in reply to SWIG and conflicting definitions

Hello jdv!

Lets see if I got this correctly:

  1. XSUB.h is included in line 745 of pwiz_swigbindings_wrap.cxx, defining typedef struct cv CV and macro XS.
  2. cv.hpp is included in line 1862 of pwiz_swigbindings_wrap.cxx, defining a different struct CV.
  3. the XS macro from Perl is used first in line 2149 of pwiz_swigbindings_wrap.cxx

It is ugly, but the preprocessor can help to move the conflicting identifiers around. To do so I would manually modify the file pwiz_swigbindings_wrap.cxx and insert this line before
#define CV __perl_CV
and these ones after
#undef XSPROTO
#define XSPROTO(name) void name(pTHX_ __perl_CV* cv)
#undef CV
line 745.

I checked this roughly with the following C code: 
#define CV __perl_CV
/* beginning of include XSUB.h */
struct cv {
        int i;
};
typedef struct cv CV;
#define XSPROTO(name) CV name
/* end of include XSUB.h */
#undef XSPROTO
#define XSPROTO(name) __perl_CV name
#undef CV

struct CV {
        char c;
};

XSPROTO(x);

int main()
{
        struct CV y;
        x.i = 0;
        y.c = '!';
        return 0;
}

[download]

Replies are listed 'Best First'.
Re^2: SWIG and conflicting definitions
by jdv (Sexton) on Jan 07, 2016 at 19:17 UTC

    Thanks for the reply. This is all black magic to me (plus I think some newlines got lost in the code in your first paragraph) so I'm not sure if I got it right. Here is what I tried around the section you suggested:

    #include "EXTERN.h"
#include "perl.h"
#define CV __perl_CV
#include "XSUB.h"
#undef XSPROTO
#define XSPROTO(name) void name(pTHX_ __perl_CV* cv)
#undef CV

    [download]

    That's just copying what you wrote and guessing at the newlines, so I'm not sure if the syntax is correct. If I try to compile this, the STDERR is down to ~ 1500 lines with a lot of messages like this:

    pwiz_swigbindings_wrap.cxx:748:39: error: ‘__perl_CV’ has not been dec
+lared
 #define XSPROTO(name) void name(pTHX_ __perl_CV* cv)

    [download]
[reply]
[d/l]
[select]
      My error, sorry. I should have said to put the line

      #define CV __perl_CV

      before this one

      #include "perl.h"

      otherwise it looks ok.

      Update: some explanations added

      What I intend to do, is this:

      1. for the processing of perl.h, XSUB.h and the included header files therein, substitute the offending identifier CV by __perl_CV. This is done by the preprocessor directive #define CV __perl_CV
      2. Afterwards redeclare the macro XSPROTO, which was using CV also. Unfortunately the above substitution affects only C code, but not subsequent preprocessor directives, so we need to adjust this macro definition.
        This is done by first deleting the old macro definition (#undef XSPROTO), and then by defining it again, but this time with __perl_CV instead of CV.
      3. Finally delete the substitution for identifier CV (#undef CV, so that the following code can use it exclusively.
      4. This in total should remove the conflict between the two different definitions of CV by using __perl_CV for the first one instead.

      If you are curious, you can look at the difference of the preprocessed outputs with and without the modification (gcc -E -dDfile should produce them).

[reply]
[d/l]
[select]

        Thanks - that is progress. After making that change, STDERR is down to 21 lines. This is the full output:

        Read more... (2 kB)

        Here is the context refered to in the first line:

        Read more... (515 Bytes)

        I really appreciate the help so far. I'd love to get this working but troubleshooting at this level is beyond me.

[reply]
[d/l]
[select]

In Section Seekers of Perl Wisdom