Re: [PATCH 04/11] gdb: use intrusive list for step-over chain

[Simon Marchi via Gdb-patches <gdb-patches@sourceware.org>]

On 2021-07-05 11:45 a.m., Pedro Alves wrote:
> On 2021-06-22 5:56 p.m., Simon Marchi via Gdb-patches wrote:
> 
>> 	* reference-to-pointer-iterator.h (struct
>> 	reference_to_pointer_iterator): Add default assignment
>> 	operators.
> 
> It's not immediately obvious why this is needed now, and wasn't before.
> It should perhaps be mentioned in the commit log.  Especially if you
> decide to discard the ChangeLog entry.
> 
> Otherwise LGTM.

Hmm right.  It's to avoid this error:

      CXX    infrun.o
    cc1plus: warning: command-line option ‘-Wmissing-prototypes’ is valid for C/ObjC but not for C++
    In file included from /home/simark/src/binutils-gdb/gdb/breakpoint.h:36,
		     from /home/simark/src/binutils-gdb/gdb/gdbthread.h:26,
		     from /home/simark/src/binutils-gdb/gdb/infrun.h:21,
		     from /home/simark/src/binutils-gdb/gdb/infrun.c:23:
    /home/simark/src/binutils-gdb/gdb/../gdbsupport/safe-iterator.h: In instantiation of ‘basic_safe_iterator<Iterator>::self_type& basic_safe_iterator<Iterator>::operator++() [with Iterator = reference_to_pointer_iterator<intrusive_list_iterator<thread_info, intrusive_member_node<thread_info, &thread_info::step_over_list_node> > >; basic_safe_iterator<Iterator>::self_type = basic_safe_iterator<reference_to_pointer_iterator<intrusive_list_iterator<thread_info, intrusive_member_node<thread_info, &thread_info::step_over_list_node> > > >]’:
    /home/simark/src/binutils-gdb/gdb/infrun.c:1883:26:   required from here
    /home/simark/src/binutils-gdb/gdb/../gdbsupport/safe-iterator.h:82:10: error: use of deleted function ‘constexpr reference_to_pointer_iterator<intrusive_list_iterator<thread_info, intrusive_member_node<thread_info, &thread_info::step_over_list_node> > >& reference_to_pointer_iterator<intrusive_list_iterator<thread_info, intrusive_member_node<thread_info, &thread_info::step_over_list_node> > >::operator=(const reference_to_pointer_iterator<intrusive_list_iterator<thread_info, intrusive_member_node<thread_info, &thread_info::step_over_list_node> > >&)’
       82 |     m_it = m_next;
	  |     ~~~~~^~~~~~~~
    In file included from /home/simark/src/binutils-gdb/gdb/thread-iter.h:25,
		     from /home/simark/src/binutils-gdb/gdb/gdbthread.h:516,
		     from /home/simark/src/binutils-gdb/gdb/infrun.h:21,
		     from /home/simark/src/binutils-gdb/gdb/infrun.c:23:
    /home/simark/src/binutils-gdb/gdb/../gdbsupport/reference-to-pointer-iterator.h:30:8: note: ‘constexpr reference_to_pointer_iterator<intrusive_list_iterator<thread_info, intrusive_member_node<thread_info, &thread_info::step_over_list_node> > >& reference_to_pointer_iterator<intrusive_list_iterator<thread_info, intrusive_member_node<thread_info, &thread_info::step_over_list_node> > >::operator=(const reference_to_pointer_iterator<intrusive_list_iterator<thread_info, intrusive_member_node<thread_info, &thread_info::step_over_list_node> > >&)’ is implicitly declared as deleted because ‘reference_to_pointer_iterator<intrusive_list_iterator<thread_info, intrusive_member_node<thread_info, &thread_info::step_over_list_node> > >’ declares a move constructor or move assignment operator
       30 | struct reference_to_pointer_iterator
	  |        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~

So I would say:

  Add explicit default assignment operators to
  reference_to_pointer_iterator, which are otherwise implicitly deleted.
  This is needed because to define thread_step_over_list_safe_iterator,
  we wrap reference_to_pointer_iterator inside a basic_safe_iterator,
  and basic_safe_iterator needs to be able to copy-assign the wrapped
  iterator.  The move-assignment operator is therefore not needed, only
  the copy-assignment operator is.  But for completeness, add both.

Simon