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？
typedef struct
{
size_t size;
size_t top;
void *st_base;
} stack_t;
dsa_err_t stack_init(stack_t *stack, uint32_t size)
{
DSA_CHECK_ARG(stack);
stack->st_base = (int32_t *)calloc((size_t)size, sizeof(int32_t));
if (!(stack->st_base))
{
return DSA_NO_MEM;
}
stack->top = 0;
stack->size = size;
return DSA_OK;
}
dsa_err_t stack_push(stack_t *stack, int32_t item)
{
DSA_CHECK_ARG(stack && stack->st_base);
if (stack->top >= (stack->size - 1))
{
return DSA_FAIL;
}
stack->st_base[(stack->top)++] = item; // 表达式必须是可修改的值错误
return DSA_OK;
}
dsa_err_t stack_pop(stack_t *stack, int32_t *item)
{
DSA_CHECK_ARG(stack && stack->st_base);
if (stack_is_empty(stack) || stack->top > (stack->size - 1))
{
return DSA_FAIL;
}
*item = (int32_t)stack->st_base[stack->top - 1]; // 无效类型转换错误
stack->st_base[stack->top--] = 0;
return DSA_OK;
}
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?
typedef struct
{
size_t size;
size_t top;
void *st_base;
} stack_t;
dsa_err_t stack_init(stack_t *stack, uint32_t size)
{
DSA_CHECK_ARG(stack);
stack->st_base = (int32_t *)calloc((size_t)size, sizeof(int32_t));
if (!(stack->st_base))
{
return DSA_NO_MEM;
}
stack->top = 0;
stack->size = size;
return DSA_OK;
}
dsa_err_t stack_push(stack_t *stack, int32_t item)
{
DSA_CHECK_ARG(stack && stack->st_base);
if (stack->top >= (stack->size - 1))
{
return DSA_FAIL;
}
stack->st_base[(stack->top)++] = item; ---> EXPRESSION MUST BE MODIFIABLE VALUE ERROR
return DSA_OK;
}
dsa_err_t stack_pop(stack_t *stack, int32_t *item)
{
DSA_CHECK_ARG(stack && stack->st_base);
if (stack_is_empty(stack) || stack->top > (stack->size - 1))
{
return DSA_FAIL;
}
*item = (int32_t)stack->st_base[stack->top - 1]; ---> INVALID TYPE OF CONVERSION ERROR
stack->st_base[stack->top--] = 0;
return DSA_OK;
}
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。
((int32_t *)stack->st_base)[(stack->top)++] = item;
...
*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.
((int32_t *)stack->st_base)[(stack->top)++] = item;
...
*item = ((int32_t *)stack->st_base)[stack->top - 1];
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