Re: [Qemu-devel] [PATCH 2/2] PPC: Fail on leaking temporaries

[Peter Maydell]

On 19 January 2014 20:15, Alexander Graf <address@hidden> wrote:
> On 19.01.2014, at 17:51, Peter Maydell <address@hidden> wrote:
>> Exiting is pretty harsh; ARM just warns and continues.

> Well, the check only ever happens when QEMU gets compiled
> with --enable-debug-tcg, so I figured it's easier for me to catch
> new problems or problems with unit tests if we get a harsh abort :).

Well, you're the one that gets to field the bug reports for PPC so
it's your call :-)

Longer term I was wondering if we should define the concept
of a 'scope object' for TCG temporaries, so you create a scope
object and then we have versions of tcg_temp_new_*() that
take a scope object to effectively define the lifetime of that
temp. Destroying the scope object frees every TCG temp in it.
Then we could just have the target frontends create a scope
for each instruction, and they wouldn't need to worry about
manually freeing TCG temporaries within it at all. That seems
better than the current approach where every frontend rolls
its own auto-free mechanism, and would render this sort of
"check for bugs in manual temp freeing" unnecessary too.

(We could also make the tcg_gen_brcond* functions do a
"free all temps in all scope objects" and then we'd catch
use-of-temp-after-branch bugs, especially if we also got
TCG to assert on use of a dead temporary rather than only
later when it was doing regalloc on it...)

thanks
-- PMM