Demo: Where Every Kind of Variable Lives

Initialised global, uninitialised global, constant, local array, alloca(), static local, malloc(), mmap(): each prints its address.

Run

make
./allocation-types
nm allocation-types | grep -E 'init_data|ro_data|local_scope_data|heap_data|mapped_data'
size allocation-types

Ask

• Three address ranges. Which variables share one, and why?
• nm prints addresses from the file, before it has run. Which of the printed addresses does it already know?
• local_scope_data is declared inside a function and lands next to the globals. What does static actually mean?
• .bss is 16 KB in memory. How many bytes of it are in the file?