Exceptions aren't usually really thrown "through" code; as the action implies, they are thrown "over" code.
As a forinstance; at least old-school Objective-C exceptions are usually implemented with setjmp and longjmp; essentially storing the addresses of code for later use.
It makes sense for C++ exceptions to be implemented with similar mechanisms; and as such; the type of code the exception is thrown "through", or more accurately, "over" matters little, if at all. One could even imagine a setting where an Objective-C exception is thrown over a C++ catch, or vice versa.
Edit: As Bo Persson mentiones; this is not to say that a C++ exception interrupting C code wouldn't cause havoc and leaks; but exceptions being thrown is usually a Bad Thing™ all round; so it's not likely to matter much.
PS: Kudos on actually asking a question where using both C and C++ tags is relevant. ;)
