c - 合并内存并处理 C 中的指针运算

Question

在下面的代码中，我不知道为什么我从不输入if。对我来说，它进入 if 是有道理的：

void Mem_Coalesce(){


    list_t* temp;
    temp = freep;
        if(free_node_count == 2){
        //will finish
             printf("Addr of temp is  %llx\n\n", (long long unsigned) temp);
                 printf("Size of Temp is  %d\n\n", temp->size);
             printf("Addr of end of temp free node space is  %llx\n\n", (long long unsigned) ((char*)temp + temp->size));
             printf("Addr of start temp->next  is  %llx\n\n", (long long unsigned) temp->next);
        if( ((char*)temp + (temp->size)) == (char*)(temp->next)){
                printf("Entered the if statement\n");
                        temp->size += (temp->next)->size;
                temp->next = NULL;
        }


    }else {

        while(temp->next != NULL  ){

            if( ((char*)temp + (temp->size)) == (char*)(temp->next)){

                temp->size += (temp->next)->size;
                                printf("coalesced size is %d temp->size \n", temp->size);
                temp->next = (temp->next)->next;
                ((temp->next)->next)->prev = temp;
            }
            temp=temp->next;

        }

    }



}

结果是

Addr of temp is  7f9c1e89b070

Size of Temp is  200

Addr of end of temp free node space is  7f9c1e89b138

Addr of start temp->next  is  7f9c1e89b278

如您所见，它永远不会进入if statement。也让我知道是否有任何其他可能更有效的内存合并算法。

Answer 1

您temp->size在这里以十进制打印：

printf("Size of Temp is  %d\n\n", temp->size);
                         ^^

当您以十六进制打印指针值时：

printf("Addr of temp is  %llx\n\n", (long long unsigned) temp);
                         ^^^^ 

200十进制是C8十六进制和0xC8+ 0x70= 0x138。因此，当您将结果添加0xC8到不等于时，因此您不输入if语句。0x7f9c1e89b0700x7f9c1e89b1380x7f9c1e89b278