Re: base_open fails to set _G

[Alexander Gladysh <agladysh@...>]

On Fri, Feb 17, 2012 at 07:15, Alexander Gladysh <agladysh@gmail.com> wrote:
> Hi, list!
>
> (This question contains some hardcore Adobe-specific details. If that
> distracts you, please view it from the "unknown alpha-quality platform
> with C compiler" point of view.)
>
> I'm debugging a weird bug in the Lua Alchemy that appears with a
> certain build configuration (with the same Alchemy SWC the bug appears
> if AIR app built with FDT, and does not appear if built with raw AIR
> SDK from command-line). In this case the Lua 5.1.4 code is built with
> llvm-based Adobe Alchemy, to Flash bytecode, and that bytecode is then
> translated to ARM code for iOS devices via latest AIR, all done by
> Adobe pipeline, some of which is no longer supported alpha, so things
> do get pretty weird.
>
> I found that base_open() fails to set _G (i.e. lua_getglobal(L, "_G")
> returns nil). See the code and the output below.
>
> I'm a bit baffled. Maybe someone would have some idea on what else to
> check from the C code side? Meanwhile I will continue to attack the
> problem from "what is different between the FDT and SDK builds" side.
>
> I assume that, at least, Alchemy compiler did not went nuts, since the
> same SWC works in other configuration, but something in pipeline later
> (like bytecode to ARM translator) maybe could... Or maybe I just doing
> something somewhere that leads to undefined behaviour in C.
>
> Thank you,
> Alexander.
>
> //
> // This is what I changed in 5.1.4 code to debug what's happening:
> //
> static void base_open (lua_State *L) {
>  /* set global _G */
>
>  char buf[4096];
>
>  sztrace("0057.1.0010 -- base_open BEGIN");
>
>  lua_pushvalue(L, LUA_GLOBALSINDEX);
>
>  sztrace("0057.1.0020");
>
>  sprintf(buf, "0057.1.0021 L %p top type %s", L, luaL_typename(L, -1));
>  sztrace(buf);
>
>  sztrace("0057.1.0022");
>
>  lua_setglobal(L, "_G");
>
>  sztrace("0057.1.0023");
>
>  lua_getglobal(L, "_G");
>
>  sztrace("0057.1.0024");
>
>  sprintf(buf, "0057.1.0025 L %p top type %s", L, luaL_typename(L, -1));
>  sztrace(buf);
>
>  sztrace("0057.1.0026");
>
>  lua_pop(L, 1);
>
>  sztrace("0057.1.0030");
>
>  /* open lib into global table */
>  luaL_register(L, "_G", base_funcs);
> .... And at this point I see a segfault

A small update: actual crash happens (inside luaL_register() call) in
luaL_findtable() at this line

https://github.com/lua-alchemy/lua-alchemy/blob/master/alchemy/lib/lua51/src/lauxlib.c#L371

(Wish I had a proper debugger for that stuff... :-( )

> My initialization function:
> https://github.com/lua-alchemy/lua-alchemy/blob/ag/150/weird-bugs/alchemy/wrapper/lua_wrapper.gg#L32
>
> The output:
>
> 0057.1.0010 -- base_open BEGIN
> 0057.1.0020
> 0057.1.0021 L 0x10e000 top type table
> 0057.1.0022
> 0057.1.0023
> 0057.1.0024
> 0057.1.0025 L 0x10e000 top type nil
> 0057.1.0026
> 0057.1.0030
> RangeError: Error #1506: The specified range is invalid.
>        at cmodule.lua_wrapper::FSM_newkey/work()
>        at Function/<anonymous>()
>        at Function/<anonymous>()
>        at luaAlchemy::lua_wrapper$/luaInitializeState()[/Users/agladysh/projects/lua-alchemy/alchemy/wrapper/bin/src/luaAlchemy/lua_wrapper.as:7]
>        at LuaAlchemyiOSTest/onCreationComplete()[/Users/agladysh/Documents/Adobe
> Flash Builder 4.6/LuaAlchemyiOSTest/src/LuaAlchemyiOSTest.mxml:14]
>        at LuaAlchemyiOSTest/___LuaAlchemyiOSTest_Application1_creationComplete()[/Users/agladysh/Documents/Adobe
> Flash Builder 4.6/LuaAlchemyiOSTest/src/LuaAlchemyiOSTest.mxml:4]
>        at flash.events::EventDispatcher/dispatchEventFunction()
>        at flash.events::EventDispatcher/dispatchEvent()
>        at mx.core::UIComponent/dispatchEvent()[E:\dev\4.y\frameworks\projects\framework\src\mx\core\UIComponent.as:13152]
>        at mx.core::UIComponent/set
> initialized()[E:\dev\4.y\frameworks\projects\framework\src\mx\core\UIComponent.as:1818]
>        at mx.managers::LayoutManager/doPhasedInstantiation()[E:\dev\4.y\frameworks\projects\framework\src\mx\managers\LayoutManager.as:842]
>        at mx.managers::LayoutManager/doPhasedInstantiationCallback()[E:\dev\4.y\frameworks\projects\framework\src\mx\managers\LayoutManager.as:1180]