Injecting a function into code generation

Injecting a function into code generation

[Sebastian Redl]

Hi,

I'm currently trying to implement the C++09 exception propagation 
proposal (N2179). See the thread at
http://gcc.gnu.org/ml/libstdc++/2008-05/msg00079.html
in the libstdc++ list for details.

As I say in my first follow-up, I need a copy constructor for any type 
with a consistent signature. In other words, I need a function like this:

template <typename T>
void copy_constructor(T *dest, const T *src)
{
  new (dest) T(*src);
}

Then I can generate the equivalent of

void (*copy)(void*, const void*) = reinterpret_cast<void (*)(void*, 
const void*)>(
  &copy_constructor<actual_type>);

to get a function that can copy-construct an arbitrary type (given that 
I know the type, which I do).

The problem is that, since this stuff is done in the tree building in 
except.c, I can't rely on any header having been included and defining 
such a function.

How can I generate this function in code? I need one instantiation per 
type that is thrown, and it would be nice to avoid defining the function 
anew for every throw expression. I tried finding an existing case of 
this in the source, but I can't think of any place where such a thing 
would be done, except perhaps generation of an implicit special member. 
But I can't find those.

Sebastian