CPP preprocessor: #define-splitting?

CPP preprocessor: #define-splitting?

[Florian Stoehr]

Hi,

I'm developing a gcc-compatible preprocessor for a compiler project. While
doing this, I discovered something strange.

In preprocessor documentation:

    /\
     *
     */ # /*
     */ defi\
     ne FO\
     O 10\
     20


will expand to "#define FOO 1020". It does.

But:

# /*
*/ define TEST "foo"

--> #define TEST "foo"

Replacing the "#" by an "X" will produce with gcc -E:

X
 define TEST "foo"


_BUT_:
#
 define TEST "foo"

--> TEST doen't get defined.

The problem is: Why does it recognize the "#" and "define" splitted by a
multi-line comment as "#define"? Is this the correct behaviour?

Thanks for your help
Florian

Re: CPP preprocessor: #define-splitting?

[Eljay Love-Jensen]

Hi Florian,

The # is a preprocessor directive.

The X is not a preprocessor directive.

The rules for parsing preprocessor directives is different form the rules 
for parsing non-preprocessor directives.  (The state machine is in a 
different state.)

HTH,
--Eljay

Re: CPP preprocessor: #define-splitting?

[Florian Stoehr]

On Wed, 25 Aug 2004, Eljay Love-Jensen wrote:

> Hi Florian,
>
> The # is a preprocessor directive.
>
> The X is not a preprocessor directive.
>
> The rules for parsing preprocessor directives is different form the rules
> for parsing non-preprocessor directives.  (The state machine is in a
> different state.)
>
> HTH,
> --Eljay
>
>

Hi,

thanks for the reply. But there seems to happen something strange BEFORE
the preprocessing itself (in comment remove stage?).

Why am I allowed to do a...

# /*
*/ define

and a

#
 define

not? I thought the stage where it strips out comments comes before the
"main" preprocessor where it scans for #-directives. so why is the #
define allowed to be split on multiple lines WITHOUT a backslash-newline?

afaik, any comment gets replaced by a single " " and every newline inside
the comment gets added AFTER the comment.

so the

# /*
*/ define

should become a

#
 define

after the comment removing stage - but this does not work see above.

(just confused wheter it does something special with comments "inside" a
#-directive)

-Florian