Re: [Tinycc-devel] bounds checking with tcc

[Michael Matz]

Hello again,

but to maybe be a bit more constructive:

On Thu, 28 Nov 2019, Michael Matz wrote:

> > I fixed this with some push/pop trickery.

I see, yeah, expanding calls during calls is broken as gfunc_call in the 
generators doesn't generally leave a trace in vtop[] which registers are 
currently holding values.  I think you only need so push/pop si/di, as 
cx/dx aren't used intentionally during reg-param setup.

(I think i386-gen.c has a simila bug with fastcall functions).

> > This probably could be 
> > improved. I have now added a minimum patch so bounds checking works a 
> > little bit. We need still to fix the shared lib reloc problems and the 
> > malloc/free hooks.
> 
> Do we?  Can we perhaps also simply declare bounds checking to work only 
> with the main executable?  Or remove that whole feature altogether?

And perhaps another compromise: only conditionally enable tracking of 
locals: Invent a new cmdline option (say, '-bb'), which sets 
do_bounds_checking to 2.  And only if it's > 1 you would also track 
locals, whereas with == 1 you would only track arrays and structs.

Your decision, I think you can push this patch either with that change, or 
without (but try to remove cx/dx from the push/pop).  It doesn't make tccs 
source code larger or uglier in any meaningful way, but does fix practical 
bugs.


Ciao,
Michael.