Dear Devs, Sorry if this is not the best place for reporting bugs. I'm trying to use the lpeglabel library written in C and delivered as lpeglabel.so. $ ls testlabel.lua lpeglabel.so $ cat testlabel.lua require("lpeglabel") The ConTeXt binary cannot load the library because it lacks certain Lua API: $ context --forcecld --permitloadlib testlabel.lua ... fatal lua error: registered function call [1542]: ...tx/tex/texmf-context/tex/context/base/mkiv/l-package.lua:348: error loading module 'lpeglabel' from file './lpeglabel.so': ./lpeglabel.so: undefined symbol: lua_gettop ... nor does LuaTeX: $ luatex -luaonly testlabel.lua error loading module 'lpeglabel' from file './lpeglabel.so': ./lpeglabel.so: undefined symbol: lua_getiuservalue It seems that lua_gettop and others are optimized out from the `context` binary, while lua_getiuservalue and others are missing from `luatex`. I'm not sure if it works but I would suggest adding `__attribute__ ((used))` to the `LUA_API` macro if the binaries are compiled with gcc. Best, Sylvain