Re: Lua 5.0 and 5.1 together

[John Belmonte <john@...>]

I wrote:
> Diego Nehab wrote:
> 
>>Cool. I totally agree with your suggestion. I guess back then I was in
>>Brazil and too busy with the beach. :)
>>
>>As for not needing the support of the authors, this would force us to
>>patch the lua.c and/or loadlib.c. Since the 5.1.1 has not yet been
>>released...
>>
>>So, what is it going to be, people?
> 
> 
> Patching Lua to take care of distribution details is not a big deal, we
> already do it for other things (e.g. patching luaconf.h to add /usr/...
> variants to search paths).  Only one person need do the work and we can
> then share the patch.  I'll take a stab at it this weekend.

Attached is a backwards-compatible patch to check e.g. LUA_5_1_PATH
before LUA_PATH when looking up Lua environment variables (LUA_PATH,
LUA_CPATH, and LUA_INIT).  If the versioned variable exists then the
non-versioned one is not used at all.

--John

diff -urN lua-5.1.orig/src/loadlib.c lua-5.1/src/loadlib.c
--- lua-5.1.orig/src/loadlib.c	2005-12-29 10:32:11.000000000 -0500
+++ lua-5.1/src/loadlib.c	2006-04-09 16:24:16.000000000 -0400
@@ -586,13 +586,23 @@
 /* }====================================================== */
 
 
+static const char * getlenv(lua_State *L, const char* envname) {
+  /* try version-specific name first (e.g. LUA_5_1_PATH for LUA_PATH) */
+  const char *envname2 = luaL_gsub(L, envname, "LUA", "LUA_5_1");
+  const char *val = getenv(envname2);
+  if (val == NULL)
+    val = getenv(envname);
+  lua_remove(L, -1);
+  return val;
+}
+
 
 /* auxiliary mark (for internal use) */
 #define AUXMARK		"\1"
 
 static void setpath (lua_State *L, const char *fieldname, const char *envname,
                                    const char *def) {
-  const char *path = getenv(envname);
+  const char *path = getlenv(L, envname);
   if (path == NULL)  /* no environment variable? */
     lua_pushstring(L, def);  /* use default */
   else {
diff -urN lua-5.1.orig/src/lua.c lua-5.1/src/lua.c
--- lua-5.1.orig/src/lua.c	2005-12-29 11:23:32.000000000 -0500
+++ lua-5.1/src/lua.c	2006-04-09 16:24:22.000000000 -0400
@@ -305,8 +305,19 @@
 }
 
 
+static const char * getlenv(lua_State *L, const char* envname) {
+  /* try version-specific name first (e.g. LUA_5_1_PATH for LUA_PATH) */
+  const char *envname2 = luaL_gsub(L, envname, "LUA", "LUA_5_1");
+  const char *val = getenv(envname2);
+  if (val == NULL)
+    val = getenv(envname);
+  lua_remove(L, -1);
+  return val;
+}
+
+
 static int handle_luainit (lua_State *L) {
-  const char *init = getenv("LUA_INIT");
+  const char *init = getlenv(L, "LUA_INIT");
   if (init == NULL) return 0;  /* status OK */
   else if (init[0] == '@')
     return dofile(L, init+1);