C语言集合程序打印笑脸而非字符问题求助

现象 #

用布尔数组实现集合操作的C语言函数，运行时出现以下异常：

• O之前的字母显示为笑脸（随机乱码），O之后显示正常
• 打印集合并集时所有字母均显示为笑脸
• 尝试调换A和O的位置、改用{'A','B',...}形式定义字符数组，问题仍存在

完整代码 #

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

#define megisto_plithos 26

typedef bool typos_synolou[megisto_plithos];
typedef int stoixeio_synolou;

void Dimiourgia(typos_synolou synolo);
void Katholiko(typos_synolou synolo);
void Eisagogi(stoixeio_synolou stoixeio, typos_synolou synolo);
bool Melos(stoixeio_synolou stoixeio, typos_synolou synolo);
bool IsaSynola(typos_synolou s1, typos_synolou s2);
bool Yposynolo(typos_synolou s1, typos_synolou s2);
void EnosiSynolou(typos_synolou s1, typos_synolou s2, typos_synolou enosi);
void TomiSynolou(typos_synolou s1, typos_synolou s2, typos_synolou tomi);
void DiaforaSynolou(typos_synolou s1, typos_synolou s2, typos_synolou diafora);
void EmfanisiSynolou(typos_synolou synolo, char letters[]);

int main()
{
    char letters[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";

    typos_synolou agglika_kefalaia[megisto_plithos];
    Dimiourgia(agglika_kefalaia[megisto_plithos]);
    Katholiko(agglika_kefalaia[megisto_plithos]);
    EmfanisiSynolou(agglika_kefalaia[megisto_plithos], letters);
    typos_synolou S[megisto_plithos], T[megisto_plithos];
    Dimiourgia(S[megisto_plithos]);
    Dimiourgia(T[megisto_plithos]);
    Eisagogi(0, S[megisto_plithos]);
    Eisagogi(1, S[megisto_plithos]);
    Eisagogi(2, S[megisto_plithos]);
    Eisagogi(3, S[megisto_plithos]);
    Eisagogi(0, T[megisto_plithos]);
    Eisagogi(2, T[megisto_plithos]);
    Eisagogi(4, T[megisto_plithos]);
    Eisagogi(6, T[megisto_plithos]);
    Eisagogi(8, T[megisto_plithos]);
    printf("\n");
    EmfanisiSynolou(S[megisto_plithos], letters);
    printf("\n");
    EmfanisiSynolou(T[megisto_plithos], letters);
    printf("\n");
    if(IsaSynola(S[megisto_plithos], T[megisto_plithos]))
    {
        printf("ISA SYNOLA");
    }
    else printf("NOT ISA SYNOLA");
    printf("\n");
    if(Yposynolo(S[megisto_plithos], T[megisto_plithos]))
    {
        printf("S YPOSYNOLO T");
    }
    else printf("NOT S YPOSYNOLO T");
    printf("\n");
    if(Yposynolo(T[megisto_plithos], S[megisto_plithos]))
    {
        printf("T YPOSYNOLO S");
    }
    else printf("NOT T YPOSYNOLO S");
    typos_synolou enosi[megisto_plithos];
    printf("\n");
    EnosiSynolou(S[megisto_plithos], T[megisto_plithos], enosi[megisto_plithos]);
    EmfanisiSynolou(enosi[megisto_plithos], letters);
    printf("\n");
    typos_synolou tomi[megisto_plithos];
    TomiSynolou(S[megisto_plithos], T[megisto_plithos], tomi[megisto_plithos]);
    EmfanisiSynolou(tomi[megisto_plithos], letters);
    printf("\n");
    typos_synolou diafora[megisto_plithos];
    DiaforaSynolou(S[megisto_plithos], T[megisto_plithos], diafora[megisto_plithos]);
    EmfanisiSynolou(diafora[megisto_plithos], letters);
    return 0;
}

void Dimiourgia(typos_synolou synolo)
{
    stoixeio_synolou i;

    for (i = 0; i < megisto_plithos; i++)
        synolo[i] = false;
}

void Katholiko(typos_synolou synolo)
{
    stoixeio_synolou i;

    for (i = 0; i < megisto_plithos; i++)
        synolo[i] = true;
}

void Eisagogi(stoixeio_synolou stoixeio, typos_synolou synolo)
{
    synolo[stoixeio] = true;
}

bool Melos(stoixeio_synolou stoixeio, typos_synolou synolo)
{
    return synolo[stoixeio];
}

bool IsaSynola(typos_synolou s1, typos_synolou s2)
{
    stoixeio_synolou i;
    bool isa;

    isa = true;
    i=0;
    while (i < megisto_plithos && isa)
        if (Melos(i,s1) != Melos(i,s2))
            isa = false;
        else
            i++;
    return isa;
}

