Re: [PATCH 3/3] btrace: Remove ui_out cleanups

[Simon Marchi <simon.marchi@polymtl.ca>]

On 2018-03-05 07:39, Metzger, Markus T wrote:
> Hello Simon,
> 
> 
>> This patch replaces the cleanups that close the list and tuple of the
>> btrace instruction history output with ui_out_emit_tuple and
>> ui_out_emit_list.
>> 
>> This allows removing make_cleanup_ui_out_tuple_begin_end and
>> make_cleanup_ui_out_list_begin_end.
>> 
>> This patch (along with the previous ones in the series) was regtested 
>> on
>> the buildbot.
> 
> 
>> diff --git a/gdb/record-btrace.c b/gdb/record-btrace.c
>> index 15ce760f5a..ddd15c4781 100644
>> --- a/gdb/record-btrace.c
>> +++ b/gdb/record-btrace.c
>> @@ -620,26 +620,25 @@ btrace_find_line_range (CORE_ADDR pc)
>> 
>>  static void
>>  btrace_print_lines (struct btrace_line_range lines, struct ui_out 
>> *uiout,
>> -		    struct cleanup **ui_item_chain, int flags)
>> +		    gdb::optional<ui_out_emit_tuple> *src_and_asm_tuple,
>> +		    gdb::optional<ui_out_emit_list> *asm_list,
> 
> Reference instead of pointer?

I once pointed this out on one of Tom's patches, and he said that in the 
caller code, it's more obvious that object is meant to be modified if 
you do:

   function_that_modifies_object (&object);

instead of

   function_that_modifies_object (object);

And I kind of agree with that it is, which is why I've been using 
pointers when references would have worked (ok, here the function name 
makes it obvious but it's not always the case).  In the implementation 
of the function, since you use object->field instead of object.field, it 
also hints that you're not modifying a local object.  But I also agree 
that it's really not C++-y to do it this way, so I'll happily change it.

>> -  for (line = lines.begin; line < lines.end; ++line)
>> +  for (int line = lines.begin; line < lines.end; ++line)
>>      {
>> -      if (*ui_item_chain != NULL)
>> -	do_cleanups (*ui_item_chain);
>> +      asm_list->reset ();
>> +      src_and_asm_tuple->reset ();
> 
> The SRC_AND_ASM_TUPLE reset () shouldn't be necessary; it is reset ()
> in emplace ().

Ok.

>> -      *ui_item_chain
>> -	= make_cleanup_ui_out_tuple_begin_end (uiout, "src_and_asm_line");
>> +      src_and_asm_tuple->emplace (uiout, "src_and_asm_line");
>> 
>>        print_source_lines (lines.symtab, line, line + 1, psl_flags);
>> 
>> -      make_cleanup_ui_out_list_begin_end (uiout, "line_asm_insn");
>> +      asm_list->emplace (uiout, "line_asm_insn");
>>      }
>>  }
> 
> Looks good to me, otherwise.
> 
> I have not tested it, though.  Did you run the gdb.btrace test suite?  
> You said
> you ran buildbot but that might skip gdb.btrace when run on VMs or on 
> old
> hardware.
> 
> Please let me know if you want me to run the gdb.btrace tests for you.  
> A user
> branch would be nice in that case.

Yes, I have ran the gdb.btrace/*.exp tests locally on two different 
machines and saw no regressions.  However, the processors may be a bit 
old (Q6600 from 2007 and i5-4310U from 2014), so it's possible that not 
all required features are available, and therefore some tests may be 
skipped.  So if you want to be sure, here's a branch for you to test:

users/simark/btrace-cleanups
https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;a=shortlog;h=refs/heads/users/simark/btrace-cleanups

Thanks!

Simon