[Bug binutils/25750] GNU as has inconsistent behavior when expanding .macro that takes as input directives with arguments

[i at maskray dot me]

https://sourceware.org/bugzilla/show_bug.cgi?id=25750

--- Comment #11 from Fangrui Song <i at maskray dot me> ---
(In reply to Nick Clifton from comment #9)
> (In reply to Jian Cai from comment #8)
> Hi Jian,
> 
> > .macro foo insn1 insn2
> > \insn1
> > \insn2
> > .endm
> > 
> > foo .section .sec1, .section .sec2
>  
> It occurs to me that we might be able to achieve something like this,
> if we extend the macro argument syntax to include a definition of the
> argument separator.  For example:
> 
>   .macro foo insn1:sep, insn2:vararg
>   \insn1
>   \insn2
>   .endm
> 
> This would tell the macro processor that insn1 takes all characters up to 
> (but excluding) the next comma character and that insn2 takes the rest of
> the line (starting at the first non-whitespace character after the comma).
> 
> The new syntax "<arg>:sep<char>" tells the macro processor that argument
> <arg> is separated from the next argument by the <char> character, and only
> by the <char> character, so that any other character (apart from line ending
> characters) forms part of <arg>.
> 
> This syntax does not exist *yet*.  I am going to have a look at implementing
> it, but if it is too difficult I will give up.
> 
> What do you think - would this change provide the functionality that you
> desire ?
> 
> Cheers
>   Nick

Hi Nick, for Jian's request, we can probably just quote the arguments

 .macro foo insn1 insn2
 \insn1
 \insn2
 .endm

- foo .section .sec1, .section .sec2
+ foo ".section .sec1", ".section .sec2"

We need to document it, though.

> Comment 10
> There is one feature not documented in 
> https://sourceware.org/binutils/docs/as/Macro.html For a string literal 
> argument, gas will remove the quotes when evaluation the argument.

I am a bit concerned that the :sep qualifier will not be accurate, either.
do_scrub_chars() can squeeze a run of spaces or delete some spaces arbitrarily.
The :sep argument will not be a sole separator as spaces/commas can be
separators as well.


% x86_64-linux-gnu-as a.s && objdump -s 
 0000 612c6220 28632064 292c65             a,b (c d),e
% aarch64-linux-gnu-as a.s && objdump -s
...
 0000 612c6228 63206429 2c65               a,b(c d),e

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