如何转换和打印结构成员的`void`指针数组？

huangapple
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英文:

How to covert and print the void pointer array of structure member?

问题

关于学习，我正在创建数据结构库，在那里我创建了堆栈的结构并添加了用于数组的void指针，当我尝试访问void指针数组的值时，会引发数据类型无效转换错误。有人能告诉我我哪里出错了？

  1. typedef struct
  2. {
  3.     size_t size;
  4.     size_t top;
  5.     void *st_base;
  6. } stack_t;
  8. dsa_err_t stack_init(stack_t *stack, uint32_t size)
  9. {
  10.     DSA_CHECK_ARG(stack);
  12.     stack->st_base = (int32_t *)calloc((size_t)size, sizeof(int32_t));
  13.     if (!(stack->st_base))
  14.     {
  15.         return DSA_NO_MEM;
  16.     }
  17.     stack->top = 0;
  18.     stack->size = size;
  19.     return DSA_OK;
  20. }
  22. dsa_err_t stack_push(stack_t *stack, int32_t item)
  23. {
  24.     DSA_CHECK_ARG(stack && stack->st_base);
  26.     if (stack->top >= (stack->size - 1))
  27.     {
  28.         return DSA_FAIL;
  29.     }
  31.     stack->st_base[(stack->top)++] = item; // 表达式必须是可修改的值错误
  32.     return DSA_OK;
  33. }
  35. dsa_err_t stack_pop(stack_t *stack, int32_t *item)
  36. {
  37.     DSA_CHECK_ARG(stack && stack->st_base);
  39.     if (stack_is_empty(stack) || stack->top > (stack->size - 1))
  40.     {
  41.         return DSA_FAIL;
  42.     }
  43.     *item = (int32_t)stack->st_base[stack->top - 1]; // 无效类型转换错误
  44.     stack->st_base[stack->top--] = 0;
  45.     return DSA_OK;
  46. }

注意：上述翻译只包括代码部分，不包括问题或其他内容。

英文:

As for learning I was creating the library of data structure there I create the structure of stack and added the void pointer use for array and when I m trying to access the value of void pointer array is throw the invalid conversion of data type error. Can anyone tell me where I m doing wrong?

  1. typedef struct
  2. {
  3.     size_t size;
  4.     size_t top;
  5.     void *st_base;
  6. } stack_t;
  8. dsa_err_t stack_init(stack_t *stack, uint32_t size)
  9. {
  10.     DSA_CHECK_ARG(stack);
  12.     stack->st_base = (int32_t *)calloc((size_t)size, sizeof(int32_t));
  13.     if (!(stack->st_base))
  14.     {
  15.         return DSA_NO_MEM;
  16.     }
  17.     stack->top = 0;
  18.     stack->size = size;
  19.     return DSA_OK;
  20. }
  21. dsa_err_t stack_push(stack_t *stack, int32_t item)
  22. {
  23. DSA_CHECK_ARG(stack && stack->st_base);
  25. if (stack->top >= (stack->size - 1))
  26. {
  27.     return DSA_FAIL;
  28. }
  30. stack->st_base[(stack->top)++] = item; ---> EXPRESSION MUST BE MODIFIABLE VALUE ERROR
  31. return DSA_OK;
  32. }
  34. dsa_err_t stack_pop(stack_t *stack, int32_t *item)
  35. {
  36. DSA_CHECK_ARG(stack && stack->st_base);
  38. if (stack_is_empty(stack) || stack->top > (stack->size - 1))
  39. {
  40.     return DSA_FAIL;
  41. }
  42. *item = (int32_t)stack->st_base[stack->top - 1]; ---> INVALID TYPE OF CONVERSION ERROR
  43. stack->st_base[stack->top--] = 0;
  44. return DSA_OK;
  45. }

答案1

得分: 3

void * 是一个不完整的类型，因此无法进行解引用（而数组索引是解引用的一种形式）。您需要首先将其转换为可用的指针类型。

  1. ((int32_t *)stack->st_base)[(stack->top)++] = item;
  2. ...
  3. *item = ((int32_t *)stack->st_base)[stack->top - 1];
英文:

A void * is an incomplete type and therefore can't be dereferenced (and array indexing is a form of dereferencing). You need to convert it to a usable pointer type first.

  1. ((int32_t *)stack->st_base)[(stack->top)++] = item;
  2. ...
  3. *item = ((int32_t *)stack->st_base)[stack->top - 1];

huangapple
  • 本文由 发表于 2023年3月10日 01:22:51
  • 转载请务必保留本文链接：https://go.coder-hub.com/75688022.html
  • c
  • data-structures
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