diff -up texlive-core-20170520/source/texk/web2c/luatexdir/luaffi/ctype.c.crashfix texlive-core-20170520/source/texk/web2c/luatexdir/luaffi/ctype.c

--- texlive-core-20170520/source/texk/web2c/luatexdir/luaffi/ctype.c.crashfix	2017-09-12 14:16:33.675640506 -0400

+++ texlive-core-20170520/source/texk/web2c/luatexdir/luaffi/ctype.c	2017-09-12 14:16:53.953166205 -0400

@@ -245,6 +245,10 @@ void* to_cdata(lua_State* L, int idx, st

     lua_pop(L, 1); /* mt */

     cd = (struct cdata*) lua_touserdata(L, idx);

+    if (!cd) {

+        lua_pushnil(L);

+        return NULL;

+    }

     *ct = cd->type;

     lua_getuservalue(L, idx);

diff -up texlive-core-20170520/source/texk/web2c/luatexdir/luaffi/ffi.h.crashfix texlive-core-20170520/source/texk/web2c/luatexdir/luaffi/ffi.h

--- texlive-core-20170520/source/texk/web2c/luatexdir/luaffi/ffi.h.crashfix	2017-09-12 14:17:26.290409821 -0400

+++ texlive-core-20170520/source/texk/web2c/luatexdir/luaffi/ffi.h	2017-09-12 14:17:43.041018016 -0400

@@ -370,7 +370,7 @@ __declspec(align(16))

 #endif

 struct cdata {

     const struct ctype type

-#ifdef __GNUC__

+#if 0 /* def __GNUC__ */

       __attribute__ ((aligned(16)))

 #endif

       ;