Re: [PATCH] gas: Add --force-compress-debug-sections

[Jan Beulich <jbeulich@suse.com>]

On 24.02.2023 15:57, Tom de Vries wrote:
> On 2/24/23 15:26, Jan Beulich wrote:
>> On 24.02.2023 15:11, Tom de Vries wrote:
>>> On 2/24/23 14:23, Jan Beulich wrote:
>>>> On 24.02.2023 13:21, Tom de Vries wrote:
>>>>> On 2/24/23 12:28, Jan Beulich wrote:
>>>>>> I also wouldn't see anything wrong with something
>>>>>> like "...=force,zstd,none" - the last one(s) win. That's no different
>>>>>> from specifying a second instance of the option. And without that it
>>>>>> looks as if the parsing would end up simpler.
>>>>>
>>>>> OK, gave that a try.
>>>>
>>>> That's still accumulating none and force across the entire sequence
>>>> (and then giving none priority over force, no matter that force may
>>>> have been specified last),
>>>
>>> Um, so you're saying that none+zstd+force is currently interpreted as none?
>>>
>>> Lets try:
>>> ...
>>> $ gcc ~/hello.c -c -Wa,-gdwarf-5 -Xassembler
>>> --compress-debug-sections=none+zstd+force
>>> $ readelf -S -W hello.o | grep " .debug"
>>>     [ 9] .debug_line       PROGBITS        0000a8 000064 00   C  0   0  8
>>>     [11] .debug_line_str   PROGBITS        000110 000046 01 MSC  0   0  8
>>>     [12] .debug_info       PROGBITS        000158 000046 00   C  0   0  8
>>>     [14] .debug_abbrev     PROGBITS        0001a0 000049 00   C  0   0  8
>>>     [15] .debug_aranges    PROGBITS        0001f0 000034 00   C  0   0  8
>>>     [17] .debug_str        PROGBITS        000228 00005a 01 MSC  0   0  8
>>>
>>> ...
>>>
>>> So, that doesn't seem to be the case, compression is done, as expected.
>>
>> Oh, I've overlooked that you explicitly clear *none when you set *force
>> (my attention was mainly on the bottom of parse_compress_debug_optarg()).
>> I think that's more involved than necessary (possibly merely a result of
>> you having worked incrementally from your earlier version), and less
>> obviously doing the same as would happen when multiple separate options
>> were parsed.
> 
> I've tried to simplify further.
> 
> Is this more how you want it?

I have to admit that I'm still puzzled by the presence of
finalize_parse_compress_debug_optarg() as well as you needing both a new
static variable and a new global one. But I guess whether that's really
needed first of all depends on the semantics we want e.g.

--nocompress-debug-sections --compress-debug-sections=force

to have (which, with how you have it presently, could also be expressed
as

--compress-debug-sections=none+force

or

--compress-debug-sections=none --compress-debug-sections=force

afaict). I view the present meaning as one sensible one, but I could
also see "none" (or equivalent) simply zapping the compression type
(and hence rendering "force" meaningless) as another sensible one. A
change in meaning may then also result in the three option combinations
above possibly not all doing the same.

As an aside: As you update the patch, please try to keep the title in
line with what the patch actually does.

Also, ftaod, I don't mean to stand in the way of another maintainer
approving any of the forms proposed so far. This specifically also
includes the use of '+' as a separator, which I personally don't
(currently) intend to approve.

Jan