Hello Andrzej, I understand your suggestion but not fully removing the contract macros has the following key disadvantages: 1) It still increases compile-time. During development, I find it useful to be able to *completely* strip the contracts away, including from compilation -- it saves me from waiting extra time to compile contract code that I am not executing yet. 2) Inv, pre, and post conditions are programmed by the library in private member functions (the assertions cannot appear in the body because the body might be defined in .cpp separated from the contract declaration). I think compilation of these extra member functions will still increase the object size (even if if these functions are private, called by no one, and they only contain statements like `sizeof(expression)` that have no effect) -- I have not verified this. Plus, you can always make sure the contracts are syntactically correct by deliberately compiling with all contract on every so often. Therefore, I will keep the current design that expands the contract macros to nothing when contract compilation is off. I will make this reasoning clear in the documentation. On Sun, Feb 28, 2010 at 4:57 PM, Andrzej Krzemienski <akrzemi1@gmail.com> wrote:
this is how C-style asserts work, but one of the advantage of asserts over comments, as it is often advertised, is that the predicates are checked for syntactic and (to some extent) semantic correctness. But this is not the case if we disable the assertion macros.
The Contract Programming benefit usually advertised as "trustworthy documentation" (see [Meyer1997]) is gained only when contracts are compiled and *executed* during testing so they are checked not just syntactically but also semantically by the test suite.
be possible if the macro
CONTRACT_ASSERT_BLOCK_INVARIANT( expression );
were replaced with something like:
... sizeof( expression ) ...
then, the expression is not evaluated, but required to be correct. If the value of sizeof is not used it should be eliminated by the compiler. Obviously, the same would be applicable for all the other
BTW, [Stroustrup1997] suggests to use `Assert(!CONTRACT_CHECK_BLOCK_INVARIANT || expression)` to implement a similar functionality.