bool Yposynolo(typos_synolou s1, typos_synolou s2)
{
    stoixeio_synolou i;
    bool yposyn;

    yposyn = true;
    i=0;
    while (i < megisto_plithos && yposyn)
        if (Melos(i, s1) && !Melos(i, s2))
            yposyn = false;
        else
            i++;
    return yposyn;
}

void EnosiSynolou(typos_synolou s1, typos_synolou s2, typos_synolou enosi)
{
    stoixeio_synolou i;

    for (i = 0; i < megisto_plithos; i++)
        enosi[i] = Melos(i, s1) || Melos(i, s2);
}

void TomiSynolou(typos_synolou s1, typos_synolou s2, typos_synolou tomi)
{
    stoixeio_synolou i;

    for (i = 0; i < megisto_plithos; i++)
        tomi[i] = Melos(i, s1) && Melos(i, s2);
}

void DiaforaSynolou(typos_synolou s1, typos_synolou s2, typos_synolou diafora)
{
    stoixeio_synolou i;

    for (i = 0; i < megisto_plithos; i++)
        diafora[i] = Melos(i, s1) && (!Melos(i, s2));
}

void EmfanisiSynolou(typos_synolou synolo, char letters[megisto_plithos])
{
    int i;
    for(i = 0; i < megisto_plithos; i++)
    {
        if(synolo[i] == true)
        {
            printf("%c ", letters[i]);
        }
    }
}

问题原因 #

核心错误是集合变量的声明和参数传递完全错误：

1. 类型定义误解：typedef bool typos_synolou[megisto_plithos]; 已经将typos_synolou定义为一个包含26个bool的数组类型，声明单个集合时直接写typos_synolou 变量名;即可，不需要再加[megisto_plithos]——否则会变成包含26个集合的二维数组（26*26个bool）。
2. 越界访问内存：比如Dimiourgia(agglika_kefalaia[megisto_plithos]); 中，agglika_kefalaia[megisto_plithos]是访问二维数组的第27个元素（索引从0开始），属于严重越界，会破坏内存中其他变量（比如letters数组）的内容，这就是乱码的根源。
3. 前14个字符异常是内存布局巧合：越界操作刚好覆盖了letters数组的前半部分，O是第15个字符（索引14），因此之后的字符未被影响。

修正方案 #

修改main函数中所有集合变量的声明和传递方式：

• 将typos_synolou agglika_kefalaia[megisto_plithos]; 改为 typos_synolou agglika_kefalaia;
• 将Dimiourgia(agglika_kefalaia[megisto_plithos]); 改为 Dimiourgia(agglika_kefalaia);
• 同理，typos_synolou S[megisto_plithos], T[megisto_plithos]; 改为 typos_synolou S, T;
• 所有传递这些变量的函数调用，都去掉[megisto_plithos]，比如Eisagogi(0, S);、EmfanisiSynolou(S, letters);等
• 集合运算的结果变量（enosi、tomi、diafora）也做同样修改

修正后的main函数 #

int main()
{
    char letters[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";

    typos_synolou agglika_kefalaia;
    Dimiourgia(agglika_kefalaia);
    Katholiko(agglika_kefalaia);
    EmfanisiSynolou(agglika_kefalaia, letters);
    typos_synolou S, T;
    Dimiourgia(S);
    Dimiourgia(T);
    Eisagogi(0, S);
    Eisagogi(1, S);
    Eisagogi(2, S);
    Eisagogi(3, S);
    Eisagogi(0, T);
    Eisagogi(2, T);
    Eisagogi(4, T);
    Eisagogi(6, T);
    Eisagogi(8, T);
    printf("\n");
    EmfanisiSynolou(S, letters);
    printf("\n");
    EmfanisiSynolou(T, letters);
    printf("\n");
    if(IsaSynola(S, T))
    {
        printf("ISA SYNOLA");
    }
    else printf("NOT ISA SYNOLA");
    printf("\n");
    if(Yposynolo(S, T))
    {
        printf("S YPOSYNOLO T");
    }
    else printf("NOT S YPOSYNOLO T");
    printf("\n");
    if(Yposynolo(T, S))
    {
        printf("T YPOSYNOLO S");
    }
    else printf("NOT T YPOSYNOLO S");
    typos_synolou enosi;
    printf("\n");
    EnosiSynolou(S, T, enosi);
    EmfanisiSynolou(enosi, letters);
    printf("\n");
    typos_synolou tomi;
    TomiSynolou(S, T, tomi);
    EmfanisiSynolou(tomi, letters);
    printf("\n");
    typos_synolou diafora;
    DiaforaSynolou(S, T, diafora);
    EmfanisiSynolou(diafora, letters);
    return 0;
}

内容的提问来源于stack exchange，提问作者Shady Sheen