SUN 4.2 and 5.3 compiler.

Question

We are in process of upgrading our system from SUN 4.2 compiler to 5.3 and facing some problem.
Here is the very simple code for your reference.
// File test.cpp (start)
// ----------------part of code which I can not change (start) ------------------
template <class T>
class A
public:
typedef T* pointer;
typedef T& reference;
A(T& b) : a(b) {}
private:
reference a;
typedef A<void>::reference B;
//----------------part of code which I can not change (end) ------------------
void main()
int a = 10;
A<void> b(void);
// File test.cpp (end)
The same code I am able to compile with 4.2 with out any problem.
Here is the error message I am getting with 5.3 compiler.
.../apurohit<183> /opt/SUNWspro/bin/CC -V -compat=4 test.cpp
CC: Sun WorkShop 6 update 2 C++ 5.3 2001/05/15
ccfe: Sun WorkShop 6 update 2 C++ 5.3 2001/05/15
"trial.cpp", line 6: Error: Cannot declare a reference to void.
"trial.cpp", line 12: Where: While specializing "A<void>".
"trial.cpp", line 12: Where: Specialized in non-template code.
"trial.cpp", line 7: Error: Cannot declare a reference to void.
"trial.cpp", line 12: Where: While specializing "A<void>".
"trial.cpp", line 12: Where: Specialized in non-template code.
"trial.cpp", line 15: Warning (Anachronism): main() must have a return type of int.
2 Error(s) and 1 Warning(s) detected.
I know the reason for the error, but I want to know is there any solution for this problem?
Thanks in advance.

Answer 1

Template class A creates references to the type it is instantiated on. If you instantiate on type void, the code is invalid, because you cannot create a void&. (By definition, a reference must be initialized with an actual object, and there are no void objects.) C++ 4.2 was wrong to accept the invalid code.
Clearly, you should not be trying to create type A<void>. If you need A<void> for some reason, you can create a specialization on void that does not generate any references to void. For example, add this code prior to any mention of A<void>:
template<> class A<void> {
public:
typedef void* pointer;
private:
Ideally, this code should be added to the header that defines class template A, immediately after the primary template definition.
Type A<void>::pointer will be valid, but not A<void>::reference. And you cannot create an A<void> object that has a reference member. You could have a pointer member, but usage of A<void> would then not be the same as the usage of A<T> for other types T.
You say you cannot change the code. I'm afraid you will have to change the code, because I don't know of any compiler that will accept this invalid code.