c - 从 C 中的数组堆栈中弹出 - 将 NULL 分配给 int *

Question

考虑以下数组堆栈的定义:

typedef struct larray{
    int values[BSize];
    struct larray *prox;
}*LArrays;

typedef struct stack{
    int sp; //number of occupied positions in stack's top array
    LArrays s; //stack top
}Stack;

我写了这个 pop 函数:

int pop(Stack *st, int *t){
    if (st->sp == 0) return -1;

    if (st->sp == 1){
        LArrays newTop = st->s->prox;
        free(st->s);
        st->s = NULL;
        st->s = newTop;
        st->sp = BSize;
        return 0;
    }

    LArrays l = st->s;
    int *remover = l->values + (--st->sp);  
    *t = *remover;
    *remover = NULL;

    return 0;
}

它有效。但是编译时，gcc 会产生以下警告:

warning: assignment makes integer from pointer without a cast [-Wint-conversion]

     *remover = NULL;

将 NULL 赋给 int * 是错误的吗？

[更改为删除器后的结果 = NULL]

主要:

for (; i < 150; i++)
        push(stack,i);
    i = 0;

    printStack(stack);

    for (; i < 70; i++)
        pop(stack,&r);

    printStack(stack);

with *remover = NULL (produces desired output!)

//stack after push

100|101|102|103|104|105|106|107|108|109|110|111|112|113|114|115|116|117|118|119|120|121|122|123|124|125|126|127|128|129|130|131|132|133|134|135|136|137|138|139|140|141|142|143|144|145|146|147|148|149|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|]

---------------------------------------------------------
0|1|2|3|4|5|6|7|8|9|10|11|12|13|14|15|16|17|18|19|20|21|22|23|24|25|26|27|28|29|30|31|32|33|34|35|36|37|38|39|40|41|42|43|44|45|46|47|48|49|50|51|52|53|54|55|56|57|58|59|60|61|62|63|64|65|66|67|68|69|70|71|72|73|74|75|76|77|78|79|80|81|82|83|84|85|86|87|88|89|90|91|92|93|94|95|96|97|98|99|]

//stack after pop
0|1|2|3|4|5|6|7|8|9|10|11|12|13|14|15|16|17|18|19|20|21|22|23|24|25|26|27|28|29|30|31|32|33|34|35|36|37|38|39|40|41|42|43|44|45|46|47|48|49|50|51|52|53|54|55|56|57|58|59|60|61|62|63|64|65|66|67|68|69|70|71|72|73|74|75|76|77|78|79|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|]

with remover = NULL (does not produce the desired output!)

//stack after push

100|101|102|103|104|105|106|107|108|109|110|111|112|113|114|115|116|117|118|119|120|121|122|123|124|125|126|127|128|129|130|131|132|133|134|135|136|137|138|139|140|141|142|143|144|145|146|147|148|149|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|]

---------------------------------------------------------
0|1|2|3|4|5|6|7|8|9|10|11|12|13|14|15|16|17|18|19|20|21|22|23|24|25|26|27|28|29|30|31|32|33|34|35|36|37|38|39|40|41|42|43|44|45|46|47|48|49|50|51|52|53|54|55|56|57|58|59|60|61|62|63|64|65|66|67|68|69|70|71|72|73|74|75|76|77|78|79|80|81|82|83|84|85|86|87|88|89|90|91|92|93|94|95|96|97|98|99|]


//stack after pop
0|1|2|3|4|5|6|7|8|9|10|11|12|13|14|15|16|17|18|19|20|21|22|23|24|25|26|27|28|29|30|31|32|33|34|35|36|37|38|39|40|41|42|43|44|45|46|47|48|49|50|51|52|53|54|55|56|57|58|59|60|61|62|63|64|65|66|67|68|69|70|71|72|73|74|75|76|77|78|79|80|81|82|83|84|85|86|87|88|89|90|91|92|93|94|95|96|97|98|99|]

打印功能:

void printArray(int *v, int N){
    int *p = v;
    int i = 0;
    for(; i < N; i++)
        printf("%d|",*p++);
    printf("]\n\n");
}

void printStack(Stack *stack){
    LArrays p = stack->s;
    printf("Free Space on Stack's head: %d\n",BSize - stack->sp);
    printf("\nStack:\n\n");
    while(p->prox != NULL){
        printArray(p->valores,BSize);
        printf("------------------------------------------------\n");
        p = p->prox;
    }printArray(p->values,BSize);
}

Answer 1

您没有将 NULL 分配给 int *。您将其分配给 int。

remover 的类型为 int *，而 *remover 取消引用该指针，并且类型为 int。

将该行更改为以下内容:

remover = NULL;

实际上，您可以完全删除该行，因为在该点之后不再引用 remover。