Avoiding unused variables warnings when using assert() in a Release build

Question

Sometimes a local variable is used for the sole purpose of checking it in an assert(), like so -

int Result = Func();
assert( Result == 1 );

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Answer 1

You could create another macro that allows you to avoid using a temporary variable:

#ifndef NDEBUG
#define Verify(x) assert(x)
#else
#define Verify(x) ((void)(x))
#endif

// asserts that Func()==1 in debug mode, or calls Func() and ignores return
// value in release mode (any braindead compiler can optimize away the comparison
// whose result isn't used, and the cast to void suppresses the warning)
Verify(Func() == 1);