There are many constructs that now generate error messages from the CodeGear C++ compiler included with C++Builder 2007 and newer releases. The rules governing this behavior are described in section 8.5.3 of the 2003 C++ ANSI standard.  

The rules can be divided into the following categories (with the compiler switch that overrides this behavior):

• Binding a non-const lvalue to to non-const reference. (Use the compiler switch -Vbr to allow this.)
• Binding a temporary to a non-const reference. (Use the compiler switch -Vbr to allow this.)
• Binding of const or volatile objects to non-const or non-volatile methods repectively. (Use the compiler switch -Vbn to allow this.)

int takesLongRef(long& l);

  int takesUnsignedPtr(unsigned long* psize) {

     return takesLongRef((long)*psize);
  }

With C++Builder2007, the above code generates these errors:

Error E2357 test.cpp 3: Reference initialized with 'long', needs lvalue of type 'long' in function takesUnsignedPtr(unsigned long *)  

Error E2342 test.cpp 3: Type mismatch in parameter 'l' (wanted 'long &', got 'long') in function takesUnsignedPtr(unsigned long *)

To remedy this, you can cast psize before dereferencing, as in:

int takesLongRef(long& l);    
int takesUnsignedPtr(unsigned long* psize) {     return takesLongRef(*reinterpret_cast <long*>(psize));   }

Be aware of cases that involve temporaries in unobvious ways. For example, some binary operators imply a temporary:

enum { zero, one, two } num;     
num |= two; // Not allowed    
num = num | two; // OK 

Another case that involves temporaries in an unobvious way is the return value of a property. The following example illustrates code that compiled with previous versions of the compiler:

#include <vcl.h> 

class TTest {   
   WideString FData ;   
public:  
   __property WideString Data = {read = FData };   
};    

void Func(WideString& wref);    

void test() { 
   TTest t;  
   Func(t.Data);   
}

With C++Builder 2007, the above generates two errors:

Error E2357 test.cpp 14: Reference initialized with 'const WideString', needs lvalue of type 'WideString' in function test()   

Error E2342 test.cpp 14: Type mismatch in parameter 'wref' (wanted 'WideString &', got 'WideString') in function test()  

You can fix this by changing the reference to a const reference, as in:  

void Func(const WideString& wref);  

Here is an example of trying to bind a const object to a non-const method:

struct X {  
   void foo();   
};   
const X x;   
x.foo(); //error