Question about GCC / GDC / LDC syntax of inline asm advanced

[Cecil Ward]

On Friday, 7 July 2023 at 21:58:20 UTC, Cecil Ward wrote:
> On Friday, 7 July 2023 at 19:45:19 UTC, Iain Buclaw wrote:
>> On Friday, 7 July 2023 at 15:25:32 UTC, Cecil Ward wrote:
>>> On Friday, 7 July 2023 at 12:18:47 UTC, Cecil Ward wrote:
>>>> On Friday, 7 July 2023 at 11:39:44 UTC, Iain Buclaw wrote:
>>>>> [...]
>>>>
>>>> Many thanks Iain. I am not doing a full parse so I shall 
>>>> simply have to warn the user that the ternary operator must 
>>>> be resolved at ctfe before I get the resulting string, and 
>>>> otherwise I have to forbid it, because for me, aside from 
>>>> detecting labels, I am treating colon as a section 
>>>> terminator. My kludge. But I don’t have months to spend.
>>>
>>> Iain, what’s the lex syntax for a label in the asm ? is it 
>>> always alphanum+ ‘:’ - something like that?
>>
>> Where is the label being referenced/defined from?
>>
>> Within the asm insn string? [GNU As documents it 
>> as](https://sourceware.org/binutils/docs/as/Symbol-Names.html):
>>
>>     [A-Za-z._][0-9A-Za-z._]+
>>
>> For a label referenced from an asm statement (goto labels 
>> section)? Then it's the same as any other D 
>> [Identifier](https://dlang.org/spec/lex.html#Identifier) - 
>> same as above, but also includes unicode alpha characters.
>
> I’m thinking it’s within the asm string. Not one mentioned in 
> the labels section. I’m trying to remember the syntax of local 
> labels from the days of my youth when I was a full-time pro asm 
> programmer, various different machines back then.

My kludge is to say that if a label is at the start of a line 
(bar any whitespace preceding it) then there must be at least one 
non-whitespace character before the colon. The section delimiter 
colon that is the start of the first constraints block is at the 
start of the line, so I test whether or not (apart from 
whitespace) a colon is seen at the start of a line, and that then 
distinguishes between a label and a ‘global’ end of main asm 
section marker. I also now check for "? :" expressions in an 
extremely shoddy fashion, even handling nested ternary 
expressions by ‘?’-counting and I can now see that a ‘:’ is not a 
main section terminator when it is in a ‘? :’. So I’m knocking 
off the cases as you and I find them. In every case, doing the 
minimum, not with a full expression grammar.