assert caveat

[Till Straumann <strauman@slac.stanford.edu>]

Unless I miss something then it seems to me
that EPICS uses 'assert()' in the same way I often
do which AFAIK is incorrect:

assert( expression_with_side_effect );

because if the code is ever compiled with -DNDEBUG then
the side effect (eg locking a mutex in epicsMutexMustLock())
*goes*away*.

'assert' is a macro which evaluates to nothing if NDEBUG is defined.

The correct way of using assert would be:

 result = expression_with_side_effect;

 assert(result);

but it is inconvenient because the message printed by a failed
assertion would only say 'assertion of 'result' failed' and it would
not print the stringified expression.

My guess is that a lot of code would break if ever compiled
with -DNDEBUG...

Again:

#define NDEBUG
epicsMutexMustLock(my_lock);

is a no-op!

FWIW
-- Till


PS: It would be rather useful to have something like

#ifdef NDEBUG
#define usefulEpicsAssert(exp) (exp)
#else
#define usefulEpicsAssert(exp) ((exp) ? (void)(0) : assert(exp))
#endif