C: valgrind 显示结构中双指针枚举的无效写入

Question

在我的 test.c 中，我有：

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

enum MyEnum{
    H1 = '#',
    H2 = '$'
};

typedef struct {
    enum MyEnum** myenum;
    int myint;
    char *s;
} MyStruct;

MyStruct* somefunction(const char* fp){
    FILE* file = fopen(fp, "r");
        if(!file){
        fprintf(stderr, "Error %s not found", fp);
        exit(-1);
    }
    char line[100] = {0};
    int i = 0;
    fgets(line, 100, file);
    sscanf(line, "%i", &i);
    MyStruct* strct = (MyStruct *) malloc(sizeof(strct));
    strct->myint = i;
    printf("%i\n", strct->myint);

    fclose(file);
    free(strct);
    return strct;
}


int main(int argc, char** argv){
  char* fp = argv[1];
  somefunction(fp);
  bool run = true;
  while(run){
    char entry = fgetc(stdin);
    
    switch(entry){ 
      case 'q' :{
        run = false;
        break;                      
      }
    }
  }
}

我的 test.txt 包含：

1234
5678

运行 Valgrind 给予：

1234
q
==2030==
==2030== HEAP SUMMARY:
==2030== HEAP SUMMARY:
==2030==     in use at exit: 0 bytes in 0 blocks
==2030==   total heap usage: 5 allocs, 5 frees, 6,704 bytes allocated
==2030==
==2030== All heap blocks were freed -- no leaks are possible
==2030==
==2030== ERROR SUMMARY: 2 errors from 2 contexts (suppressed: 0 from 0)
==2030==
==2030== 1 errors in context 1 of 2:
==2030== Invalid read of size 4
==2030==    at 0x108AA9: somefunction (in /root/SokobanTechDev/test)
==2030==    by 0x108B03: main (in /root/SokobanTechDev/test)
==2030==  Address 0x51de2f8 is 0 bytes after a block of size 8 alloc'd
==2030==    at 0x4C2D0AF: malloc (vg_replace_malloc.c:381)
==2030==    by 0x108A93: somefunction (in /root/SokobanTechDev/test)
==2030==    by 0x108B03: main (in /root/SokobanTechDev/test)
==2030==
==2030==
==2030== 1 errors in context 2 of 2:
==2030== Invalid write of size 4
==2030==    at 0x108AA2: somefunction (in /root/SokobanTechDev/test)
==2030==    by 0x108B03: main (in /root/SokobanTechDev/test)
==2030==  Address 0x51de2f8 is 0 bytes after a block of size 8 alloc'd
==2030==    at 0x4C2D0AF: malloc (vg_replace_malloc.c:381)
==2030==    by 0x108A93: somefunction (in /root/SokobanTechDev/test)
==2030==    by 0x108B03: main (in /root/SokobanTechDev/test)

为什么 valgrind 在定义枚举 MyEnum 后给我一个 invalid write？在我的结构中，如果我评论 enum MyEnum** myenum;，那些上下文就会消失。我推测他正在为 H1 和 H2 分配 2 个指针（每个指针 8 个字节），但是 malloc 不应该处理这个问题吗？

我试图寻找类似 here and 的答案，但我似乎找不到任何与双指针相关的东西。

提前致谢

Answer 1

函数中至少有两个错误。

第一个是内存分配不正确

MyStruct* strct = (MyStruct *) malloc(sizeof(strct));

你需要写任何一个

MyStruct* strct = (MyStruct *) malloc(sizeof(*strct));

或

MyStruct* strct = (MyStruct *) malloc(sizeof(MyStruct));

并在调用 free 后返回具有无效值的指针

    //...
    free(strct);
    return strct;
}

没有意义。

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