[luatex] Profiling LuaTeX / difference with jit

[Patrick Gundlach]

Hi all,

I try to understand Lua's debug library and came across differences between 
luatex and luajittex.

See the following program:

------------
function a(cp)
    return string.format("abc %d",cp)
end


function dothings()
        a(2)
        a(2)
end


function onDebugHook( hookType )
        local funcInfo = debug.getinfo( 2 )
        if hookType == "call" then
                print("call",funcInfo.name or "?")
        elseif hookType == "return" then
                print("return",funcInfo.name or "?")
        end
end

debug.sethook( onDebugHook, 'cr')


dothings()
--------------

with "luatex --luaonly main.lua" I get a balanced call/return list:

--------------
return  sethook
call    dothings
call    a
call    format
return  format
return  a
call    a
call    format
return  format
return  a
return  dothings
return  ?
--------------


with "luajittex --luaonly main.lua" I get

--------------
call    dothings
call    a
call    a
call    a
call    a
return  dothings
return  ?
--------------


I guess this has to do with optimizations that Luajittex does. 

Just out of curiosity (I can of course work with regular LuaTeX) Now let's say 
I want to have the output from LuaTeX with the LuajitTeX program, (how) is this 
possible?

Patrick