Re: [Boost-users] [WAVE] position of tokens

8 Nov 2006

      Wow! You are fast! I have experimented a little bit with this code and
it looks very good, but there are two things which needs to be fixed
before I can use it:
    * the position of a token in the original source code is
gone(default in standard Wave)
    * the line positioning is incorrect/non-standard (see below for an
example).
The column information seems correct to me. But the line information
is not correct as it does not behave like a standard preprocessor
which would insert #line directives to map the positions to the
original source file(s). Example:
///BEGIN TEST.C
#include "test.h"
#define FOO int x;

int main(){
FOO; /*comment */double y;
};
//END TEST.C

//BEGIN TEST.h
class Foo{
};
//END TEST.h

You would expect the line position of 'double' in test.C line 5 to
still be 5, but instead it is 6 because
   1. the line in test.C with just an "\n" in test.C does not count in
the line positioning (-1 line in position)
   2. there is no separation between the lines in test.h and test.C
(+2 lines in position)

thanks
Andreas
On 11/7/06, Hartmut Kaiser <hartmut.kaiser@gmail.com> wrote:
...
Andreas,
...
I need some advice regarding Wave. What I want to do is to
operate with Wave on a token stream and extract the token
stream representing macro calls after expansion. The twist is
that I want the token stream after expansion to have the
positions that another preprocessor would see on the already
expanded output from Wave. E.g:
#define MACRO_CALL int x;
int main(){
     MACRO
};
Exands into
#line 2
int main(){
     int x;
};
Where 'int x' should have a position of line 3 instead of
line 1 after expansion. I also want the column number to
represent what we see on line 3 instead of what we see on
line 1. Is this possible ?
Ok, I've added a new pp hook (what else? :-P) to Wave:
///////////////////////////////////////////////////////////////////////////
//
//  The function 'generated_token' will be called by the library whenever a
//  token is about to be returned from the library.
//
//  The parameter 'ctx' is a reference to the context object used for
//  instantiating the preprocessing iterators by the user.
//
//  The parameter 't' is the token about to be returned from the library.
//  This function may alter the token, but in this case it must be
//  implemented with a corresponding signature:
//
//      Token const&
//      generated_token(Context const& ctx, Token& t);
//
//  which makes it possible to modify the token in place.
//
//  The default behavior is to return the token passed as the parameter
//  without modification.
//
///////////////////////////////////////////////////////////////////////////
    template <typename Context, typename Token>
    Token const&
    generated_token(Context const& ctx, Token const& t)
    { return t; }
This should help solving your problem.
To show how this hook function may help you I added a new sample
'real_positions' to Wave demonstrating its use. Everything is in the Boost
CVS::HEAD.
HTH
Regards Hartmut
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Re: [Boost-users] [WAVE] position of tokens

Andreas Sæbjørnsen