Realloc导致程序崩溃
目前正在尝试编写基于菜单的程序，要求用户输入学生记录，在输入初始记录后，我希望用户可以选择添加更多记录槽但是当我尝试重新分配我的2d指针数组时，我的程序崩溃，特别是在第二个function之后调用。
#include #include #include #define LENGTH 21 void printRecords(int* size, char **fistName, char **lastName, float *grade); void addRecord(int* size, char** firstName, char** lastName, float *grade); int main(void) { /* Minimum measure check */ int size = 0, *check = (int*)malloc(sizeof(int)); *check = 1; while (check) { printf("Please indicate number of records you want to enter (min 5): "); scanf("%d", &size); if (size < 5) printf("Size entered was below the minimum.\n"); else check = 0; } free(check); /* Dynamic Memory Allocation */ char **firstName = (char**)malloc(size * sizeof(char*)), **lastName = (char**)malloc(size * sizeof(char*)); float *grade = (float*)malloc(size * sizeof(float)); int i; for (i = 0; i < size; i++) { firstName[i] = (char*)malloc(LENGTH * sizeof(char)); lastName[i] = (char*)malloc(LENGTH * sizeof(char)); } printf("Please input records of students (enter a new line after each record),\nwith following format first name last name score:\n"); for (i = 0; i < size; (i)++) scanf("%s %s %f", &firstName[i][0], &lastName[i][0], &grade[i]); int option = 1; while (option != 0) { /* Option Menu */ printf("Print records (press 1)\nAdd new record(press 2)\nDelete record(s)(press 3)\nSeach by last name(press 4)\nSort by score(press 5)\nSort by last name(press 6)\nFind the median score(press 7)\nExit the program(press 0)\n"); scanf("%d", &option); switch (option) { case 1: printRecords(&size, firstName, lastName, grade); break; case 2: addRecord(&size, firstName, lastName, grade); break; case 3: break; case 4: break; case 5: break; case 6: break; case 7: break; } } return 0; } void printRecords(int* size, char **firstName, char **lastName, float grade[]) { /* Option 1 */ int i; for (i = 0; i < *size; i++) printf("First Name : %s, Last Name : %s, Score : %.2f\n", firstName[i], lastName[i], grade[i]); } void addRecord(int* size, char** firstName, char** lastName, float* grade) { /* Option 2 */ char **a; float *c; (*size) += 1; a = (char **)realloc(firstName, *size * sizeof(char*)); /* Error */ if (a != NULL) //realloc was successful firstName = a; else //there was an error a = (char **)realloc(lastName, *size * sizeof(char*)); if (a != NULL) //realloc was successful lastName = a; else; //there was an error c = (float *)realloc(grade, *size * sizeof(float*)); grade = c; firstName[*size - 1] = (char*)malloc(LENGTH * sizeof(char)); lastName[*size - 1] = (char*)malloc(LENGTH * sizeof(char)); scanf("%s %s %f", &firstName[*size][0], &lastName[*size][0], &grade[*size]); } 编辑错过了一个错误; 导致lastName未被重新分配
if (a != NULL) //realloc was successful firstName = a; else //there was an error <<-- missing ; a = (char **)realloc(lastName, *size * sizeof(char*)); // <<-- executed under "else"
实际上， lastName被赋予与firstName相同的值，具有以下内容
if (a != NULL) //realloc was successful lastName = a;
另外，关于您使用check的评论。 输入循环有些问题。 为简单的int分配内存是非常必要的。 您甚至不使用check作为指针（ check = 0;将导致free()失败，并导致内存泄漏）。
int size = 0, *check = (int*)malloc(sizeof(int)); *check = 1; while (check) { // <==== error should be *check printf("Please indicate number of records you want to enter (min 5): "); scanf("%d", &size); if (size < 5) printf("Size entered was below the minimum.\n"); else check = 0; // <==== error should be *check } free(check);
这会更容易，你甚至不需要check 。
int size; do { printf("Please indicate number of records you want to enter (min 5): "); scanf("%d", &size); if (size < 5) printf("Size entered was below the minimum.\n"); } while (size < 5);
C是按值传递的。
返回函数后，应用于addREcord()中firstName和lastName的更改将丢失，因为这两个vairbales将作为参数传递的变量的copeis带入addRecord()调用。
从中更改addRecord()的定义
void addRecord(int* size, char** firstName, char** lastName, float* grade);
成为
void addRecord(int* size, char*** pfirstName, char*** plastName, float* grade);
在addRecord()里面用(*pfirstName) addRecord()替换所有firstName用(*pfirstName) addRecord()替换所有lastName
（足够有针对性地做了正确的size 。）
像这样调用addRecord() ：
addRecord(&size, &firstName, &lastName, grade);