制作链表时出现Segmentation fault (core dumped)错误
Segmentation fault (core dumped) error when making a linked list
我正在为学校学习 C,其中一项作业是创建数据库。现在我试图将我给它的一些输入添加到列表中,但我不断收到分段错误。我做错了什么?
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
struct carinfo_t {
char* carbrand;
char* carmodel;
int caryear;
float carvalue;
struct carinfo_t * next;
};
struct carinfo_t * carbase;
struct carinfo_t * tempcar;
struct carinfo_t * tempcar2;
struct carinfo_t * tempprint;
void freeCarinfo(struct carinfo_t * carinfo){
free(carinfo->carbrand);
free(carinfo->carmodel);
free(carinfo);
}
struct carinfo_t * createCarinfo(char *carbrand, char *carmodel, int caryear, float carvalue){
struct carinfo_t * newcar;
newcar = (struct carinfo_t *)malloc(sizeof (struct carinfo_t));
newcar->carbrand=(char *)malloc(sizeof(char)*(strlen(carbrand) + 1));
strcpy(newcar->carbrand, carbrand);
newcar->carmodel=(char *)malloc(sizeof(char)*(strlen(carmodel) + 1));
strcpy(newcar->carmodel, carmodel);
newcar->caryear=caryear;
newcar->carvalue=carvalue;
newcar->next= NULL;
return newcar;
}
struct carinfo_t * addCarinfo(struct carinfo_t *carbase, struct carinfo_t *newcar){
if(carbase=NULL){
carbase = newcar;
return carbase;
}
else{
tempcar2->next=carbase;
carbase=tempcar2;
return carbase;
}
}
void printCarbase(struct carinfo_t *carbase){
struct carinfo_t *tempprint = carbase;
if (carbase == NULL){
printf("The database contains no cars\n");
}
else{
while (tempprint != NULL){
printf("Car:\n");
printf("- brand: %s\n", carbase->carbrand);
printf("- model: %s\n", carbase->carmodel);
printf("- year: %d\n", carbase->caryear);
printf("- value: %7.2f\n", carbase->carvalue);
tempprint = tempprint->next;
}
}
}
void main(void){
struct carinfo_t * carbase;
carbase = NULL;
struct carinfo_t * tempcar;
tempcar = createCarinfo("Opel", "Manta", 1965, 20000);
struct carinfo_t * tempcar2 = createCarinfo("Ford", "Focus", 1999, 350.25);
addCarinfo(carbase, tempcar);
}
此外,如果您发现任何改进我的代码的方法,请告诉我,我是编程的新手,我希望能够正确地做到这一点。
编辑:感谢所有回复的人,我想出了如何使用 GDB。现在原来的问题已经解决了,我得到了同样的错误,但这次似乎是 "tempcar2" 的问题:
Program received signal SIGSEGV, Segmentation fault.
0x000000000040072a in addCarinfo (carbase=0x602010, newcar=0x602080)
at database.c:56
56 tempcar2 = tempcar2->next;
(gdb) bt
#0 0x000000000040072a in addCarinfo (carbase=0x602010, newcar=0x602080)
at database.c:56
#1 0x0000000000400869 in main () at database.c:98
我运行你在gdb中的程序它指向第52行
Program received signal SIGSEGV, Segmentation fault.
0x00000000004007b6 in addCarinfo (carbase=0x0, newcar=0x602010) at so.c:52
(gdb) bt
#0 0x00000000004007b6 in addCarinfo (carbase=0x0, newcar=0x602010) at so.c:52
#1 0x00000000004008e7 in main () at so.c:89
这是错误的,而不是==你使用=。
// Your assigning carbase struct pointer to NULL instead of validating pointer is null.
