C++ compile-time constant detection

Question

There\'re cases when a library source is available, and it has to support variable parameters in general, but in practice these parameters are commonly constants.

Th

Answer 1

is_const should be more reliable. On gcc-4.4 for example, the following:

int k=0;
printf("%d\n",is_const(k),is_const(k>0));

prints:

0,1

GCC is quite ambitious folding constant expressions which are not integral constant expressions by the words of the standard. A potentially better definition of is_const could be:

#define is_const(B)\
(sizeof(chkconst::chk2(0+!!(B))) != sizeof(chkconst::chk2(0+!(B))))

Aside from that, your technique is awesome, because I can finally write a SUPER_ASSERT macro which is checked during compilation if the assertion expression if compile-time and during runtime otherwise:

#define SUPER_ASSERT(X) {BOOST_STATIC_ASSERT(const_switch_uint(X,1));assert(X);}

I'll look into that const_switch_xxx() thing later. I have no idea how to implement another way, the deconstruct/reconstruct trick is brilliant.