Lua uses require to load the shared library successfully, but the return is Boolean (always true)

First look at require Help document for

If the loader returns any non-nil value, require assigns the returned value to package.loaded[modname]. If the loader does not return a non-nil value and has not assigned any value to package.loaded[modname], then require assigns true to this entry

The meaning of this sentence is ： If the loader returns a non null value , Then assign this non null value to package.loaded[modname] That is to say require The return value of . If the loader no return value , Then it will be assigned a true.

that , Why? loader There is no return value ？ Nothing but 2 Medium condition

xxx.so( or xxx.dll) The agreed interface of the shared library int luaopen_xxx function

1、 Not to lua The stack returns nothing , That is, there is no direction lua Export any function .

2、 Export content , But I didn't tell lua.luaopen_xxx Signature compliance lua_CFunction, The passage of this function

returns in C the number of results（ use C The number of results returned by the language ）.

That is to say luaopen_xxx The return value of must not be 0, Usually export function table ,return 1.