lldb-mi should never be checking the children. This is never a good idea due to
performance. What happens when you have an array with a million entries? Long
delay. Aggregate types should never say they changed. Only SBValue objects that
have values should claim to change.
Greg
> On Aug 25, 2017, at 10:42 AM, Ted Woodward via lldb-dev
> <lldb-dev@lists.llvm.org> wrote:
>
> I found a hang in lldb-mi's -var-update. It checks to see if a var changed,
> then it checks each of the children recursively. If a child is a pointer
> back to a parent, as in this case:
>
> struct complex_type
> {
> int i;
> struct { long l; } inner;
> struct complex_type *complex_ptr;
> };
>
> void
> var_update_test(void)
> {
> struct complex_type complx_array[2];
>
> complx_array[0].i = 4;
> complx_array[0].inner.l = 4;
> complx_array[0].complex_ptr = &complx_array[1];
> complx_array[1].i = 5;
> complx_array[1].inner.l = 5;
> complx_array[1].complex_ptr = &complx_array[0];
>
>
>
> the code in CMICmdCmdVarUpdate::ExamineSBValueForChange will get into an
> infinite loop.
>
> const MIuint nChildren = vrwValue.GetNumChildren();
> for (MIuint i = 0; i < nChildren; ++i) {
> lldb::SBValue member = vrwValue.GetChildAtIndex(i);
> if (!member.IsValid())
> continue;
>
> if (member.GetValueDidChange()) {
> vrwbChanged = true;
> return MIstatus::success;
> } else if (ExamineSBValueForChange(member, vrwbChanged) && vrwbChanged)
> // Handle composite types (i.e. struct or arrays)
> return MIstatus::success;
> }
>
> I've got a patch that disables checking a pointer's children. I'll put it up
> on phabricator today.
>
> Ted
>
> --
> Qualcomm Innovation Center, Inc.
> The Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a
> Linux Foundation Collaborative Project
>
>
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