cast question

[Patrick Guio]

Dear all,


I have a C function that returns a void pointer (void *).
This object pointer is actually a pointer to function.
I have the following declarations:

void *pobj;
double (*func)(double);

I am trying to convert pobj into func with a reinterpret_cast

fun = reinterpret_cast<double (*)(double)>(pobj);

but I get a compiler error that says that ISO C++ forbids casting between
pointer-to-function and pointer-to-object.

Any idea how to force such cast ?

Sincerely,

Patrick

 

[Ioannis Vranos]

I have a C function that returns a void pointer (void *).
This object pointer is actually a pointer to function.
I have the following declarations:

void *pobj;
double (*func)(double);

I am trying to convert pobj into func with a reinterpret_cast

fun = reinterpret_cast<double (*)(double)>(pobj);

but I get a compiler error that says that ISO C++ forbids casting
between pointer-to-function and pointer-to-object.

Any idea how to force such cast ?

By using a C style cast:


func=(double (*) (double) ) (pobj);

 

[Siemel Naran]

I am trying to convert pobj into func with a reinterpret_cast

fun = reinterpret_cast<double (*)(double)>(pobj);

but I get a compiler error that says that ISO C++ forbids casting between
pointer-to-function and pointer-to-object.

My compiler (Borland 6) allows the cast, though another (g++ 2.95) forbids
it. I guess g++ is right.

However, you can reinterpret_cast from one function type to another, which
might be be of use.

 

[Serock]

You can convert pobj into func as below:

void *pobj;
double (*func)(double);
*((void**)&func) = pobj;

under g++ 2.4.2

 

[Serock]

You can try to convert pobj into func as below:

void *pobj;
double (*func)(double);
*((void**)&func) = pobj;

can pass under g++ 3.4.2

 

[Jack Klein]

Dear all,


I have a C function that returns a void pointer (void *).
This object pointer is actually a pointer to function.
I have the following declarations:

void *pobj;
double (*func)(double);

I am trying to convert pobj into func with a reinterpret_cast

fun = reinterpret_cast<double (*)(double)>(pobj);

but I get a compiler error that says that ISO C++ forbids casting between
pointer-to-function and pointer-to-object.

Any idea how to force such cast ?

Sincerely,

Patrick

There is no defined conversion between any pointer to object type,
including pointer to void, and any pointer to function type. A
C-style cast is accepted, but the result is completely undefined.

Complain to the source of the function, it is, has been, and always
will be bad code.