On Fri 18 Sep 2020 05:30:06 PM CEST, Greg Kurz wrote: >> qcow2_do_open correctly sets errp on each failure path. So, we can >> simplify code in qcow2_co_invalidate_cache() and drop explicit error >> propagation. We should use ERRP_GUARD() (accordingly to comment in >> include/qapi/error.h) together with error_append() call which we add to >> avoid problems with error_fatal. >> > > The wording gives the impression that we add error_append() to avoid problems > with error_fatal which is certainly not true. Also it isn't _append() but > _prepend() :) > > What about ? > > "Add ERRP_GUARD() as mandated by the documentation in include/qapi/error.h > to avoid problems with the error_prepend() call if errp is > &error_fatal."
I had to go to the individual error functions to see what "it doesn't work with &error_fatal" actually means. So in a case like qcow2_do_open() which has: error_setg(errp, ...) error_append_hint(errp, ...) As far as I can see this works just fine without ERRP_GUARD() and with error_fatal, the difference is that if we don't use the guard then the process exists during error_setg(), and if we use the guard it exists during the implicit error_propagate() call triggered by its destruction at the end of the function. In this latter case the printed error message would include the hint. Berto
