Peter Maydell <peter.mayd...@linaro.org> writes:
> This is something clang's -fsanitize=undefined spotted. The
> code generated by qapi-commands.py in qmp-marshal.c for
> qmp_marshal_* functions where there are some optional
> arguments looks like this:
>
> bool has_force = false;
> bool force;
>
> mi = qmp_input_visitor_new_strict(QOBJECT(args));
> v = qmp_input_get_visitor(mi);
> visit_type_str(v, &device, "device", errp);
> visit_start_optional(v, &has_force, "force", errp);
> if (has_force) {
> visit_type_bool(v, &force, "force", errp);
> }
> visit_end_optional(v, errp);
> qmp_input_visitor_cleanup(mi);
>
> if (error_is_set(errp)) {
> goto out;
> }
> qmp_eject(device, has_force, force, errp);
>
> In the case where has_force is false, we never initialize
> force, but then we use it by passing it to qmp_eject.
> I imagine we don't then actually use the value, but clang
Use of FOO when !has_FOO is a bug.
> complains in particular for 'bool' variables because the value
> that ends up being loaded from memory for 'force' is not either
> 0 or 1 (being uninitialized stack contents).
>
> Anybody understand what the codegenerator is doing well enough
> to suggest a fix? I'd guess that just initializing the variable either
> at point of declaration or in an else {) clause of the 'if (has_force)'
> conditional would suffice, but presumably you need to handle
> all the possible data types...
I can give it a try. Will probably take a while, though.
