C语言程序运行与调试输出不一致问题求助

问题现象 #

• 程序功能：从input.txt读取学生信息存入链表，按出生年份排序后打印
• 运行时输出无意义数字，每次结果不同
• 调试时输出完全正确

运行时输出 #

Student names in ascending order by birthday:
-2013265920000
M-2013265920-2013265920-2013265920-2013265920
Ali Pehlivan;2005
-2013265920-2013265920-20132659200

调试时输出 #

Student names in ascending order by birthday:
Ali Pehlivan;2005
Selami Kilic;2002
Esma Sultan;2001
Mehmet Ali Sarsil;2000

input.txt内容 #

040160811;Ali Pehlivan;2005
040180224;Mehmet Ali Sarsil;2000
820190040;Esma Sultan;2001
150190207;Selami Kilic;2002

完整代码 #

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

struct n {
    char number[9];
    char name;
    int year;
    struct n* next;
};
typedef struct n node;

struct s_node {
    char* number;
    struct s_node *next;
}*stack = NULL;

int isLetter(char character);
int isNumber(char character);
int charToInt(char character);
node** sortAndPrintByBirth(node* *list);
node** sortAndPrintByFaculty(node* *list);
int length(node** list);
void push(char* value);
char* pop();
void display();

int main() {
    node* Student;
    Student = (node *) malloc(sizeof(node));
    node* head1;
    node* head;
    head = Student;
    head1 = head;
    node* Students[100];

    FILE* file;
    file = fopen("C:\\Users\\PC\\CLionProjects\\untitled1\\input.txt", "r");
    char fchar;
    fchar = fgetc(file);
    int switchNY = 0; // 0 for school number, 1 for birth year
    int studentCounter = 0;
    while(fchar != EOF){
        if(isLetter(fchar)){
            head1->name = fchar;
            head1->year = (int) NULL;
            head1->next = malloc(sizeof(node*));
            head1 = head1->next;
            fchar = fgetc(file);
        }else if(isNumber(fchar)){
            if(switchNY == 0){
                for(int i = 0; i < 9; i++){
                    head1->number[i] = fchar;
                    head1->year =(int) NULL;
                    head1->number[i+1] = (char) NULL;
                    fchar = fgetc(file);
                }
            }else {
                for (int i = 0; i < 4; i++) {
                    head1->year = charToInt(fchar);
                    head1->next = malloc(sizeof(node *));
                    head1 = head1->next;
                    fchar = fgetc(file);
                }
                if (fchar == EOF) {
                    Students[studentCounter] = head;
                    Students[studentCounter + 1] = NULL;
                    fchar = fgetc(file);
                    Student = (node *) malloc(sizeof(node));
                    head = Student;
                    head1 = head;
                    studentCounter++;
                }
                switchNY = 0;
            }
        }else if(fchar == '\n'){
            Students[studentCounter] = head;
            Students[studentCounter+1] = NULL;
            fchar = fgetc(file);
            Student = (node *)  malloc(sizeof(node));
            head = Student;
            head1 = head;
            studentCounter++;
        }else if(fchar == ';'){
            head1->year = (int) NULL;
            if(switchNY == 1){
                head1->name = fchar;
            }
            switchNY = 1;
            fchar = fgetc(file);
            head1->next = malloc(sizeof(node*));
            head1 = head1->next;
        }
    }
    fclose(file);

    sortAndPrintByBirth(Students);
    //sortAndPrintByFaculty(Students);

    return -1;
}

int isLetter(char character) {
    return ((character >= 'a' && character <= 'z') || (character >= 'A' && character <= 'Z') || (character == ' '));
}
int isNumber(char character) {
    return (character >= '0' && character <= '9');
}
int charToInt(char character) {
    if (character >= '0' && character <= '9') {
        return character - '0';
    } else {
        return -1;
    }
}

node** sortAndPrintByBirth(node* *list) {
    int i = length(list);
    node* result[i];

    for(int a=0; a<i; a++){
        result[a] = list[a]->number;
    }

    for(int count = 0; count < i-1; count++){
        for(int step = 0; step < i-1 ; step++){
            node *iter1;
            node *iter2;
            iter1 = result[step];
            iter2 = result[step+1];
            int year1 = 0,year2 = 0;
            while (iter2 != NULL){
                while ((void *) iter1->next->year == NULL) {
                    iter1 = iter1->next;
                }
                while ((void *) iter2->next->year == NULL) {
                    iter2 = iter2->next;
                }
                for (int j = 0; j < 4; ++j) {
                    iter1 = iter1->next;
                    year1 = 10 * year1 + iter1->year;
                }

