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我正在为将给定字符串附加到动态字符数组末尾的函数编写 ACSL 规范。

这是我到目前为止所拥有的：

#include <stddef.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>

#ifndef SIZE_MAX
#define SIZE_MAX ((size_t)-1)
#endif

#undef MAX
#define MAX(a, b) ((a) > (b) ? (a) : (b))

struct st_char_vector {
  char *buf;
  size_t capacity;
  size_t length;
};

/*@ predicate valid_char_vector(struct st_char_vector *vec) =
  @   \valid_read(vec) &&
  @   vec->capacity > 0 &&
  @   \valid(vec->buf + (0..vec->capacity - 1)) &&
  @   vec->length <= vec->capacity;
  @*/


/*@ requires valid_char_vector(vec);
  @ requires new_capacity >= vec->capacity;
  @ ensures valid_char_vector(vec);
  @ ensures \old(vec->length) == vec->length;
  @ ensures memcmp{Pre,Post}(vec->buf, vec->buf, vec->length) == 0;
  @ behavior err:
  @   ensures !\result;
  @   ensures \old(vec->buf) == vec->buf;
  @   ensures \old(vec->capacity) == vec->capacity;
  @ behavior ok:
  @   ensures \result;
  @   ensures vec->capacity >= new_capacity;
  @ complete behaviors;
  @ disjoint behaviors;
  @*/
static int char_vector_reallocate(struct st_char_vector *vec, size_t new_capacity);

/*@ requires valid_char_vector(vec);
  @ requires \valid_read(str + (0..str_length - 1));
  @ requires string_separated_from_extra_capacity:
  @   \separated(str + (0..str_length - 1), vec->buf + (vec->length..vec->capacity - 1));
  @ ensures valid_char_vector(vec);
  @ ensures old_content_unchanged: memcmp{Pre,Post}(vec->buf, vec->buf, \old(vec->length)) == 0;
  @ ensures \forall integer i; 0 <= i && i < \old(vec->length) ==> \old(vec->buf[i]) == vec->buf[i];
  @ behavior err:
  @   ensures !\result;
  @   ensures buf_unchanged: \old(vec->buf) == vec->buf;
  @   ensures capacity_unchanged: \old(vec->capacity) == vec->capacity;
  @   ensures length_unchanged: \old(vec->length) == vec->length;
  @ behavior ok:
  @   ensures \result;
  @   ensures str_length_added_to_length: vec->length == \old(vec->length) + str_length;
  @   ensures string_appended: memcmp{Post,Post}(vec->buf + \at(vec->length, Pre), str, str_length) == 0;
  @ complete behaviors;
  @ disjoint behaviors;
  @*/
int char_vector_append(struct st_char_vector *vec, const char *str, size_t str_length) {
  if (SIZE_MAX - str_length < vec->capacity) {
    return 0;
  }

  if (vec->capacity < (vec->length + str_length)) {
    if (!char_vector_reallocate(vec, vec->capacity + str_length)) {
      //@ assert \at(vec->length, Pre) == \at(vec->length, Here);
      return 0;
    }
  }

  memcpy(vec->buf + vec->length, str, str_length);
  vec->length += str_length;

  return 1;
}

因为还不支持动态内存分配的验证，所以我添加了一个占位符函数char_vector_reallocate()和 ACSL 规范，但没有展示实现。

使用 Frama-C Sodium-20150201 和 WP 插件，我无法验证 6 个属性：

  • typed_char_vector_append_disjoint_ok_err
  • typed_char_vector_append_err_post
  • typed_char_vector_append_err_post_length_unchanged
  • typed_char_vector_append_ok_post
  • typed_char_vector_append_ok_post_str_length_added_to_length
  • typed_char_vector_append_ok_post_string_appended

我没想到验证前 5 个属性会遇到任何困难。

如何修复 ACSL 以便char_vector_append()验证？

（作为旁注，是否有我可以参考的动态数组的示例 ACSL 规范？）

4

1 回答 1

2

您缺少assumes允许 WP 区分您ok和err案例的条款。一个很好的证据是您无法证明disjoint合同条款。基本上，如果

  • 缓冲区大小和字符串的总和太大，或者
  • 缓冲区太小而无法容纳字符串，并且
  • 内存不足

为了对第三点进行建模，我建议使用 ghost 变量来指示是否有足够的空闲内存来扩展向量。在您的情况下，由于只有一个分配，因此一个简单的布尔标志就可以解决问题，例如//@ ghost int mem_full.

