Question

我一直遇到分段错误，我从char指针知道它。但我无法弄清楚为什么？

Whiskey* createWhiskey(int a, double p, char* n){

    Whiskey* whiskey = malloc(sizeof(Whiskey));
    whiskey->age = a;
    whiskey->proof = p;
    whiskey->name = malloc((strlen(n)+1) * sizeof(char));
    strcpy(whiskey->name, n);
    return whiskey;
}
int main(){

    Whiskey* burbon;
    burbon = createWhiskey(12, 90.0, "MakersMark");

    free(burbon);

    return 0;
}

在Alex的评论中（见下文），添加了以下信息：

typedef struct{ int age; double proof; char* name; }Whiskey;

Answer 1

正如评论中所讨论的，所显示的程序很好。

但是，您应该添加一些检查以避免出现问题。类似的东西：

typedef struct{ int age; double proof; char* name; } Whiskey;

Whiskey* createWhiskey(int a, double p, char* n){
    Whiskey* whiskey = malloc(sizeof(Whiskey));
    if (whiskey) 
    {
        whiskey->age = a;
        whiskey->proof = p;
        if (strlen(n) > SOME_MAXIMUM)
        {
            free(whiskey);
            printf("Some error... maybe\n");
            return NULL;
        }
        whiskey->name = malloc((strlen(n)+1) * sizeof(char));
        if (whiskey->name)
        {
            strcpy(whiskey->name, n);
        }
        else
        {
            free(whiskey);
            printf("Some error... \n");
            return NULL;
        }
    }
    return whiskey;
}

int main(){

    Whiskey* burbon;
    burbon = createWhiskey(12, 90.0, "MakersMark");
    if (!burbon)
    {
        printf("Some error... \n");
    }    

    // code....

    if (burbon)
    {
        free( burbon->name);
        free(burbon);
    }
    return 0;
}

Answer 2

我希望你的威士忌结构的定义很好。以下代码对我来说很好：

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
typedef struct Whisk {
        int age;
        double proof;
        char *name;
} Whiskey;
Whiskey* createWhiskey(int a, double p, char* n){

    Whiskey* whiskey = malloc(sizeof(Whiskey));
    whiskey->age = a;
    whiskey->proof = p;
    whiskey->name = malloc((strlen(n)+1) * sizeof(char));
    strcpy(whiskey->name, n);
    return whiskey;
}

int main(){

    Whiskey* burbon;
    burbon = createWhiskey(12, 90.0, "MakersMark");
    if (!burbon)
    {
        printf("Some error... \n");
    }

    // code....

    if (burbon)
    {
        free( burbon->name);
        free(burbon);
    }
    return 0;
}

Answer 3

以下代码

干净地编译
执行适当的错误检查
在运行时不会出错;
执行所需的功能
通过将分配的内存指针传递给free()
为传递的参数使用有意义的名称

代码：

#include <string.h>  // malloc()
#include <stdlib.h>  // exit(), EXIT_FAILURE
#include <stdio.h>   // perror()

typedef struct
{
    int age;
    double proof;
    char* name;
} Whiskey;

Whiskey* createWhiskey(int age, double proof, char* name)
{

    Whiskey* whiskey = NULL;
    if( NULL == (whiskey = malloc(sizeof(Whiskey)) ) )
    { // then, malloc failed
        perror( "malloc for Whiskey failed" );
        exit( EXIT_FAILURE );
    }

    // implied else, malloc successful

    whiskey->age = age;
    whiskey->proof = proof;
    whiskey->name = NULL;

    if( NULL == (whiskey->name = malloc( strlen(name)+1) ) )
    { // then malloc failed
        perror( "malloc for name field failed" );
        free( whiskey );
        exit( EXIT_FAILURE );
    }

    // implied else, malloc successful

    strcpy(whiskey->name, name);
    return whiskey;
} // end function: createWhiskey


int main( void )
{

    Whiskey* burbon;
    burbon = createWhiskey(12, 90.0, "MakersMark");

    free( burbon->name );
    free( burbon );

    return 0;
} // end function: main

Seg Fault，malloc char指针

3 个答案: