Visualize chunk list of malloc

test.cpp

#include <cstdio>
#include <cstdlib>
#include <omp.h>
const int N = 128;
int
main(int argc, char **argv) {
  char *buf[N];
  size_t size = 128;
  #pragma omp parallel for
  for (int i = 0; i < N; i++) {
    buf[i] = (char*)malloc(size);
  }
  for (int i = 0; i < N; i++) {
    for (int j = 0; j < size; j++) {
      buf[i][j] = 0;
    }
  }
  for (int i = 0; i < N; i++) {
    free(buf[i]);
  }
  printf("digraph test_%d\n {\n", size);
  for (int i = 0; i < N; i++) {
    size_t *p = (size_t*)(buf[i]);
    size_t prev_size = *(p - 2);
    if (prev_size != 0)continue;
    size_t *ct = p - 2;
    size_t fd = *p;
    printf("\"%lx\"->\"%lx\"\n", ct, fd);
  }
  printf("}\n");
}

test.png

$ g++ -fopenmp test.cpp
$ OMP_NUM_THREADS=24 ./a.out
digraph test_128
 {
"608160"->"2aaaabc23ed8"
"606c90"->"608160"
"606c00"->"2aaaabc23ed8"
"609240"->"608a60"
"609e10"->"609240"
"2aaab0000b70"->"2aaab0000078"
"608a60"->"608160"
"6097e0"->"608a60"
"60a710"->"609240"
"608f70"->"608a60"
"607620"->"608a60"
"608790"->"2aaaabc23ed8"
"2aaab00008a0"->"2aaab0000078"
"607e90"->"606810"
"606810"->"2aaaabc23ed8"
"6069c0"->"2aaaabc23ed8"
}