Re: [PATCH][gdb/testsuite] Don't use default form in Dwarf::_guess_form

[Tom de Vries <tdevries@suse.de>]

On 10/23/20 5:12 PM, Simon Marchi wrote:
> On 2020-10-23 7:46 a.m., Tom de Vries wrote:
>> Hi,
>>
>> The only possible form for a DW_AT_low_pc attribute is DW_FORM_addr.
>>
>> When specifying in dwarf assembly a low_pc attribute without explicit form:
>> ...
>>   {low_pc {main_label - 4}}
>> ...
>> the resulting attribute uses DW_FORM_string, which is misinterpreted by gdb
>> when reading it as:
>> ...
>>         cu->base_address = attr->as_address ();
>> ...
>>
>> Stop using DW_FORM_string as default form.  Instead, use a default form based
>> on the attribute name, if possible and unambiguous.  Otherwise, error out.
>>
>> F.i.:
>> - for DW_AT_low_pc we use DW_FORM_addr.
>> - For DW_AT_high_pc, we don't specify a default form because it could be
>>   either address or constant class.
>> - For DW_AT_name, we use DW_FORM_string.  While we could encode with
>>   DW_FORM_strp instead, DW_FORM_string is always ok.
>>
>> Tested on x86_64-linux.
>>
>> Any comments?
>>
>> Thanks,
>> - Tom
> 
> I like it, I like specifying explicit forms in any case.
> 
> I think it makes the "If the value looks like an integer, a form is
> required." redundant though.  You could remove it, in which case
> specifying an integer attribute without a form would fall in the "No
> form for..." error branch.

Done, and committed.

Thanks,
- Tom