Re: Using STL(map) inside of C data structure. How?

Hi,

In order to work, you would have to replace the malloc call with
new[]. That way, the map constructor will be called.

If your question was in the context of mixing C with C++ code, the
answer is more complex.

1- You must write the main function in a C++ TU to make sure that C++
runtime environment is setup correctly.

2- Create a TU presenting a C interface for manipulating sType:

sType.h

#ifdef __cplusplus
extern "C"
{
#endif

typedef struct {
   void *m; /* Must be type less as you cannot include a C++ template
class declaration in C modules
} sType;

/* C style constructor/destructor */
sType *create_sType();
destroy_sType(sType *);

use_sType(sType *);

#ifdef __cplusplus
}
#endif

sType.cpp

inline std::map<const char*, int> *getMap(sType *s)
{
     return static_cast<std::map<const char*, int> *>(s->m);
}

// You must wrap your C functions entry points to be sure that
// C++ exceptions do not cross into C modules.

sType *create_sType()
{
     try
     {
         sType *res = new sType;
         res->m = std::map<const char*, int>;
         return res;
     }
     catch(...)
     {
     }
     return NULL;
}

destroy_sType(sType *s)
{
     delete getMap(s);
     delete s;
}

/*
  * For every methods that need to use the map, use the inline function
getMap() to retrieve
  * the map from the sType POD.
  */
use_sType(sType *s)
{
}

Greetings,
Olivier Langlois
http://www.olivierlanglois.net

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