Re: [PATCH][gdb/testsuite] Add .debug_loc support in dwarf assembler

[Tom de Vries via Gdb-patches <gdb-patches@sourceware.org>]

On 10/14/21 3:32 PM, Simon Marchi wrote:
>> diff --git a/gdb/testsuite/lib/dwarf.exp b/gdb/testsuite/lib/dwarf.exp
>> index 66f9844fe2e..a15eacfb46c 100644
>> --- a/gdb/testsuite/lib/dwarf.exp
>> +++ b/gdb/testsuite/lib/dwarf.exp
>> @@ -2369,6 +2369,102 @@ namespace eval Dwarf {
>>  	aranges_end:
>>      }
>>  
>> +    # Emit a .debug_loc entry.
>> +
>> +    proc loc_entry { start end location_description } {
>> +	# Determine how to emit addresses.
>> +	variable _addr_size
>> +	if { $_addr_size == 8 } {
>> +	    set addr_op .8byte
>> +	} elseif { $_addr_size == 4 } {
>> +	    set addr_op .4byte
>> +	}
>> +
>> +	# Emit start and end address.
>> +	_op $addr_op $start "Start address"
>> +	_op $addr_op $end "End address"
>> +
>> +	declare_labels location_description_start
>> +	declare_labels location_description_end
>> +
>> +	# Emit length of location description.
>> +	set len "$location_description_end - $location_description_start"
>> +	_op .2byte $len "Location description length"
>> +
>> +	# Tag start of location description.
>> +	define_label $location_description_start
>> +
>> +	# Emit location description.
>> +	variable _cu_version
>> +	variable _cu_offset_size
>> +	_location $location_description $_cu_version $_addr_size \
>> +	    $_cu_offset_size
>> +
>> +	# Tag end of location description.
>> +	define_label $location_description_end
>> +    }
>> +
>> +    # Emit a DWARF .debug_loc contribution.
>> +    #
>> +    # OPTIONS is a list with an even number of elements containing
>> +    # option-name and option-value pairs.
>> +    # Current options are:
>> +    # cu_is_64 0|1 - boolean indicating if references from location
>> +    #                descriptions refer to a 64-bit DWARF CU.
>> +    #                default = 0 (32-bit)
>> +    # cu_version n - section version of DWARF CU referenced from location
>> +    #                descriptions.
>> +    #                default = 4
>> +    #
>> +    # BODY is Tcl code that emits the parts which make up the body of
>> +    # the debug_loc contribution.  It is evaluated in the caller's context.
>> +    # The following command is available for the BODY section:
>> +    #
>> +    #   loc_entry <start> <end> <location description>
>> +    #     -- emit a .debug_loc entry
>> +
>> +    proc loc { options body } {
> 
> I would suggest using the same trick as used for rnglists: rename
> loc_entry to _loc_entry (or something like that, to show it's
> internal).  And use:
> 
> 	with_override Dwarf::entry Dwarf::_loc_entry {
> 	    uplevel $body
> 	}
> 
> Users would then look like:
> 
>     loc { ... } {
> 	entry 0x123 0x456 {
> 	    ...
>         }
>     }
> 
> I think that looks good: because you are in the "loc" context, it is
> obvious enough that entry is a location list entry.  I think that makes
> it easy to write.
> 

Ack, updated that way, thanks for the tip.

> I would have suggested renaming "loc" to "loclist", because this is
> actually generating a "location list", according to the standard.  But
> that might become confusing with the DWARF5 "loclists"...
> 

Ack.  FWIW, I chose the name based on the .debug_loc section, similar to
how .debug_aranges are generated use a proc aranges.

> But other than that, the patch LGTM.
> 

Committed.

Thanks,
- Tom