Re: suggesting change: lua_pcall error handlers to return multiple values

[Asko Kauppi <askok@...>]

Just to mention, I was able to bypass this limitation in Lane (2.0.3)  
by placing the stack trace via registry from error handler to the  
lua_pcall caller.

Lanes 2.0.3 will be able to provide this API to users:

	[...]|[ nil, err, stack_tbl ]= lane_h:join( [timeout_secs] )

	stack_tbl is an array of "<filename>:<line>" strings, describing  
where the error was thrown. Use table.concat() to format it to your  
liking (or just ignore it).

The stack_tbl is the new thing. Seems one was not able to get a stack  
trace of what had happened within a lane, if it errorred. Now, one can.

-asko


Asko Kauppi kirjoitti 22.1.2009 kello 21:30:

> In regards to the discussion concerning non-string error values,  
> there is a certain detail of Lua that in my opinion would deserve a  
> change.
>
> The 'lua_pcall' function allows an error handler, which can grab the  
> error message and modify it accordingly (normally, to add stack  
> trace). This implies that the error "message" (as it is called in  
> documentation) is a string. Non-string errors cannot be modified to  
> have a stack trace.
>
> Why not allow an error handler return multiple values?  What I have  
> in mind is two (error value + stack trace string). Currently,  
> 'lua_pcall' silently eats up any additional return values from the  
> error handler.
>
> -asko