src/fallible.c


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#ifndef _POSIX_C_SOURCE
#define _POSIX_C_SOURCE 200809L
#endif

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

#ifdef TEST
#include <assert.h>
#endif

static const char *const default_db_name = "fallible-default";

bool fallible_should_fail(const char *const filename, int lineno) {
  static const char *db_name = NULL;
  if (!db_name && !(db_name = getenv("FALLIBLE_FILE"))) {
    db_name = default_db_name;
  }
  FILE *f = fopen(db_name, "a+");
  if (!f) {
    fprintf(stderr, "Failed to open '%s', exitting with error code 1.\n",
            db_name);
    exit(1);
  }

  int n = lineno;
  int digits = 0;
  while (n) {
    digits++;
    n /= 10;
  }

  char *current = malloc(strlen(filename) + 1 + digits + 1 + 1);
  sprintf(current, "%s:%d\n", filename, lineno);

  char *line = NULL;
  size_t len = 0;
  while (getline(&line, &len, f) != -1) {
    if (!strcmp(line, current)) {
      free(current);
      free(line);
      fclose(f);
      return false;
    }
  }

  fprintf(f, "%s", current);

  free(current);
  free(line);
  fclose(f);
  return true;
}