macro name a,b,c
{
if a eq true
a#.param = 1
end if

if ~ defined a#.param ;??????
.....
end
}

if call marco with "name,aaa,sf,asdf" to be get error,
==========>
a#.param
error: undefined symbol.

This is the code I used
But I couldn't reproduce the error. And if I use "name true, sf, asd" no error neither and "hello" is not displayed.

Can you provide more info about what are you trying to do and if the "undefined symbol" error is really triggered by this macro? Providing a minimal code that produces this error would be the best.

You don't need that comma after macro name. Just write it as LocoDelAssembly proposed: name aaa,sf,asd. When you write this comma, it means that you pass nothing as first argument to your macro, thus making "aaa" second arg, "sf" third and "asdf" fourth. This makes "if a eq true" never succeed.

mike, but the error for writing that extra comma is not "undefined symbol" but "invalid macro arguments", so the error seems to be located somewhere else but luckystar provided too few code to trigger the error he says.