On Wed, Jan 22, 2014 at 1:21 PM, Thorsten Ottosen < thorsten.ottosen@dezide.com> wrote:
On 22-01-2014 13:11, Mathias Gaunard wrote:
On 22/01/14 11:52, Alexander Lamaison wrote:
BOOST_TEST(a <operator> b), however, cleverly parses a, b and <operator>
from the macro and does something like
bool x = (a <operator> b) BOOST_CHECK_MESSAGE_IMPL(x, "a must be <operator> to b", a, b);
What sort of magic allows to parse a <operator> b, and how reliable is it in the real world?
Completely reliable. You just bind the first object to some wrapper class object which provide the overloaded operators (via delegation).
This seems to rely on an op->* operator, which has lower precedence than unary op* (dereference), and the macro INTERNAL_CATCH_TEST uses un-parenthesized Catch::ExpressionDecomposer()->*expr, so won't this break if I do MACRO(*lhs_ptr == *rhs_ptr)? I suppose MACRO((*lhs_ptr) == *rhs_ptr) might fix it, but the compile error for the obvious code might come as a surprise to many, no? I'm no C++ expert, so perhaps the above is nonsense, but I'd be interested in more details as to how this technique can be completely reliable, as stated by Thorsten. Thanks, --DD