Impossible character escapes in strings

[ISSOtm]

I have a simple macro:

dstr: MACRO
    REPT _NARG
        db \1
        shift
    ENDR
    db 0
ENDM

And I pass it this string:

    dstr "Line 1\nLine 2"

And I get this error:

ERROR: engine.asm(7) -> engine/title.asm(1357) -> dstr(3) -> dstr(1):
    Unterminated string

I then try to pass this string instead:

    dstr "Line1\\\nLine2"

And I get this error:

ERROR: engine.asm(7) -> engine/title.asm(1357) -> dstr(3) -> dstr(1):
    Illegal character escape '
'

I would expect either of these variants to work, since they're right there in the manual!

[ISSOtm]

Well, I figured out that the correct answer was \\n. Which both isn't intuitive and not really pointed to in the manual. Plus the Unterminated string error doesn't give much insight as to what to do - I only knew what to do because I had encountered it using commas.

[AntonioND]

Well, it makes sense. The \\ is converted to \ after the first pass. If you do the same to the n, \n will be converted to a newline.

Where is the problem in the manual?

I agree that the error messages aren't always helpful, but it's quite hard to get the parser to say useful things in some cases...

[ISSOtm]

Well, the manual states that \, is an escape sequence, so when I got an Unterminated string error after using a comma, I thought of escaping it. But I expected \n to work as well, which it didn't.

In retrospect, \\n does make sense, but it's not obvious to have the idea -- it took me a day to have that idea.

[AntonioND]

Well, I think I know what's happening.

dstr: MACRO
    REPT _NARG
        db \1
        shift
    ENDR
    db 0
ENDM

dstr "Line1\\\nLine2"

The parser sees, after the expansion:

    REPT _NARG
        db "Line1\
Line2"
        shift
    ENDR
    db 0

As far as I remember, strings can't be split into multiple lines. So yeah, there is an unterminated string there.

[ISSOtm]

That's also my guess, although the parser actually attempts to escape the line feed, instead of calling it an unterminated string. But that's just nitpicking.

[AntonioND]

However, even though this is not a bug, maybe the documentation can be updated. The documentation has an example, actually:

Line continuations work as usual inside macros or lists of arguments of macros.
Strings, however, are a bit trickier. The following example shows how to use
strings as arguments for a macro:

    PrintMacro : MACRO 
        PRINTT \1 
    ENDM 
 
        PrintMacro STRCAT(\"Hello\"\,  \ 
                          \" world\\n\")

Maybe it's just in the wrong place.

[ISSOtm]

I think it is. It also feels weird to have to escape everything, because there are no quotes wrapping the argument. Intuitively, it feels like you shouldn't have to escape those...

[AntonioND]

Well, that's a macro argument, and macro arguments are a tricky thing...

The problem is that the parser isn't great and there are many hacks everywhere. This is a problem that isn't going to go away.

The only thing I can do is to change the docs, but I don't know where to put that, so I'm open for suggestions.

[AntonioND]

RE: They are tricky things: #63

[AntonioND]

I'm going to close this. If you have a suggestion on how to change the docs feel free to propose it.