From c88ff19190dd17971004a35e755560ee0877d14f Mon Sep 17 00:00:00 2001
From: MysterD <myster@d>
Date: Tue, 1 Sep 2020 22:06:36 -0700
Subject: [PATCH] Prevent infinite looping of Mario action transitions

There have been several times where the unpredictable behavior of
a remote player where execute_mario_action() would get caught in
an infinite loop. Now we attempt to detect an infinite hang and
escape from it. The sequence of actions will be recorded into an
errorlog.txt file. In debug mode this infinite hang will cause an
assertion to fail, crashing the game. In normal mode the game will
break out of it and hopefully carry on normally after new packets
come in.

I believe this addresses github issue #12 but I can't be sure.
---
 Makefile         |  6 ++++++
 src/game/mario.c | 54 +++++++++++++++++++++++++++++++++++++++++++++++-
 src/pc/logfile.c | 40 +++++++++++++++++++++++++++++++++++
 src/pc/logfile.h |  7 +++++++
 4 files changed, 106 insertions(+), 1 deletion(-)
 create mode 100644 src/pc/logfile.c
 create mode 100644 src/pc/logfile.h

diff --git a/Makefile b/Makefile
index c0356728..378f10a9 100644
--- a/Makefile
+++ b/Makefile
@@ -555,6 +555,12 @@ endif
 
 # Check for enhancement options
 
+# Check for debug option
+ifeq ($(DEBUG),1)
+  CC_CHECK += -DDEBUG
+  CFLAGS += -DDEBUG
+endif
+
 # Check for immediate load option
 ifeq ($(IMMEDIATELOAD),1)
   CC_CHECK += -DIMMEDIATELOAD
diff --git a/src/game/mario.c b/src/game/mario.c
index 3466825a..510a05f6 100644
--- a/src/game/mario.c
+++ b/src/game/mario.c
@@ -1,5 +1,9 @@
 #include <PR/ultratypes.h>
 
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+
 #include "sm64.h"
 #include "area.h"
 #include "audio/data.h"
@@ -40,6 +44,8 @@
 #include "bettercamera.h"
 #endif
 
+#define MAX_HANG_PREVENTION 64
+
 u16 gFreezeMario = 0;
 
 u32 unused80339F10;
@@ -1760,6 +1766,44 @@ void func_sh_8025574C(void) {
     }
 }
 
+static u8 prevent_hang(u32 hangPreventionActions[], u8* hangPreventionIndex) {
+    // save the action sequence
+    hangPreventionActions[*hangPreventionIndex] = gMarioState->action;
+    *hangPreventionIndex = *hangPreventionIndex + 1;
+    if (*hangPreventionIndex < MAX_HANG_PREVENTION) { return FALSE; }
+
+    // only dump the log once
+    static u8 dumped = FALSE;
+    if (dumped) { return TRUE; }
+    dumped = TRUE;
+
+    // open the log
+    FILE* f = NULL;
+    if (!logfile_open(&f)) { return TRUE; }
+
+    // complain to console
+    printf("#######################################\n");
+    printf("# HANG PREVENTED                      #\n");
+    printf("# Send the error log to the developer #\n");
+    printf("#######################################\n");
+
+    // save to log
+    fprintf(f, "(gMarioState->action: hang prevention begin)\n");
+    for (int i = 0; i < MAX_HANG_PREVENTION; i++) {
+        fprintf(f, "%08X\n", hangPreventionActions[i]);
+    }
+    fprintf(f, "(gMarioState->action: hang prevention end)\n");
+
+    logfile_close();
+
+    // force the crash in debug mode
+#ifdef DEBUG
+    assert(hangPreventionIndex == 0);
+#endif
+
+    return TRUE;
+}
+
 /**
  * Main function for executing Mario's behavior.
  */
@@ -1768,7 +1812,6 @@ s32 execute_mario_action(UNUSED struct Object *o) {
     /**
     * Cheat stuff
     */
-
     if (Cheats.EnableCheats)
     {
         if (Cheats.GodMode)
@@ -1802,6 +1845,9 @@ s32 execute_mario_action(UNUSED struct Object *o) {
             if (gFreezeMario < 1 && gDialogID != -1) { gFreezeMario = 1; }
         }
 
+        u32 hangPreventionActions[MAX_HANG_PREVENTION];
+        u8 hangPreventionIndex = 0;
+
         // The function can loop through many action shifts in one frame,
         // which can lead to unexpected sub-frame behavior. Could potentially hang
         // if a loop of actions were found, but there has not been a situation found.
@@ -1810,6 +1856,12 @@ s32 execute_mario_action(UNUSED struct Object *o) {
             if (gMarioState->playerIndex == 0 && gFreezeMario > 0 && (gMarioState->action & ACT_GROUP_MASK) != ACT_GROUP_CUTSCENE) {
                 break;
             }
+
+            // this block can get stuck in an infinite loop due to unexpected circumstances arising from networked players
+            if (prevent_hang(hangPreventionActions, &hangPreventionIndex)) {
+                break;
+            }
+
             switch (gMarioState->action & ACT_GROUP_MASK) {
                 case ACT_GROUP_STATIONARY:
                     inLoop = mario_execute_stationary_action(gMarioState);
diff --git a/src/pc/logfile.c b/src/pc/logfile.c
new file mode 100644
index 00000000..d49b985e
--- /dev/null
+++ b/src/pc/logfile.c
@@ -0,0 +1,40 @@
+// logfile.c - handles opening and closing of the log file
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <stdbool.h>
+
+#define LOGFILE_NAME "errorlog.txt"
+
+static bool firstOpen = true;
+static bool active = false;
+static FILE* logfile = NULL;
+
+bool logfile_open(FILE** f) {
+    if (active) {
+        *f = logfile;
+        return true;
+    }
+
+    printf("Initiating logfile to '%s'\n", LOGFILE_NAME);
+
+    logfile = fopen(fs_get_write_path(LOGFILE_NAME), "a");
+    if (logfile == NULL) { return false; }
+    *f = logfile;
+
+    if (firstOpen) {
+        fprintf(logfile, "--- new run ---\n");
+        firstOpen = false;
+    }
+
+    active = true;
+    return logfile;
+}
+
+void logfile_close(void) {
+    if (!active) { return; }
+    fflush(logfile);
+    fclose(logfile);
+    active = false;
+}
\ No newline at end of file
diff --git a/src/pc/logfile.h b/src/pc/logfile.h
new file mode 100644
index 00000000..89cee3d2
--- /dev/null
+++ b/src/pc/logfile.h
@@ -0,0 +1,7 @@
+#ifndef LOGFILE_H
+#define LOGFILE_H
+
+bool logfile_open(FILE** f);
+void logfile_close(void);
+
+#endif