dolls = false;
 
 static void write_instruction0(struct buffer *out, enum opcode op)
 {
@@ -205,6 +206,8 @@ void apply_game_specific_hacks(struct ain *ain)
 		apply_rance7_hacks(ain);
 	} else if (!strcmp(game_name, "ランス・クエスト") || !strcmp(game_name, "Rance Quest")) {
 		game_rance8 = true;
+	} else if (!strcmp(game_name, "ＤＵＮＧＥＯＮＳ＆ＤＯＬＬＳ")) {
+		game_dungeons_and_dolls = true;
 	}
 	free(game_name);
 }
diff --git a/src/vm.c b/src/vm.c
index 51d0b99..4b4a6f8 100644
--- a/src/vm.c
+++ b/src/vm.c
@@ -2319,8 +2319,28 @@ static void vm_execute(void)
 	}
 }
 
+static void call_global_destructors(void)
+{
+	if (heap_size <= 0 || heap[0].ref <= 0)
+		return;
+	struct page *global_page = heap_get_page(0);
+	// Call global variable destructors, but do not unref them because the
+	// destructors may reference other global variables.
+	for (int i = global_page->nr_vars - 1; i >= 0; i--) {
+		if (variable_type(global_page, i, NULL, NULL) != AIN_STRUCT)
+			continue;
+		int slot = global_page->values[i].i;
+		delete_struct(heap_get_page(slot)->index, slot);
+	}
+}
+
 static void vm_free(void)
 {
+	if (game_dungeons_and_dolls) {
+		// Dungeons & Dolls saves the game state in destructors of global variables
+		call_global_destructors();
+	}
+
 	// call library exit routines
 	exit_libraries();
 	// flush call stack