[Swig-devel] [ swig-Bugs-3545277 ] Generated C code casts from void * to pointer-to-function

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Bugs item #3545277, was opened at 2012-07-17 23:26
Message generated for change (Settings changed) made by fedorabug
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Category: tcl
Group: None
Status: Open
Resolution: None
>Priority: 3
Private: No
Submitted By: fedorabug (fedorabug)
Assigned to: Nobody/Anonymous (nobody)
Summary: Generated C code casts from void * to pointer-to-function

Initial Comment:
The generated C code below casts from 'void *' to a function pointer which according to GCC is not legal C code. Commands used: 
swig -tcl baseFunc.i
gcc -x c -pedantic baseFunc_wrap.c -ltcl

/* baseFunc.i */
%module baseFunc

%{
#include "tclFunctions.c"
%}

%include "tclFunctions.h"

GCC:
baseFunc_wrap.c:2085:11: warning: ISO C forbids conversion of function pointer to object pointer type [-pedantic]

These are the statements and declarations involved, after running the preprocessor(clang -pedantic -E baseFunc_wrap.c):

typedef void *ClientData;
 
typedef int (*swig_wrapper)(ClientData, Tcl_Interp *, int, Tcl_Obj *const []);

    if (hashentry) {
        ClientData cd = ((hashentry)->clientData);
        swig_wrapper method_wrapper = (swig_wrapper)cd;  //Invalid cast
        oldarg = objv[1];
        objv[1] = inst->thisptr;
        ++(inst->thisptr)->refCount;
        rcode = (method_wrapper)(clientData,interp,objc,objv);
        objv[1] = oldarg;
        do { if (--(inst->thisptr)->refCount <= 0) TclFreeObj(inst->thisptr); } while(0);
        return rcode;
    }

Similar warnings are given when using c++.

swig -c++ -tcl baseFunc.i
clang++ -pedantic baseFunc_wrap.cxx -ltcl

baseFunc_wrap.cxx:2147:39: warning: cast between pointer-to-function and pointer-to-object is an extension
      [-pedantic]
          Tcl_SetHashValue(hashentry, (ClientData)meth->method);
          ~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/tcl.h:2353:69: note: expanded from macro 'Tcl_SetHashValue'
#define Tcl_SetHashValue(h, value) ((h)->clientData = (ClientData) (value))


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