How do I determine the memory layout of a structure?

Question

Suppose I have the following structure (in C):

struct my_struct {
  int foo;
  float bar;
  char *baz;
};

If I now have a variable, say

struct my_struct a_struct;

How can I find out how the fields of that structure are going to be laid out in memory? In other words, I need to know what the address of a_struct.foo, of a_struct.bar and a_struct.baz are going to be. And I cannot do that programatically, because I am actually cross-compiling to another platform.

CLARIFICATION

Thanks the answers so far, but I cannot do this programatically (i.e. with the offsetof macro, or with a small test program) because I am cross-compiling and I need to know how the fields are going to be aligned on the target platform. I know this is implementation-dependent, that's the whole point of my question. I am using GCC to compile, targeting an ARM architecture.

What I need in the end is to be able to dump the memory from the target platform and parse it with other tools, such as Python's struct library. But for that I need to know how the fields were laid out.

Answer 1

In general, this is implementation specific. It depends on things like the compiler, compiler settings, the platform you are compiling on, word-size, etc. Here's a previous SO thread on the topic: C struct memory layout?

If you are cross-compiling, I'd imagine the specific layout will be different depending on which platform you compile for. I'd consult references for your compiler and platform.