if(carbase=NULL){ //change to carbase == NULL
carbase = newcar;
return carbase;
}
如何使用GDB调试:
- 如果您使用 gcc,请使用 -g 标志编译您的 C 代码。
示例:
gcc -g file.c
- gdb ./a.out
- bt(回溯如果将指出调用堆栈)
您的代码中存在一些问题:
- 一些变量没有初始化(
tempcar2
例如,它是全局的)
- 一些局部变量和全局变量同名
- 一些比较是使用
=
而不是 ==
运算符
- 在你的打印函数中,你总是打印
carbase
而不是 tempprint
malloc
return投,it should not
编译器可能已经检测到一些问题:打开编译器警告(-Wall
对于大多数编译器)
当您的代码编译时带有警告,您的问题就会暴露出来:
.code.tio.c: In function ‘addCarinfo’:
.code.tio.c:46:8: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
if(carbase=NULL){
^~~~~~~
.code.tio.c: At top level:
.code.tio.c:81:6: warning: return type of ‘main’ is not ‘int’ [-Wmain]
void main(void){
^~~~
.code.tio.c: In function ‘main’:
.code.tio.c:88:24: warning: unused variable ‘tempcar2’ [-Wunused-variable]
struct carinfo_t * tempcar2 = createCarinfo("Ford", "Focus", 1999, 350.25);
^~~~~~~~
更正后的版本可能是:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
struct carinfo_t
{
char* carbrand;
char* carmodel;
int caryear;
float carvalue;
struct carinfo_t * next;
};
void freeCarinfo(struct carinfo_t * carinfo)
{
free(carinfo->carbrand);
free(carinfo->carmodel);
free(carinfo);
}
struct carinfo_t * createCarinfo(char *carbrand, char *carmodel, int caryear, float carvalue)
{
struct carinfo_t * newcar;
/* malloc cast is not recommender */
newcar = malloc(sizeof (struct carinfo_t));
/* strdup can be used here */
newcar->carbrand = strdup(carbrand);
newcar->carmodel = strdup(carmodel);
newcar->caryear=caryear;
newcar->carvalue=carvalue;
newcar->next= NULL;
return newcar;
}
struct carinfo_t * addCarinfo(struct carinfo_t *carbase, struct carinfo_t *newcar)
{
if(carbase==NULL)
{
carbase = newcar;
return carbase;
}
else
{
/* find for the last element */
struct carinfo_t * tempcar2 = carbase;
while(tempcar2->next)
{
tempcar2 = tempcar2->next;
}
/* add the new car to the list */
tempcar2->next=newcar;
return carbase;
}
}
void printCarbase(struct carinfo_t *carbase)
{
struct carinfo_t *tempprint = carbase;
if (carbase == NULL)
{
printf("The database contains no cars\n");
}
else
{
while (tempprint != NULL)
{
printf("Car:\n");
printf("- brand: %s\n", tempprint->carbrand);
printf("- model: %s\n", tempprint->carmodel);
printf("- year: %d\n", tempprint->caryear);
printf("- value: %7.2f\n", tempprint->carvalue);
tempprint = tempprint->next;
}
}
}
int main(void)
{
struct carinfo_t * carbase;
carbase = NULL;
struct carinfo_t * tempcar;
tempcar = createCarinfo("Opel", "Manta", 1965, 20000);
struct carinfo_t * tempcar2 = createCarinfo("Ford", "Focus", 1999, 350.25);
carbase = addCarinfo(carbase, tempcar);
carbase = addCarinfo(carbase, tempcar2);
printCarbase(carbase);
return 0;
}
此代码的结果是:
Car:
- brand: Opel
- model: Manta
- year: 1965
- value: 20000.00
Car:
- brand: Ford
- model: Focus
- year: 1999
- value: 350.25
我正在为学校学习 C,其中一项作业是创建数据库。现在我试图将我给它的一些输入添加到列表中,但我不断收到分段错误。我做错了什么?
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
struct carinfo_t {
char* carbrand;
char* carmodel;
int caryear;
float carvalue;
struct carinfo_t * next;
};
struct carinfo_t * carbase;
struct carinfo_t * tempcar;
struct carinfo_t * tempcar2;
struct carinfo_t * tempprint;
void freeCarinfo(struct carinfo_t * carinfo){
free(carinfo->carbrand);
free(carinfo->carmodel);
free(carinfo);
}
struct carinfo_t * createCarinfo(char *carbrand, char *carmodel, int caryear, float carvalue){
struct carinfo_t * newcar;
newcar = (struct carinfo_t *)malloc(sizeof (struct carinfo_t));
newcar->carbrand=(char *)malloc(sizeof(char)*(strlen(carbrand) + 1));
strcpy(newcar->carbrand, carbrand);
newcar->carmodel=(char *)malloc(sizeof(char)*(strlen(carmodel) + 1));
strcpy(newcar->carmodel, carmodel);
newcar->caryear=caryear;
newcar->carvalue=carvalue;
newcar->next= NULL;
return newcar;
}
struct carinfo_t * addCarinfo(struct carinfo_t *carbase, struct carinfo_t *newcar){
if(carbase=NULL){
carbase = newcar;
return carbase;
}
else{
tempcar2->next=carbase;
carbase=tempcar2;
return carbase;
}
}
void printCarbase(struct carinfo_t *carbase){
struct carinfo_t *tempprint = carbase;
if (carbase == NULL){
printf("The database contains no cars\n");
}
else{
while (tempprint != NULL){
printf("Car:\n");
printf("- brand: %s\n", carbase->carbrand);
printf("- model: %s\n", carbase->carmodel);
printf("- year: %d\n", carbase->caryear);
printf("- value: %7.2f\n", carbase->carvalue);
tempprint = tempprint->next;
}
}
}
void main(void){
struct carinfo_t * carbase;
carbase = NULL;
struct carinfo_t * tempcar;
tempcar = createCarinfo("Opel", "Manta", 1965, 20000);
struct carinfo_t * tempcar2 = createCarinfo("Ford", "Focus", 1999, 350.25);
addCarinfo(carbase, tempcar);
}
此外,如果您发现任何改进我的代码的方法,请告诉我,我是编程的新手,我希望能够正确地做到这一点。
编辑:感谢所有回复的人,我想出了如何使用 GDB。现在原来的问题已经解决了,我得到了同样的错误,但这次似乎是 "tempcar2" 的问题:
Program received signal SIGSEGV, Segmentation fault.