                for (int j = 0; j < 4; ++j) {
                    iter2 = iter2->next;
                    year2 = 10 * year2 + iter2->year;
                }
                break;
            }
            if(year1 < year2){
                node* temp;
                temp = result[step];
                result[step] = result[step+1];
                result[step+1] = temp;
            }else if(year2 == year1){
                continue;
            }
        }
    }
    node* iter3;
    printf("Student names in ascending order by birthday:\n");
    for (int j = 0; j < i; ++j) {
        iter3 = result[j]->next;
        while(iter3->year == (int )NULL){
            printf("%c",iter3->name);
            iter3 = iter3->next;
        }
        for (int k = 0; k < 4; ++k) {
            printf("%d",iter3->year);
            iter3 = iter3->next;
        }
        printf("\n");
    }
    return result;
}

node** sortAndPrintByFaculty(node* *list){
    int i = length(list);
    node* result[i];
    char* temp[i];

    for(int a=0; a<i; a++){
        temp[a] = list[a]->number;
    }

    for(int count = 0; count < i-1; count++){
        for(int step = 0; step < i-1 ; step++){
            for(int digit = 0; digit < 3 ; digit ++){
                if(charToInt(temp[step][digit]) < charToInt(temp[step+1][digit])){
                    char* c;
                    c = temp[step];
                    temp[step] = temp[step+1];
                    temp[step+1] = c;
                    break;
                }else if(charToInt(temp[step][digit]) == charToInt(temp[step+1][digit])){
                    continue;
                }else{
                    break;
                }
            }
        }
    }

    for (int j = 0; j < i; ++j) {
        push(temp[j]);
    }
    printf("School numbers by the faculty codes in ascending order:\n");
    for (int j = 0; j < i; ++j) {
        printf("%s\n", pop());
    }

    return result;
}

int length(node** list){
    int value = 0;
    while(list[value] != NULL){
        value++;
    }
    return value;
}

void push(char* value)  {
    struct s_node *m;
    m=(struct s_node*)malloc(sizeof(struct s_node ));
    m->number= value ;
    m->next=stack;
    stack=m;
}
void display()  {
    struct s_node *temp=stack;
    while(temp!=NULL)   {
        printf("%s\t", temp->number);
        temp=temp->next;
    }
}

char* pop()  {
    struct s_node *temp ;
    if (stack == NULL) {
        printf("\nSTACK is Empty.");
    } else {
        char* i = stack->number;

        temp = stack;
        stack = stack->next;
        free(temp);
        return i;

    }
    return NULL;
}

问题分析与修复 #

1. 核心错误：指针类型不匹配与非法内存访问 #

sortAndPrintByBirth函数中，result[a] = list[a]->number;存在致命问题：

• list[a]是node*类型，list[a]->number是char[9]数组，会被隐式转为char*指针
• result是node*数组，将char*赋值给node*导致类型完全不匹配，后续把字符串地址当成链表节点地址访问，读取的内容完全不符合预期，引发乱码。

修复：
将result数组改为直接存储节点指针：

for(int a=0; a<i; a++){
    result[a] = list[a];
}

2. 链表节点内存分配错误 #

原代码中head1->next = malloc(sizeof(node*));分配的是指针大小的内存，而非node结构体的完整大小，导致内存不足，访问结构体成员时越界。

修复：
改为分配结构体大小的内存：

head1->next = malloc(sizeof(node));

3. 年份读取逻辑冗余且易出错 #

原代码将年份的每个数字单独存入一个节点的year字段，后续需要遍历4个节点拼接年份，逻辑复杂且容易出错。

修复：
读取时直接拼接为完整年份值存入单个节点：

else if(isNumber(fchar)){
    if(switchNY == 0){
        // 学号读取逻辑不变
    }else {
        int year = 0;
        for (int i = 0; i < 4; i++) {
            year = year * 10 + charToInt(fchar);
            fchar = fgetc(file);
        }
        head1->year = year;
        head1->next = malloc(sizeof(node));
        head1 = head1->next;
        switchNY = 0;
    }
}

4. 无效的NULL赋值 #

head1->year = (int) NULL;是错误用法，NULL是指针类型，强制转为int会得到平台相关值，无法作为有效标记。

修复：
用特殊值（如-1）标记未初始化的年份：

head1->year = -1;

5. 文件路径转义错误 #

原文件路径中的反斜杠未转义，会被解析为转义字符，导致文件无法打开。

修复：
转义路径中的反斜杠：

file = fopen("C:\\Users\\PC\\CLionProjects\\untitled1\\input.txt", "r");

内容的提问来源于stack exchange，提问作者çağatay dişli