Loki's STATIC_CAST macro

[LRS Kumar]

In Chapter 2 of MC++D, Andrei Alexandrescu introduces a macro called
STATIC_CAST. Here is the source related to it:


#ifndef STATIC_CHECK_INC_
#define STATIC_CHECK_INC_

namespace Loki
{

template<int> struct CompileTimeError;
template<> struct CompileTimeError<true> {};
}

#define STATIC_CHECK(expr, msg) \
{ Loki::CompileTimeError<((expr) != 0)> ERROR_##msg; (void)ERROR_##msg; }



#endif // STATIC_CHECK_INC_


I would be grateful if someone could explain to me the reason for the last line
of STATIC_CAST (the cast to void):
(void)ERROR_##msg;

STATIC_CAST seems to be doing its job even without this line. So why is it
needed?

Cheers,
LRS

 

[John Harrison]

In Chapter 2 of MC++D, Andrei Alexandrescu introduces a macro called
STATIC_CAST. Here is the source related to it:
STATIC_CHECK



#ifndef STATIC_CHECK_INC_
#define STATIC_CHECK_INC_

namespace Loki
{

template<int> struct CompileTimeError;
template<> struct CompileTimeError<true> {};
}

#define STATIC_CHECK(expr, msg) \
{ Loki::CompileTimeError<((expr) != 0)> ERROR_##msg; (void)ERROR_##msg; }



#endif // STATIC_CHECK_INC_


I would be grateful if someone could explain to me the reason for the last line
of STATIC_CAST (the cast to void):
(void)ERROR_##msg;

STATIC_CAST seems to be doing its job even without this line. So why is it
needed?

To me it looks like an attempt to avoid 'unused variable' type warning
messages when using STATIC_CHECK.

john