[PATCH] gas: Document @ and % as interchangeable for type argument in .section

[Jan Beulich]

On 18.05.2026 15:00, Will Hawkins wrote:
> On Mon, May 18, 2026 at 1:57 AM Jan Beulich <jbeulich@suse.com> wrote:
>> On 17.05.2026 13:35, Will Hawkins wrote:
>>> On Sunday, May 17, 2026, Will Hawkins <hawkinsw@obs.cr> wrote:
>>>> On Sunday, May 17, 2026, Jan Beulich <jbeulich@suse.com> wrote:
>>>>> On 16.05.2026 02:38, Will Hawkins wrote:
>>>>>> In the .section Assembler Directive for the ELF format, both the % and
>>>>>> the @ can be used when writing the type argument.
>>>>>
>>>>> That's not exactly true (the two aren't fully interchangeable), and hence
>>>>> ...
>>>>
>>>>
>>>>
>>>> In obj-elf.c, I saw
>>>>
>>>> else if (c == '@' || c == '%')
>>>>
>>>> which I must have misinterpreted?
>>>
>>> I guess that they are only treated equivalently in code on platforms where
>>> the @ and % do not have implications for the code in earlier processing
>>> before reaching obj_elf_section.
>>
>> Correct, comments are being removed much earlier. (If they were fully
> 
> I am glad that my reading of the code was not wildly inaccurate: _If_
> there were no preprocessor implications for those characters, then
> they would be equivalent.
> 
>> equivalent, in that testcase of yours you also wouldn't have had to
>> switch from @ to %.)
> 
> Yes, I agree.
> 
> Before I propose an alternate, I figured it might be worth describing
> why I wanted to make the change in the first place:
> 
> My local system is an x86-64. When I started developing a test case
> for objdump and I was running the testsuite, the test in objdump.exp
> based on the code in dw5-op.S passed. I could read the documentation
> and see that @progbits should be the syntax.
> 
> I interpreted the existing note to imply mutually exclusive options
> for @ vs %. And yet the test was passing. I used as to compile it --
> just to be sure. Once I dug into the code and saw the aforementioned
> if statement, I realized _why_ the test author used %: because % is
> not a comment indicator on x86-64, using the % means that one version
> of the test code works for both x86-64 and ARM platforms.
> 
> I proposed the change so that others would not have to search as much
> as I did. With that as background, would you be amenable to rewriting
> 
> Note on targets where the @ character is the start of a comment (eg
> ARM) then another character is used instead. For example the ARM port
> uses the % character.
> 
> to
> 
> Note - certain targets treat @ as the start of a comment (e.g., ARM).
> On such platforms, % is used instead. On platforms where neither @ nor
> % indicate the start of a comment, @ and % may be used
> interchangeably.

This reads okay to me.

Jan