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Index > Compiler Internals > [?bug] fasmg: difference in namespace symbol definitions

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bitRAKE



Joined: 21 Jul 2003
Posts: 3976
Location: vpcmipstrm
bitRAKE 14 Aug 2023, 03:10
I don't know if this is a bug or an error in my understanding.
Code:
TRY_BUG = 0

macro Named?
        display 'instruction',10
end macro

define scope scope ; searchable namespace

if TRY_BUG
        define scope.?named Named
else
        namespace scope
                define ?named Named
        end namespace ; scope
end if

calminstruction (instruction) intercept
        local line
        arrange line, instruction
        ; need to remove the leading ?
        transform line, scope
        jno unknown
        display 'intercepted '
        assemble line
        exit
unknown:
        err 'unknown instruction'
end calminstruction


        named ; execute instruction

        ?named intercept    
... normally, we would just define another MACRO which executes the first definition after intercept. In this particular instance I wanted to flag the instruction usage to indicate the "out of spec" usage. So, I got the idea to proceed it with a "?" which would be stripped. This also allows me to intercept a number of instructions in a similar way.

I'm happy to use the explicit NAMESPACE syntax to get this "feature", but if it shouldn't exist then it could just disappear in the future. So, I hope it remains a "feature" even though DEFINE seems to consume the "?"? Very Happy

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¯\(°_o)/¯ “languages are not safe - uses can be” Bjarne Stroustrup
Post 14 Aug 2023, 03:10
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Tomasz Grysztar



Joined: 16 Jun 2003
Posts: 8346
Location: Kraków, Poland
Tomasz Grysztar 14 Aug 2023, 07:20
As it is currently specified by documentation, you can prepend "?" to a whole identifier, not to a name inside the identifier. Therefore the one inside of an identifier is not expected to be followed by a name and as such it is an incorrect syntax that causes the identifier parsing to be aborted. This in turn results in a side-effect of splitting the DEFINE on unexpected boundaries. The DEFINE syntax is quirky (compared to EQU, for example) - it's inherited from fasm 1, but does not play well with fasmg's engine. I could perhaps change it to require whitespace between the identifier and the value - even though it would differ from fasm 1, it would certainly be more intuitive.
Post 14 Aug 2023, 07:20
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bitRAKE



Joined: 21 Jul 2003
Posts: 3976
Location: vpcmipstrm
bitRAKE 14 Aug 2023, 09:06
Thank you, that makes sense. EQU does produce the error, and it's documented behavior. I do remember "?" not being allowed in the middle. So, the corner case is just in the DEFINE quirkiness not producing the error that EQU does.

One potential example would be an implementation of the concept Jin X presented - kind of an auto epilog. It could be given a snazzy syntax, and reading the code later - I think the question mark would slow me down - that and the missing label.

_________________
¯\(°_o)/¯ “languages are not safe - uses can be” Bjarne Stroustrup
Post 14 Aug 2023, 09:06
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Tomasz Grysztar



Joined: 16 Jun 2003
Posts: 8346
Location: Kraków, Poland
Tomasz Grysztar 14 Aug 2023, 16:41
On a side note - you could also use the new "late interceptor" to only catch the lines that have no valid instruction, to retry after TRANSFORMing them:
Code:
calminstruction ?? line&
        transform line
        assemble line
end calminstruction

macro test
        display 'macro',10
end macro

define test display 'equ',10

test
?test    
Post 14 Aug 2023, 16:41
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