Re: [Qemu-devel] [PATCH RFC 0/3] error: allow local errors to trigger abort

[Michael S. Tsirkin]

On Wed, Jun 17, 2015 at 10:26:26AM -0400, John Snow wrote:
> 
> 
> On 06/16/2015 08:53 AM, Michael S. Tsirkin wrote:
> >     
> >     It's a common idiom:
> >     
> >         Error *local_err = NULL;
> >         ....
> >         foo(&local_err);
> >         ...
> >         if (local_err) {
> >             error_propagate(errp, local_err);
> >             return;
> >         }
> >     
> >     Unfortunately it means that call to foo(&local_err) will
> >     not abort even if errp is set to error_abort.
> >     
> >     Instead, we get an abort at error_propagate which is too late.
> >     
> 
> Please humor the ignorant: Why is this too late? Any code that does
> anything between foo(&local_err) and error_propagate is already broken.

We have lost the stack so it's hard to debug. v2 explains it better.

> >     To fix, add an API to check errp and set local_err to error_abort
> >     if errp is error_abort.
> > 
> > Michael S. Tsirkin (3):
> >   error: don't rely on pointer comparisons
> >   error: allow local errors to trigger abort
> >   block/nfs: switch to error_init_local
> > 
> >  include/qapi/error.h |  5 +++++
> >  block/nfs.c          |  2 +-
> >  util/error.c         | 21 ++++++++++++++++-----
> >  3 files changed, 22 insertions(+), 6 deletions(-)
> >