sbrk
是在阅读 wikipedia C dynamic memory allocation # Heap-based 时，发现了其中提及了 sbrk。
man7 brk(2) — Linux manual page
#include <unistd.h>
int brk(void *addr);
void *sbrk(intptr_t increment);
brk() and sbrk() change the location of the program break, which defines the end of the process's data segment (i.e., the program break is the first location after the end of the uninitialized data segment). Increasing the program break has the effect of allocating memory to the process; decreasing the break deallocates memory.
NOTE: 关于 program break，参见
Program-break章节。上述 uninitialized data segment，其实就是bss。