A preprocessor bug: local affected by an unrelated backslash

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l_inc

Joined: 23 Oct 2009
Posts: 881

l_inc 30 Dec 2014, 15:58

Good day and merry new year, guys!
I've just came across an unexpected behaviour:

Code:

rept 1
{
    macro m
    \{ local l
        display \`l,13,10
    \}
}
m
m

The backslash here makes local be ignored by the expansion of an external macroblock, which it shouldn't do. The problem is related to other macroblock specialized directives as well. E.g. the following snippet shouldn't compile:

Code:

rept 2
{
    macro m [a]
    \{ common
        display a,13,10
    \}
}
m 'a','b'

Identifiers however seem to be unaffected:

Code:

macro x a
{
    macro m \a
    \{a
        display \`l,13,10
    \}
}
x display 'x'
m display 'm'

The argument is correctly interpreted in the context of the macro x.

P.S. Sorry, I meant to post the report in the "Compiler Internals" subforum.

revolution says: I moved it for you

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Faith is a superposition of knowledge and fallacy

30 Dec 2014, 15:58

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 19871
Location: In your JS exploiting you and your system

revolution 30 Dec 2014, 16:31

Indeed, using Egyptian brackets gives a different result

Code:

rept 1
{
    macro m \{
    local l
        display \`l,13,10
    \}
}
m
m

30 Dec 2014, 16:31

evk1

Joined: 18 Jun 2014
Posts: 24

evk1 30 Dec 2014, 16:38

Try using backslashes with such keywords. \local \common.

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Sorry for my English

30 Dec 2014, 16:38

Tomasz Grysztar

Joined: 16 Jun 2003
Posts: 8266
Location: Kraków, Poland

Tomasz Grysztar 30 Dec 2014, 16:41

The special directives processed by macro line maker are only recognized if they are the first symbol in line (another detail probably not mentioned in the manual), otherwise they are treated as just another symbol preprocessed in a standard way. For example:

Code:

macro m {
  l: common
}

Here the "common" is not recognized by line maker because it is not a first symbol of line and so the "common" word is passed unchanged to the assembler stage. A more interesting example would be:

Code:

macro m common {
  common l: common
}
m dd l

And "{" is nothing special from the point of view of line maker, it is just another symbol that gets in the way.

30 Dec 2014, 16:41

l_inc

Joined: 23 Oct 2009
Posts: 881

l_inc 30 Dec 2014, 17:01

revolution

Quote:

revolution says: I moved it for you

l_inc says: Thank you. Smile

Tomasz Grysztar
Oh... I suppose, I overhurried to report on this one. Sorry.

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Faith is a superposition of knowledge and fallacy

30 Dec 2014, 17:01

baldr

Joined: 19 Mar 2008
Posts: 1651

baldr 31 Dec 2014, 08:39

Tomasz Grysztar,

Probably implicit line-break after opening brace would do (heh, closing brace have it).

31 Dec 2014, 08:39

l_inc

Joined: 23 Oct 2009
Posts: 881

l_inc 31 Dec 2014, 13:10

baldr

Quote:

heh, closing brace have it

I don't think there's any special handling of the closing brace, cause the following doesn't work either:

Code:

macro m [a]
{
        rept 1 \{\} common
        display a,13,10
}
m 'a','b'

It's just about the moment when the corresponding directive appears as the first token on a line.

_________________
Faith is a superposition of knowledge and fallacy

31 Dec 2014, 13:10

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