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- Subject: What is the name of the calling function?
- From: Dirk Laurie <dirk.laurie@...>
- Date: Tue, 7 May 2013 09:02:48 +0200
You have seen them all too often.
stdin:1: bad argument #1 to 'sqrt' (number expected, got string)
stdin:1: bad argument #1 to 'getlocal' (level out of range)
They can be issued from the C API by these:
void luaL_checktype (lua_State *L, int arg, int t);
void luaL_argcheck (lua_State *L, int cond, int arg, const char *extramsg);
int luaL_argerror (lua_State *L, int arg, const char *extramsg);
You can fake them from inside Lua, easy enough. For example, I have:
argcheck = function(cond,pos,fct,msg)
if not cond then
error(("bad argument "..pos.." to '%s' (%s)"):format(fct,msg))
Notice the difference? The C API knows the name of the calling
function, the Lua function has to be told what it is.
How hard is it for a running function to find out the name of the
function from which it was called?
Look at this.
function fct(x,y) return x+y end
adder = fct
fct = nil
You get a standard error message that says:
stdin:1: attempt to perform arithmetic on local 'y' (a string value)
stdin:1: in function 'adder'
stdin:1: in main chunk
[C]: in ?
I want that name "adder" in my own customized message (not
always an error message) that can be issued from inside the
body of "fct". I don't wnat the name `fct` that appears in
`function fct(x,y)`, the one I can easily pass to my `argcheck`.
I've snooped around with debug.getlocal and debug.getinfo and
I can't find it.