Lua inside shared library conflict with Nginx or websocketpp?

Question

I'm using a red pitaya board (version 125-14) where user apps (compiled to .so file) are loaded dynamically in nginx upon web request. More specifically, Nginx starts a websocket server and the app is loaded to process websocket data. Recently I'd like to integrate lua inside my app, but a basic lua_pcall leads to segfault.

    lua_State* L = luaL_newstate();
    luaL_openlibs(L);
    // execute script
    const char lua_script[] = "a=1;";
    int load_stat = luaL_loadbuffer(L, lua_script, strlen(lua_script), lua_script);
    lua_pcall(L, 0, 0, 0);
    // cleanup
    lua_close(L);

So I added -g when compiling Lua and use gdb to see if there is more infomation. That's what I got with backtrace:

Thread 2 "nginx" received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0xb3796440 (LWP 27528)]
0xb382fb5a in luaD_precall (L=0xb2f771c0, func=0xfffffff0, nresults=0) at ldo.c:511
511       switch (ttypetag(s2v(func))) {
(gdb) backtrace
#0  0xb382fb5a in luaD_precall (L=0xb2f771c0, func=0xfffffff0, nresults=0) at ldo.c:511
#1  0xb382fdd2 in ccall (L=0xb2f771c0, func=0xfffffff0, nResults=0, inc=65537) at ldo.c:575
#2  0xb382fe36 in luaD_callnoyield (L=0xb2f771c0, func=0xfffffff0, nResults=0) at ldo.c:595
#3  0xb382cc5a in f_call (L=0xb2f771c0, ud=0xb3795304) at lapi.c:1031
#4  0xb382f17e in luaD_rawrunprotected (L=0xb2f771c0, f=0xb382cc3d <f_call>, ud=0xb3795304)
    at ldo.c:144
#5  0xb38303e4 in luaD_pcall (L=0xb2f771c0, func=0xb382cc3d <f_call>, u=0xb3795304,
    old_top=1292402216, ef=0) at ldo.c:892
#6  0xb382cce4 in lua_pcallk (L=0xb2f771c0, nargs=0, nresults=0, errfunc=0, ctx=0, k=0x0)
    at lapi.c:1057
#7  0xb3821870 in setupLUA ()
    at /root/.vs/CMakeProject1/657aa1fb-2594-4c6c-95fc-066d885f3252/src/CMakeProject1/CMakeProject1.cpp:103

It seems that the function pointer passing in is invalid (0xfffffff0). And it implies there is something wrong with the Lua stack?

Compiling the exact code as standalone executable is OK, no segfault and the result is correct.