From 8521c10309ea1b3ef276a6eb666a19f27e9f72b5 Mon Sep 17 00:00:00 2001
From: Fabian Greffrath <fabian@greffrath.com>
Date: Mon, 4 Jul 2022 13:02:00 +0200
Subject: [PATCH] don't let failed loadgame attempts reset gameepisode/gamemap
 (#643)

---
 src/g_game.c | 26 ++++++++++++++++----------
 src/g_game.h |  1 -
 2 files changed, 16 insertions(+), 11 deletions(-)

diff --git a/src/g_game.c b/src/g_game.c
index 1b209b14..2c8cedcc 100644
--- a/src/g_game.c
+++ b/src/g_game.c
@@ -1683,16 +1683,16 @@ char* G_MBFSaveGameName(int slot)
 //
 // killough 12/98: use faster algorithm which has less IO
 
-ULong64 G_Signature(void)
+static ULong64 G_Signature(int sig_epi, int sig_map)
 {
   ULong64 s = 0;
   int lump, i;
   char name[9];
   
   if (gamemode == commercial)
-    sprintf(name, "map%02d", gamemap);
+    sprintf(name, "map%02d", sig_map);
   else
-    sprintf(name, "E%dM%d", gameepisode, gamemap);
+    sprintf(name, "E%dM%d", sig_epi, sig_map);
 
   lump = W_CheckNumForName(name);
 
@@ -1739,7 +1739,7 @@ static void G_DoSaveGame(void)
   *save_p++ = gamemap;
 
   {  // killough 3/16/98, 12/98: store lump name checksum
-    uint64_t checksum = G_Signature();
+    uint64_t checksum = G_Signature(gameepisode, gamemap);
     saveg_write64(checksum);
   }
 
@@ -1818,6 +1818,7 @@ static void G_DoLoadGame(void)
   int  length, i;
   char vcheck[VERSIONSIZE];
   byte saveg_complevel = 203;
+  int tmp_compat, tmp_skill, tmp_epi, tmp_map;
 
   // [crispy] loaded game must always be single player.
   // Needed for ability to use a further game loading, as well as
@@ -1860,16 +1861,15 @@ static void G_DoLoadGame(void)
   }
 
   // killough 2/14/98: load compatibility mode
-  compatibility = *save_p++;
+  tmp_compat = *save_p++;
 
-  gameskill = *save_p++;
-  gameepisode = *save_p++;
-  gamemap = *save_p++;
-  gamemapinfo = G_LookupMapinfo(gameepisode, gamemap);
+  tmp_skill = *save_p++;
+  tmp_epi = *save_p++;
+  tmp_map = *save_p++;
 
   if (!forced_loadgame)
    {  // killough 3/16/98, 12/98: check lump name checksum
-     uint64_t checksum = G_Signature();
+     uint64_t checksum = G_Signature(tmp_epi, tmp_map);
      uint64_t rchecksum = saveg_read64();
      if (checksum != rchecksum)
        {
@@ -1886,6 +1886,12 @@ static void G_DoLoadGame(void)
 
   while (*save_p++);
 
+  compatibility = tmp_compat;
+  gameskill = tmp_skill;
+  gameepisode = tmp_epi;
+  gamemap = tmp_map;
+  gamemapinfo = G_LookupMapinfo(gameepisode, gamemap);
+
   for (i=0 ; i<MAXPLAYERS ; i++)
     playeringame[i] = *save_p++;
   save_p += MIN_MAXPLAYERS-MAXPLAYERS;         // killough 2/28/98
diff --git a/src/g_game.h b/src/g_game.h
index 9aa25527..79458c63 100644
--- a/src/g_game.h
+++ b/src/g_game.h
@@ -67,7 +67,6 @@ byte *G_ReadOptionsMBF21(byte *demo_p);
 byte *G_WriteOptions(byte *demo_p);        // killough 3/1/98
 void G_PlayerReborn(int player);
 void G_DoVictory(void);
-ULong64 G_Signature(void);      // killough 12/98
 
 int G_ValidateMapName(const char *mapname, int *pEpi, int *pMap);