線程1：C中的EXC_BAD_ACCESS（代碼= 1，地址= 0x0）

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線程1：EXC_BAD_ACCESS（代碼= 1，地址= 0x0）

每當我嘗試掃描從輸入到char *變量的字符串時。 我不知道為什么會發生，因為一切似乎都正確。

#include <stdio.h>
#include <string.h>
#include <time.h>
#include <stdlib.h>

頭

struct date {
    int year;
    int month;
    int day;
};

日期結構

struct patientData {
    unsigned int code;
    char name[11];
    char family[21];
    unsigned int age;
    char MF;
    char disease[11];
    unsigned int numOfVisits;
    struct date *date1;
    struct date *date2;
    struct date *date3;
    struct patientData *nextPtr;

};

患者數據結構

int isEmpty (struct patientData *sPtr);
void visit ( struct patientData **returned , unsigned int code);
void Insert (struct patientData **sPtr, unsigned int code , char *name , char *family , unsigned int age ,char gender, int tmgh);
void insertDisease (struct patientData **sPtr   , char *name , char *family , char *disease );
struct patientData *searchCode (struct patientData **sPtr  , unsigned int code, int *returnval);
struct patientData *searchName (struct patientData **sPtr , char *name  , char *family);
void searchDate (struct patientData **sPtr , int year , int month , int day );
void delete (struct patientData **sPtr  );
void report (struct patientData **sPtr  );

職能; 這里（主要）是發生問題的地方。

int main() {

    char *choice;

    unsigned int code;
    char name[11];
    char family[21];;
    char disease[11];
    int searchCodeReturnValue;
    unsigned int age;
    char gender;
    int tmgh;
    int year , month , day;

    struct patientData *startPtr = NULL;


    puts("Enter one of the following options:");
    puts("Visit");
    puts("InsertDisease");
    puts("search");
    puts("Delete");
    puts("END");

    scanf("%s",choice);
    while (strcmp(choice, "END") != 0) {
        if (strcmp(choice, "Visit") == 0) {
            printf("Enter the code:\n");
            scanf("%5ui",&code);
            struct patientData *a = searchCode(&startPtr,code,&searchCodeReturnValue);
            if (searchCodeReturnValue == 1){
                visit(&a , code);
            }
            else if (searchCodeReturnValue == 0){
                printf("Enter name:\n");
                scanf("%10s",name);
                printf("Enter family:\n");
                scanf("%20s",family);
                printf("Enter age:\n");
                scanf("%ui",&age);
                printf("Enter gender:\n");
                scanf("%c",&gender);
                printf("Enter num of last visits:\n");
                scanf("%i",&tmgh);
                Insert(&startPtr , code , name , family , age , gender , tmgh);

            }
        }
        else if ( strcmp(choice, "InsertDisease")== 0) {
            printf("Enter name:\n");
            scanf("%10s",name);
            printf("Enter family:\n");
            scanf("%20s",family);
            printf("Enter disease:\n");
            scanf("%10s",disease);
            struct patientData *namesearch = searchName(&startPtr, name, family);
            insertDisease ( &namesearch , name , family , disease );
        }
        else if (strcmp(choice, "Search")== 0) {
            puts("Choose the way you wanna search: \n 1- by code \n 2- by first and last name \n 3- by Date");
            int choiceNum;
            scanf("%i",&choiceNum);
            if (choiceNum == 1) {
                printf("Enter the code:\n");
                scanf("%5ui",&code);
                searchCode(&startPtr, code , &searchCodeReturnValue);
            }
            else if ( choiceNum == 2){
                printf("Enter name:\n");
                scanf("%10s",name);
                printf("Enter family:\n");
                scanf("%20s",family);
                searchName(&startPtr ,name , family );
            }
            else if ( choiceNum == 3){
                printf("Enter year:\n");
                scanf("%i",&year);
                printf("Enter month:\n");
                scanf("%i",&month);
                printf("Enter day:\n");
                scanf("%i",&day);
                searchDate(&startPtr , year , month , day);
            }
            else
                puts("Wrong entry");
        }
        else if (strcmp(choice, "delete")== 0) {
            delete(&startPtr);
        }
        else if (strcmp(choice, "Report") == 0) {
            report(&startPtr);
        }
        else if (strcmp(choice, "END") == 0)
            return 0;

        else{
            puts("wrong!");
            return 0;
        }
    }
    return 0;
}

Answer 1

char *choice;

內存未分配給指針，您正在執行

scanf("%s",choice);

將內存分配給指針，然后嘗試掃描其值。

choice = malloc(30); /* Size can be anything of your wish */

因此，您正在訪問未初始化的指針，這將導致未定義的行為。

使用完此存儲器后，您需要釋放它

free(choice);

Answer 2

您正在取消引用無效的指針， choice被聲明為char指針並且從未初始化，您不需要將其作為char指針，也可以將choice聲明為char數組，因此它所包含的最長字符串似乎是"InsertDisease" ，因為它有13個字符，所以以這種方式聲明choice

char choice[14];

並將scanf更改為

scanf("%13s", choice);

這樣，您可以防止緩沖區溢出和內存泄漏（ 如果以后沒有正確free choice ，則可能是由於使用malloc造成的 ）。

我看到您也沒有重新掃描choice值，這將使循環無限，您應該將其添加到循環的頂部，並在循環外將其刪除，然后將循環寫為

while (1) {
    scanf("%13s", choice);
    .
    .
   /* check the content of choice with strcmp and process the requested command */
    .
    .
}

在循環中，您有一個if (strcmp(choice, "END") == 0) return 0; 因此應該注意結束循環。