当然，您需要相应地调整 of 的规范char_vector_reallocate：它应该assigns mem_full和它behavior的 s 应该有assumes基于 的初始值的子句mem_full。

最后，在 of和 inmemcmp子句中的ensures第一个参数存在问题：参数本身应该在-state 中进行评估。否则，您是说-state 中（在-state 中）指向的任何内容与-state 中（再次在-state 中）指向的内容相等。也就是说，参数的评估发生在当前状态，不管参数中给出的标签。char_vector_reallocateold_content_unchangedPrevec->bufPostPrevec->bufPostPostmemcmp

以下是 Alt-Ergo 证明一切的版本

#include "stdlib.h"
#include "string.h"

#ifndef SIZE_MAX
#define SIZE_MAX ((size_t)-1)
#endif

#undef MAX
#define MAX(a, b) ((a) > (b) ? (a) : (b))

struct st_char_vector {
  char *buf;
  size_t capacity;
  size_t length;
};

/*@ predicate valid_char_vector(struct st_char_vector *vec) =
  @   \valid_read(vec) &&
  @   vec->capacity > 0 &&
  @   \valid(vec->buf + (0..vec->capacity - 1)) &&
  @   vec->length <= vec->capacity;
  @*/

//@ ghost extern int mem_full;

/*@ requires valid_char_vector(vec);
  @ requires new_capacity >= vec->capacity;
  @ assigns mem_full;
  @ ensures valid_char_vector(vec);
  @ ensures \old(vec->length) == vec->length;
  @ ensures valid_char_vector(vec);
  @ ensures memcmp{Pre,Post}(\at(vec->buf,Pre), vec->buf, vec->length) == 0;
  @ behavior err:
      assumes mem_full;
  @   ensures !\result;
  @   ensures \old(vec->buf) == vec->buf;
  @   ensures \old(vec->capacity) == vec->capacity;
  @ behavior ok:
      assumes !mem_full;
  @   ensures \result;
  @   ensures vec->capacity >= new_capacity;
  @ complete behaviors;
  @ disjoint behaviors;
  @*/
static int char_vector_reallocate(struct st_char_vector *vec, size_t new_capacity);

/*@ requires valid_char_vector(vec);
  @ requires \valid_read(str + (0..str_length - 1));
  @ requires string_separated_from_extra_capacity:
  @   \separated(str + (0..str_length - 1), vec->buf + (vec->length..vec->capacity - 1));
  @ ensures valid_char_vector(vec);
  @ ensures old_content_unchanged: memcmp{Pre,Post}(\at(vec->buf,Pre), vec->buf, \old(vec->length)) == 0;
  @ ensures \forall integer i; 0 <= i && i < \old(vec->length) ==> \old(vec->buf[i]) == vec->buf[i];
  @ behavior err:
      assumes vec->capacity+str_length>SIZE_MAX || 
      (vec->length+str_length>vec->capacity && mem_full);
  @   ensures !\result;
  @   ensures buf_unchanged: \old(vec->buf) == vec->buf;
  @   ensures capacity_unchanged: \old(vec->capacity) == vec->capacity;
  @   ensures length_unchanged: \old(vec->length) == vec->length;
  @ behavior ok:
      assumes vec->capacity+str_length<=SIZE_MAX && 
      (vec->length+str_length<=vec->capacity || !mem_full);
  @   ensures \result;
  @   ensures str_length_added_to_length: vec->length == \old(vec->length) + str_length;
  @   ensures string_appended: memcmp{Post,Post}(vec->buf + \at(vec->length, Pre), str, str_length) == 0;
  @ complete behaviors;
  @ disjoint behaviors;
  @*/
int char_vector_append(struct st_char_vector *vec, const char *str, size_t str_length) {
  if (SIZE_MAX - str_length < vec->capacity) {
    return 0;
  }

  if (vec->capacity < (vec->length + str_length)) {
    if (!char_vector_reallocate(vec, vec->capacity + str_length)) {
      return 0;
    }
  }
   memcpy(vec->buf + vec->length, str, str_length);
  vec->length += str_length;

  return 1;
}
于 2015-11-13T18:45:56.953 回答