From 8bc8946be888f8b0e1c08369a39ecbc99f914a59 Mon Sep 17 00:00:00 2001 From: James R Date: Sat, 10 Oct 2020 16:43:09 -0700 Subject: [PATCH] Turn the lua sector lines hack into a macro --- src/doomtype.h | 8 ++++++++ src/lua_maplib.c | 2 +- 2 files changed, 9 insertions(+), 1 deletion(-) diff --git a/src/doomtype.h b/src/doomtype.h index 0aa3e23e0..4e13ba96d 100644 --- a/src/doomtype.h +++ b/src/doomtype.h @@ -371,4 +371,12 @@ typedef UINT32 tic_t; #define WSTRING2(s) L ## s #define WSTRING(s) WSTRING2 (s) +/* +A hack by Monster Iestyn: Return a pointer to a field of +a struct from a pointer to another field in the struct. +Needed for some lua shenanigans. +*/ +#define FIELDFROM( type, field, have, want ) \ + (void *)((intptr_t)(field) - offsetof (type, have) + offsetof (type, want)) + #endif //__DOOMTYPE__ diff --git a/src/lua_maplib.c b/src/lua_maplib.c index 12a0be27d..132c81e48 100644 --- a/src/lua_maplib.c +++ b/src/lua_maplib.c @@ -447,7 +447,7 @@ static int sectorlines_get(lua_State *L) // get the "linecount" by shifting our retrieved memory address of "lines" to where "linecount" is in the sector_t, then dereferencing the result // we need this to determine the array's actual size, and therefore also the maximum value allowed as an index // this only works if seclines is actually a pointer to a sector's lines member in memory, oh boy - numoflines = (size_t)(*(size_t *)(((size_t)seclines) - (offsetof(sector_t, lines) - offsetof(sector_t, linecount)))); + numoflines = *(size_t *)FIELDFROM (sector_t, seclines, lines,/* -> */linecount); /* OLD HACK // check first linedef to figure which of its sectors owns this sector->lines pointer