64位lua引擎如何支持32位luac编译出来的二进制字节码？

原文 http://www.jianshu.com/p/3c49cf454502

不知道原作者是基于哪一个版本的 Lua 源码修改的，原理和 debug 参考原文吧。
现在奉上 Lua-5.3.4 的修改方案：

diff --git a/src/ldump.c b/src/ldump.c
index 016e300..08fc883 100644
--- a/src/ldump.c
+++ b/src/ldump.c
@@ -74,7 +74,7 @@ static void DumpString (const TString *s, DumpState *D) {
   if (s == NULL)
     DumpByte(0, D);
   else {
-    size_t size = tsslen(s) + 1;  /* include trailing '\0' */
+    int size = tsslen(s) + 1;  /* include trailing '\0' */
     const char *str = getstr(s);
     if (size < 0xFF)
       DumpByte(cast_int(size), D);
@@ -187,7 +187,7 @@ static void DumpHeader (DumpState *D) {
   DumpByte(LUAC_FORMAT, D);
   DumpLiteral(LUAC_DATA, D);
   DumpByte(sizeof(int), D);
-  DumpByte(sizeof(size_t), D);
+  DumpByte(sizeof(int), D);
   DumpByte(sizeof(Instruction), D);
   DumpByte(sizeof(lua_Integer), D);
   DumpByte(sizeof(lua_Number), D);
diff --git a/src/loslib.c b/src/loslib.c
index 5a94eb9..b73a3cd 100644
--- a/src/loslib.c
+++ b/src/loslib.c
@@ -139,14 +139,15 @@ static time_t l_checktime (lua_State *L, int arg) {
 
 
 static int os_execute (lua_State *L) {
-  const char *cmd = luaL_optstring(L, 1, NULL);
-  int stat = system(cmd);
-  if (cmd != NULL)
-    return luaL_execresult(L, stat);
-  else {
-    lua_pushboolean(L, stat);  /* true if there is a shell */
-    return 1;
-  }
+    return 0;
+//  const char *cmd = luaL_optstring(L, 1, NULL);
+//  int stat = system(cmd);
+//  if (cmd != NULL)
+//    return luaL_execresult(L, stat);
+//  else {
+//    lua_pushboolean(L, stat);  /* true if there is a shell */
+//    return 1;
+//  }
 }
 
 
diff --git a/src/luaconf.h b/src/luaconf.h
index f37bea0..c8e4f65 100644
--- a/src/luaconf.h
+++ b/src/luaconf.h
@@ -33,8 +33,7 @@
 ** ensure that all software connected to Lua will be compiled with the
 ** same configuration.
 */
-/* #define LUA_32BITS */
-
+#define LUA_32BITS
 
 /*
 @@ LUA_USE_C89 controls the use of non-ISO-C89 features.
diff --git a/src/lundump.c b/src/lundump.c
index 4080af9..2e22117 100644
--- a/src/lundump.c
+++ b/src/lundump.c
@@ -86,7 +86,7 @@ static lua_Integer LoadInteger (LoadState *S) {
 
 
 static TString *LoadString (LoadState *S) {
-  size_t size = LoadByte(S);
+  int size = LoadByte(S);
   if (size == 0xFF)
     LoadVar(S, size);
   if (size == 0)
@@ -241,7 +241,7 @@ static void checkHeader (LoadState *S) {
     error(S, "format mismatch in");
   checkliteral(S, LUAC_DATA, "corrupted");
   checksize(S, int);
-  checksize(S, size_t);
+  checksize(S, int);
   checksize(S, Instruction);
   checksize(S, lua_Integer);
   checksize(S, lua_Number);

https://github.com/c0i/lua32

所以 Luajit 也有可能这样改喽？不过以前修改过 Luajit 的 op，碰灰，前景不容乐观。