use Boom's P_UnsetThingPosition()/P_SetThingPosition() for Boom and earlier

[fabiangreffrath]

No description provided.

[fabiangreffrath]

This fixes the alienstcE2M5.lmp desync. I am still not sure what the underlying issue is, but it seems that the MBF code changes the order of mobj_t * elements in the blocklinks[] arrays.

[fabiangreffrath]

I only set the function pointers at the start of each map, so the COMP cheat continues to work.

[elf-alchemist]

Has this change thoroughly demo-tested? (Or will it later?) Obviously it should be made in order to match up with vanilla, certainly, but of course there's the possibility that newer vanilla/boom demos that may get screwed by this -- I guess my question is "how many of the newer demos will be desynced?"

This is also a similar consideration with the "planes differ" issue from DSDA (kraflab/dsda-doom#704) where in a implementation detail was quietly changed that caused backwards compat issues.

[Pedro-Beirao]

Has this change thoroughly demo-tested?

This has been tested against all dsdarchive demos with dsda-doom. It fixes the demos that desync, and makes the game hang against a few other demos.

This is expected, in vanilla those demos also hang.

But having the game hang isnt a good thing, so I think the plan is to catch the expection with I_Error()
Atleast thats why I havent merged it for dsda-doom yet

[fabiangreffrath]

But having the game hang isnt a good thing, so I think the plan is to catch the expection with I_Error() Atleast thats why I havent merged it for dsda-doom yet

--- a/src/p_maputl.c
+++ b/src/p_maputl.c
@@ -26,6 +26,7 @@
 #include "doomdata.h"
 #include "doomstat.h"
 #include "i_printf.h"
+#include "i_system.h"
 #include "m_bbox.h"
 #include "p_map.h"
 #include "p_maputl.h"
@@ -546,14 +547,18 @@ boolean blockmapfix;
 boolean P_BlockThingsIterator(int x, int y, boolean func(mobj_t*),
                               boolean do_blockmapfix)
 {
-  mobj_t *mobj;
+  mobj_t *mobj, *first;
 
   if (x < 0 || y < 0 || x >= bmapwidth || y >= bmapheight)
     return true;
 
-  for (mobj = blocklinks[y*bmapwidth+x]; mobj; mobj = mobj->bnext)
+  for (mobj = blocklinks[y*bmapwidth+x], first = mobj; mobj; mobj = mobj->bnext)
+  {
     if (!func(mobj))
       return false;
+    if (mobj->bnext == first)
+      I_Error("infitnite loop detected!");
+  }
 
   // Blockmap bug fix by Terry Hearst
   // https://github.com/fabiangreffrath/crispy-doom/pull/723