C++ 'extern inline' magic possible?

[Kevin P. Fleming]

On 03/01/2011 04:52 PM, Jonathan Wakely wrote:
> On 1 March 2011 12:14, Kevin P. Fleming wrote:
>>
>> Yes, that was what my original post requested, but I now understand that any
>> solution that offered that would be non-compliant with the C++ standard. I
>> believe this code base is only using this technique to shave some compile
>> time for TUs that don't actually need the class definitions (they only
>> receive and send around pointers to the classes), but it's a cause of lower
>> performance and so I'll have to figure out whether removing the 'forward
>> declaration only' mechanism will be worth the effort.
>
> There is another option, which I'm loathe to mention ...

<snip macro example which makes everyone shudder <G>>

Yes, I considered that. I did arrive at a potential solution, although I 
can't use it in this particular code base because of other 
complications, but...

== test.h ==
class Foo;

void opaqueBar(Foo*);

template <typename T>
void Bar(T* obj)
{
	opaqueBar(obj);
}

== test1.h ==
#include "test.h"

static void test1(Foo* obj)
{
	Bar(obj);
}

== test2.h ==
#include "test.h"

class Foo
{
public:
	void realBar();
};

template <>
inline void Bar<Foo>(Foo* obj)
{
	obj->realBar();
}

static void test2(Foo* obj)
{
	Bar(obj);
}

I think this still might be an ODR violation though, since there will 
end up being two definitions of Bar() for Foo.

-- 
Kevin P. Fleming
Digium, Inc. | Director of Software Technologies
445 Jan Davis Drive NW - Huntsville, AL 35806 - USA
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