bisect_malloc.c

// Copyright (c) 2021 Sebastian Pipping <sebastian@pipping.org>
// Licensed under the Apache license version 2.0
//
// Compile and run with:
// # gcc -std=gnu99 -Wall -Wextra -pedantic bisect_malloc.c && ./a.out

#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>

int main() {
  const struct timespec sleepFor = {.tv_sec = 0, .tv_nsec = 125 * 1000 * 1000};

  size_t left = 0;
  size_t right = (size_t)-1;
  bool firstRound = true;

  for (;;) {
    const size_t candidate = firstRound ? right : (left / 2 + right / 2);
    if (candidate == left) {
      break;
    }

    printf("Trying to allocate %21zu bytes... ", candidate);
    void *const malloced = malloc(candidate);
    if (malloced) {
      printf("PASS\n");
      free(malloced);
      left = candidate;
    } else {
      printf("     FAIL\n");
      if (!firstRound) {
        right = candidate;
      }
    }

    nanosleep(&sleepFor, NULL);
    firstRound = false;
  }

  printf("\nDone, biggest success was %zu bytes.\n", left);
  return 0;
}