[PATCH 4/4] rtems-debugger-target.c: Fix Coverity Dereference before null check

[Gedare Bloom]

On Thu, Feb 11, 2021 at 2:37 PM Chris Johns <chrisj at rtems.org> wrote:
>
>
>
> On 12/2/21 8:35 am, Gedare Bloom wrote:
> > On Thu, Feb 11, 2021 at 2:33 PM Joel Sherrill <joel at rtems.org> wrote:
> >>
> >>
> >>
> >> On Thu, Feb 11, 2021 at 3:29 PM Chris Johns <chrisj at rtems.org> wrote:
> >>>
> >>> On 12/2/21 8:16 am, Gedare Bloom wrote:
> >>>> On Thu, Feb 11, 2021 at 2:00 PM Chris Johns <chrisj at rtems.org> wrote:
> >>>>>
> >>>>> On 12/2/21 7:27 am, Ryan Long wrote:
> >>>>>> Fixes CID #1468682 where target is dereferenced before it has been
> >>>>>> checked as to whether it is null or not in the
> >>>>>> rtems_debugger_target_swbreak_control function.
> >>>>>> ---
> >>>>>>  cpukit/libdebugger/rtems-debugger-target.c | 5 +++--
> >>>>>>  1 file changed, 3 insertions(+), 2 deletions(-)
> >>>>>>
> >>>>>> diff --git a/cpukit/libdebugger/rtems-debugger-target.c b/cpukit/libdebugger/rtems-debugger-target.c
> >>>>>> index e495170..3726a6c 100644
> >>>>>> --- a/cpukit/libdebugger/rtems-debugger-target.c
> >>>>>> +++ b/cpukit/libdebugger/rtems-debugger-target.c
> >>>>>> @@ -171,17 +171,18 @@ int
> >>>>>>  rtems_debugger_target_swbreak_control(bool insert, DB_UINT addr, DB_UINT kind)
> >>>>>>  {
> >>>>>>    rtems_debugger_target*         target = rtems_debugger->target;
> >>>>>> -  rtems_debugger_target_swbreak* swbreaks = target->swbreaks.block;
> >>>>>>    size_t                         swbreak_size;
> >>>>>>    uint8_t*                       loc = (void*) addr;
> >>>>>>    size_t                         i;
> >>>>>>    int                            r;
> >>>>>>
> >>>>>> -  if (target == NULL || swbreaks == NULL || kind != target->breakpoint_size) {
> >>>>>> +  if (target == NULL || target->swbreaks.block == NULL ||
> >>>>>> +      kind != target->breakpoint_size) {
> >>>>>>      errno = EIO;
> >>>>>>      return -1;
> >>>>>>    }
> >>>>>>
> >>>>>> +  rtems_debugger_target_swbreak* swbreaks = target->swbreaks.block;
> >>>>>
> >>>>> The debug server does not declare local vars in the body of functions. I would
> >>>>> prefer the this code base stays that way if that is OK?
> >>>>>
> >>>> Good catch. This is a holdover from ANSI C that we should generally
> >>>> adhere to in RTEMS cpukit code for historical reasons.
> >>>
> >>> Yes I agree. I understand and accept this is a personal thing and I stated my
> >>> preference in the other post.
> >>
> >>
> >> No. I missed that you wanted the variable at the top of scope. I agree that
> >> tighter scoping is more a C++ thing than a C thing.  I was looking for something
> >> more complicated.
> >>>
> >>>
> >>> I use this feature judicially in C++ where I think it is more important to do
> >>> so. In C++ a variable can be declared in a number of ways and places and I feel
> >>> being consistent aids readability. Compilers are smart enough to figure out when
> >>> a variable become active and we do not need to help.
> >>
> >>
> >> It is nice when a temporary variable is only used inside an if or loop.
> >>
> >
> > It is naughty when a block variable shadows a different local variable
> > (or a global). So there are pros/cons, as usual.
>
> There is a warning for this. I thought it was on. Is it?
>
Probably. I'm just waxing philosophical. #bikeshed

> Chris