0x000000000040072a in addCarinfo (carbase=0x602010, newcar=0x602080)
at database.c:56
56 tempcar2 = tempcar2->next;
(gdb) bt
#0 0x000000000040072a in addCarinfo (carbase=0x602010, newcar=0x602080)
at database.c:56
#1 0x0000000000400869 in main () at database.c:98
我运行你在gdb中的程序它指向第52行
Program received signal SIGSEGV, Segmentation fault.
0x00000000004007b6 in addCarinfo (carbase=0x0, newcar=0x602010) at so.c:52
(gdb) bt
#0 0x00000000004007b6 in addCarinfo (carbase=0x0, newcar=0x602010) at so.c:52
#1 0x00000000004008e7 in main () at so.c:89
这是错误的,而不是==你使用=。
// Your assigning carbase struct pointer to NULL instead of validating pointer is null.
if(carbase=NULL){ //change to carbase == NULL
carbase = newcar;
return carbase;
}
如何使用GDB调试:
- 如果您使用 gcc,请使用 -g 标志编译您的 C 代码。
示例:
gcc -g file.c
- gdb ./a.out
- bt(回溯如果将指出调用堆栈)
您的代码中存在一些问题:
- 一些变量没有初始化(
tempcar2
例如,它是全局的) - 一些局部变量和全局变量同名
- 一些比较是使用
=
而不是==
运算符 - 在你的打印函数中,你总是打印
carbase
而不是tempprint
malloc
return投,it should not
编译器可能已经检测到一些问题:打开编译器警告(-Wall
对于大多数编译器)
当您的代码编译时带有警告,您的问题就会暴露出来:
.code.tio.c: In function ‘addCarinfo’:
.code.tio.c:46:8: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
if(carbase=NULL){
^~~~~~~
.code.tio.c: At top level:
.code.tio.c:81:6: warning: return type of ‘main’ is not ‘int’ [-Wmain]
void main(void){
^~~~
.code.tio.c: In function ‘main’:
.code.tio.c:88:24: warning: unused variable ‘tempcar2’ [-Wunused-variable]
struct carinfo_t * tempcar2 = createCarinfo("Ford", "Focus", 1999, 350.25);
^~~~~~~~
更正后的版本可能是:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
struct carinfo_t
{
char* carbrand;
char* carmodel;
int caryear;
float carvalue;
struct carinfo_t * next;
};
void freeCarinfo(struct carinfo_t * carinfo)
{
free(carinfo->carbrand);
free(carinfo->carmodel);
free(carinfo);
}
struct carinfo_t * createCarinfo(char *carbrand, char *carmodel, int caryear, float carvalue)
{
struct carinfo_t * newcar;
/* malloc cast is not recommender */
newcar = malloc(sizeof (struct carinfo_t));
/* strdup can be used here */
newcar->carbrand = strdup(carbrand);
newcar->carmodel = strdup(carmodel);
newcar->caryear=caryear;
newcar->carvalue=carvalue;
newcar->next= NULL;
return newcar;
}
struct carinfo_t * addCarinfo(struct carinfo_t *carbase, struct carinfo_t *newcar)
{
if(carbase==NULL)
{
carbase = newcar;
return carbase;
}
else
{
/* find for the last element */
struct carinfo_t * tempcar2 = carbase;
while(tempcar2->next)
{
tempcar2 = tempcar2->next;
}
/* add the new car to the list */
tempcar2->next=newcar;
return carbase;
}
}
void printCarbase(struct carinfo_t *carbase)
{
struct carinfo_t *tempprint = carbase;
if (carbase == NULL)
{
printf("The database contains no cars\n");
}
else
{
while (tempprint != NULL)
{
printf("Car:\n");
printf("- brand: %s\n", tempprint->carbrand);
printf("- model: %s\n", tempprint->carmodel);
printf("- year: %d\n", tempprint->caryear);
printf("- value: %7.2f\n", tempprint->carvalue);
tempprint = tempprint->next;
}
}
}
int main(void)
{
struct carinfo_t * carbase;
carbase = NULL;
struct carinfo_t * tempcar;
tempcar = createCarinfo("Opel", "Manta", 1965, 20000);
struct carinfo_t * tempcar2 = createCarinfo("Ford", "Focus", 1999, 350.25);
carbase = addCarinfo(carbase, tempcar);
carbase = addCarinfo(carbase, tempcar2);
printCarbase(carbase);
return 0;
}
此代码的结果是:
Car:
- brand: Opel
- model: Manta
- year: 1965
- value: 20000.00
Car:
- brand: Ford
- model: Focus
- year: 1999
- value: 350.25