c - malloced 指针中的内存泄漏？

Question

我遇到了两个似乎无法解决的内存泄漏实例。第一个实例发生在 char *temp = (char*)malloc(sizeof(char*)); ，我在 if 语句的开头使用了这个变量，并确保在最后释放它，但我仍然遇到泄漏。第二个发生在 s = create();和 s = (Stack*)malloc(sizeof(Stack)); .

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

typedef struct{
    char **data;
    int top;
    int size;
}Stack;
typedef enum { FALSE, TRUE } bool;
Stack* create(){
    Stack *s;
    s = (Stack*)malloc(sizeof(Stack));
    s->top = -1;
    s->size = 10;
    s->data = (char**)malloc(s->size*sizeof(char*));
    return s;
}
void deleteStack(Stack* ps){
    if(ps == NULL){
        printf("No memory allocated in Stack.\n");
    }
    while(ps->top >= 0){
        free(ps->data[ps->top]);
        ps->top--;
    }
    free(ps->data);
}
bool full( Stack s){
    if(s.top == s.size-1)
        return TRUE;
    return FALSE;
}
void push( Stack* ps, char* str){
    if(full(*ps)){
        int tempsize = ps->size;
        ps->size += 10;
        ps->data = realloc(ps->data, ps->size * sizeof(char*));
    //  char **temp = realloc(ps->data, ps->size*sizeof(char*));
    //  if(temp == NULL){
    //      perror("realloc");
    //      printf("Error! memory not allocated.\n");
    //      exit(-1);
    //  }
    //  ps->data = temp;
        printf("Stack capacity has grown from %d elements to %d elements\n", tempsize, ps->size);   
    }
    ps->data[++ps->top] = strdup(str);
}
bool empty( Stack s){
    if(s.top == -1)
        return TRUE;
    return FALSE;
}
char* pop( Stack* ps){
    if(empty(*ps))
        return NULL;
    return ps->data[ps->top--];
}
int main(int argc, char *argv[]){
    printf("Assignment 2 Problem 1 by Jasmine Ramirez\n\n");
    FILE *input = fopen("data_a2.txt", "r");
    if(input == NULL){
        perror("fopen");
        printf("File %s not found.\n", "data_a2.txt");
        exit(EXIT_FAILURE);
    }
    Stack *s;
    s = create();                <---16 bytes in 1 block definitely lost
    char str[255];
    char *temp = (char*)malloc(sizeof(char));   <---1 bytes in 1 block definitely lost
    int i = 0;
    while(fscanf(input, "%s\n", str) == 1){
        if(strcmp(str, "pop") == 0){
            temp = pop(s);
            i--;
            printf("# of elements after popping: %d\tstring popped: %s\n", i, temp);
            free(temp);
        }
        else{
            push(s, str);
            i++;    
        }
    }
    deleteStack(s);
    fclose(input);
    return 0;
}

我想不通 temp 中丢失 1 个字节的原因和 s应该由 deleteStack() 处理.

Answer 1

在这个声明中

temp = pop(s);

指向早期 malloc 内存的指针丢失，因此泄漏。

在 deleteStack 中，您还没有释放 ps，所以这也是一个泄漏，因为在 中分配给 Stack *s; 的内存>创建永远不会被释放。