[英]I'm receiving Invalid read of size 8 when running Valgrind in C
[英]Trying to use a double pointer struct to read a csv file and print off the entries but I'm getting "Invalid read of size 8" in C
創建 C 程序以將 csv 文件讀入雙指針結構,但出現分段錯誤。
這是結構:
typedef struct vehicle{
char *make;
char *model;
char *color;
char *license_plate;
int year;
}vehicle_t;
我在這個程序中使用了單指針和雙指針來更好地理解使用指針:
vehicle_t *v = NULL;
vehicle_t **car;
car = calloc(1, sizeof(vehicle_t *));
int num_cars = 0;
while(!fgets(buffer, BUF_SIZE, fp)){
//car = calloc(1, sizeof(vehicle_t *));
*(car+num_cars) = calloc(1, sizeof(vehicle_t));
*((car)+num_cars) = read_csv(fp, v);
num_cars++;
//free(v->year);
free(v->make);
free(v->model);
free(v->color);
free(v->license_plate);
free(v);
}
這是我創建的 function 以讀取 csv 文件並將其返回到汽車中:
vehicle_t *read_csv(FILE *fp, vehicle_t *v){
char buffer[BUF_SIZE] = {0};
v = calloc(1, sizeof(vehicle_t));
fgets(buffer, BUF_SIZE, fp);
char *tok = strtok(buffer, ",");
(v)->year = atoi(tok);
tok = strtok(NULL, ",");
(v)->make = calloc(strlen(tok)+1, sizeof(char));
tok = strtok(NULL, ",");
strcpy((v)->make, tok);
(v)->model = calloc(strlen(tok)+1, sizeof(char));
strcpy((v)->model, tok);
tok = strtok(NULL, ",");
(v)->color = calloc(strlen(tok)+1, sizeof(char));
strcpy((v)->color, tok);
tok = strtok(NULL, ",");
(v)->license_plate = calloc(strlen(tok)+1, sizeof(char));
strcpy((v)->license_plate, tok);
return v;
}
Valgrind 告訴我,當我嘗試從雙指針汽車打印車輛時,我遇到了一個問題:
for(int i= 0; i<=num_cars; i++){
printf("%d %s %s (%s) LIC:%s\n", ((*car)->year), ((*car)->make), ((*car)- >model), ((*car)->color), ((*car)->license_plate));
}
Valgrind 錯誤信息:
我通過釋放汽車雙指針來完成代碼:
for(int i= 0; i<=num_cars; i++){
//free((*car)->year);
free((*car)->make);
free((*car)->model);
free((*car)->color);
free((*car)->license_plate);
free(*car);
free(car);
}
不知道為什么我會遇到分段錯誤。 以為我對指針使用有一個不錯的處理,並且看起來像正確分配和釋放 memory。
至少有這些問題:
錯誤的指針
(v)->make = calloc(strlen(tok)+1, sizeof(char));
tok = strtok(NULL, ","); // ????
strcpy((v)->make, tok);
代碼很奇怪。 為什么要分配一個字符串長度,然后在復制之前更改tok
?
我期待更多類似的東西
(v)->make = calloc(strlen(tok)+1, sizeof(char));
strcpy((v)->make, tok);
tok = strtok(NULL, ",");
研究strdup()
以獲取替代代碼。
只有 1 輛車,錯誤的fgets()
用法
代碼僅分配給 1 輛車
//vehicle_t **car;
//car = calloc(1, sizeof(vehicle_t *));
//int num_cars = 0;
//while(!fgets(buffer, BUF_SIZE, fp)){
// *(car+num_cars) = calloc(1, sizeof(vehicle_t));
// *((car)+num_cars) = read_csv(fp, v);
int car_n = 1000;
// n cars
vehicle_t **car = calloc(car_n, sizeof *car);
int num_cars = 0;
// v --- no !
while(num_cars < car_n && fgets(buffer, BUF_SIZE, fp)){
car[num_cars] = calloc(1, sizeof car[num_cars][0]);
car[num_cars] = read_csv(fp, v);
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