How to find out who called a method?

Question

Example: When my method -fooBar gets called, I want it to log in the console which other method of which other class called it.

Right now, I only know how to log the method name of fooBar itself and it's class, with this:

_cmd

[self class]

Is this possible to figure out?

Answer 1

It's not possible in the general case without actually walking the stack. There's not even a guarantee that another object send the message that called the method. For example, it could be called from a block in a signal handler.

Answer 2

This information can be obtained using DTrace.

Answer 3

Make a macro that adds the __FUNCTION__ to the function name to the function call. This macro will then call your function with an extra parameter of a char* to the target function.

Answer 4

In fully optimized code, there is no 100% surefire way to determine the caller to a certain method. The compiler may employ a tail call optimization whereas the compiler effectively re-uses the caller's stack frame for the callee.

To see an example of this, set a breakpoint on any given method using gdb and look at the backtrace. Note that you don't see objc_msgSend() before every method call. That is because objc_msgSend() does a tail call to each method's implementation.

While you could compile your application non-optimized, you would need non-optimized versions of all of the system libraries to avoid just this one problem.

And this is just but one problem; in effect, you are asking "how do I re-invent CrashTracer or gdb?". A very hard problem upon which careers are made. Unless you want "debugging tools" to be your career, I would recommend against going down this road.

What question are you really trying to answer?

Answer 5

See backtrace(3).