> Though I believe that a degree of indirection is preserved on AMD64 to enable symbol interposition?
You really don't want symbol interdiction. You don't use it most of the time, and the rest of the time, you're just changing a call that looks like:
foo(1, 2);
to
(*g_foo)(1, 2);
Which do you think is faster? There's a reason everything on Android compiles with -Bsymbolic (which kills interdiction for calls between functions in the same module). You really should be compiling all your code with -Bsymbolic -fvisibility=hidden; explicitly export the symbols you want other modules to call.
The first is faster, of course. Whether or not I want the second depends entirely on what I'm doing :) It certainly shouldn't be the default - it isn't very useful during normal work - but I've been glad to have it before.
I wouldn't recommend -Bsymbolic by default unless you know it's safe for your environment, though. There is software that uses symbol interposition to 'productive' ends in production (not much of it, thank heavens). Mobile platforms are something of a special case.
C++ exceptions exempted (see -Bsymbolic-functions), anything broken with -Bsymbolic is inherently broken and ought to be fixed. The same goes for symbol interposition. There are ways of providing extension points that are saner than allowing any shared library that happens to be loaded into your process the ability to override one of your functions.
Ought to be fixed doesn't mean will be fixed, unfortunately. Especially when the people doing the fixing wouldn't be the developers. Fortunately there aren't too many applications that rely on interposition to function.
As for myself: I've only ever used symbol interposition for debugging, instrumentation, etc . . . for which it was quite useful (as I've said). I pay attention to what my libraries export, so accidental interposition has never been a problem for me. (Making that easier by default is something that I would support.) I'll happily discuss the matter further, but I'm not interested in arguing it.
