Re: Ravi bug related to setting of L->top in OP_RETURN

[Dibyendu Majumdar <mobile@...>]

On 8 August 2015 at 12:00, Dibyendu Majumdar <mobile@majumdar.org.uk> wrote:
> On 6 August 2015 at 22:55, Roberto Ierusalimschy <roberto@inf.puc-rio.br> wrote:
>> It is not only L->top that has a dual purpose; the stack has a dual
>> usage, due to the way that Lua uses a register-based VM. While inside
>> a Lua function, Lua preallocates in the stack all "registers" that the
>> function will eventually need. So, while running VM instructions in
>> one function, L->top points to the end of its activation record (stack
>> frame). When Lua enters or re-enters a Lua function, L->top must be
>> corrected to this frame, except when multiple returns are involved.
>> In that case, it is true that L->top is used to pass information
>> strictly between two consecutive VM instructions. (From either
>> OP_CALL/OP_VARARG to one of OP_CALL/OP_RETURN/OP_SETLIST.)
>>
>
> Would it be possible to point me to small test snippets of code that
> exercise each of these scenarios? I would like to step through those
> to see how this works in practice.
>

I think following illustrate the VARARG case?

VARARG to CALL

function y(...) print(...) end

VARARG to RETURN

function y(...) return ... end

VARARG to SETLIST

function y(...) local t={ ... } return t end


Regards