#pragma for defined class

#pragma for defined class

[Wesley Smith]

Hi,
I'm having some issues with a setup with alot of include files in a
C++ project.  In trying to debug it, I want to try and print out
whether or not classes have been defined in header files yet.

Here's the idea:


class Point
{

};


#ifndef Point
	#error Point
#endif


clearly this doesn't work, becaus ePoint is a class and not a #define.
 Is there a command that can pick up on whether a class has been
defined?

thanks,
wes

Re: #pragma for defined class

[John Love-Jensen]

Hi Wes,

Try this (careful on the line wrap of the #define)...

------------------------
template <bool x> struct STATIC_ASSERTION_FAILURE;
template <> struct STATIC_ASSERTION_FAILURE<true> { enum { value = 1 }; };
template <int x> struct static_assert_test { };
#define STATIC_ASSERT(x) \
typedef static_assert_test< sizeof(STATIC_ASSERTION_FAILURE< (bool)( x ) >)>
static_assert_typedef_ ## __LINE__

//class Foo; // Uncomment to see what happens.
//class Foo { }; // Uncomment to see what happens.
STATIC_ASSERT(sizeof(Foo) >= 0);
------------------------


Output if undeclared type Foo:
test.cpp:17: error: 'Foo' was not declared in this scope
test.cpp:17: error: template argument 1 is invalid

Output if forward declared (only) type Foo:
test.cpp:17: error: invalid application of 'sizeof' to incomplete type 'Foo'
test.cpp:17: error: invalid application of 'sizeof' to incomplete type
'STATIC_ASSERTION_FAILURE<false>'

Boost (www.boost.org) has the "boost/static_assert.hpp", which defines
BOOST_STATIC_ASSERT, and is more portable than the one I presented here.
Boost is free.  Boost is good.  Use Boost.

HTH,
--Eljay