Question

I want to know the exact contents of a program stack.

How is the branching operation done?

What is meant by memory dump while debugging a program using gdb?

Does it give the program stack?

TIA,
Praveen

Answer 1

The C language itself doesn’t mandate the use of a stack at all – it defines behaviour rather than implementation.

However, in the common case, the program stack is used to store several things:

• Objects declared with auto storage duration (ie. ordinary, non-static local variables);
• Function parameters;
• The return address (the location in the code where execution should resume after a return; or the end of the current function is reached);
• Memory allocated with the non-standard alloca() function;
• Temporary values required by the compiler, such as the saved contents of registers, housekeeping information for alloca(), the size of variable-length arrays and intermediate values used in calculations.

This is not an exhaustive list – other, more exotic things like Trampolines are also sometimes stored on the stack. In general, it is a temporary storage area for working items that will not be needed after the current function returns to its caller.

A “backtrace” in a debugger shows some (but not all) of the contents of the stack.