Question

我为一个程序编写了代码，用户输入了.txt文件的名称，程序打印出文件中的字母数字或数字（字母数字单词以字母开头，包括字母或数字）。无论如何，当使用Geany在Linux上运行时，它工作正常，但在Visual Studio 2008上却没有（我使用this video来允许VS2008编译c代码）。

确切的问题是它显示的字母数字就像表情符号。还有一个无限循环，我认为可能与我使用fseek函数有关。

#include <stdio.h>
#include <ctype.h>
#include <string.h>

union semantic_info
{
    char *s;
    int i;
}SEMANTIC_INFO ;

int yylex(FILE *fp, union semantic_info *sem);
void WaitForEnter(void);

int main()
{
    union semantic_info *ptrs;
    char filename[20];
    int a=0,n=0;
    int k;
    FILE *fp;
    ptrs = &SEMANTIC_INFO;
    printf("Hey you, give me a file name: \n");
    scanf("%s", filename);
    fp = fopen(filename, "r");
    do
    {   
        k = yylex(fp, ptrs);
        if( k==1 )
        {
            printf("%s%s\n", "The type is alphanumeric and it's the: ", SEMANTIC_INFO.s);
            a++;
        }
        else if( k==2 )
        {
             printf("%s%d\n", "The type is arithmetic and it's the: ", SEMANTIC_INFO.i);
             n++;
        }
    }while( k!=0 );
    printf("we found %d alphanumerics and %d numbers! \n", a, n);
    return 0;
}


int yylex(FILE *fp, union semantic_info *sem)
{
    int nextcharacter;
    char lexeme[100]="";
    int k=1, i=0, r=3;
    nextcharacter = fgetc(fp);
    if ( nextcharacter == EOF)
    {
        r=0;
    }
    else if ( isalpha(nextcharacter) != 0 )
    {
        lexeme[i] = (char)nextcharacter;
        //printf("at position %d there is %c \n", i, lexeme[i]);
        while(k==1)
        {
            nextcharacter = fgetc(fp);
            if(isalnum(nextcharacter) != 0 )
            {
                i++;
                lexeme[i] = (char)nextcharacter;
                //printf("at position %d there is %c \n", i, lexeme[i]);
            }
            else
            {
                lexeme[i+1] = '\0';
                k=0;
                sem->s = lexeme;
                r=1;
                fseek(fp, -1, SEEK_CUR);
            }
        }
    }
    else if ( isdigit(nextcharacter) != 0 )
    {
        lexeme[i] = (char)nextcharacter;
        //printf("at position %d there is %c \n", i, lexeme[i]);
        while(k==1)
        {
            nextcharacter = fgetc(fp);
            if(isdigit(nextcharacter)!= 0 )
            {
                i++;
                lexeme[i] = (char)nextcharacter;
                //printf("at position %d there is %c \n", i, lexeme[i]);
            }
            else
            {
                lexeme[i+1] = '\0';
                k=0;
                sscanf(lexeme, "%d", &sem->i);
                r=2;
                fseek(fp, -1, SEEK_CUR);
            }
        }
    }
    WaitForEnter();
    return r;
}   

void WaitForEnter(void)
{
printf("Press Enter to continue: ");
//fflush(stdout);
while ( getchar() != '\n' )
;
}

Answer 1

Visual Studio版本 - 您已将指针指定为本地数组sem-＆gt; s = lexeme;在yylex（）里面。因此，当调用返回main时，lexeme中的值变为void。所以，你必须分配内存，然后将值从lexeme复制到sem-＆gt;。按照代码中的//更改注释查看更改：

#include <stdio.h>
#include <ctype.h>
#include <string.h>
#include<malloc.h>//change

union semantic_info{
    char *s;
    int i;
}SEMANTIC_INFO ;

int yylex(FILE *fp, union semantic_info *sem);
void WaitForEnter(void);


int main()
{
union semantic_info *ptrs;
char filename[20];
int a=0,n=0;
int k;

FILE *fp;
ptrs = &SEMANTIC_INFO;
printf("Hey you, give me a file name: \n");
scanf("%s", filename);
fp = fopen(filename, "r");
do
{   
    k = yylex(fp, ptrs);
    if( k==1 )
    {
        printf("%s%s\n", "The type is alphanumeric and it's the: ", SEMANTIC_INFO.s);
        a++;
    }
    else if( k==2 )
    {

         printf("%s%d\n", "The type is arithmetic and it's the: ", SEMANTIC_INFO.i);
         n++;
    }
}while( k!=0 );
printf("we found %d alphanumerics and %d numbers! \n", a, n);
return 0;
}


int yylex(FILE *fp, union semantic_info *sem)
{
int nextcharacter;
char lexeme[100]="";
int k=1, i=0, r=3;
nextcharacter = fgetc(fp);
if ( nextcharacter == EOF)
{
    r=0;
}
else if ( isalpha(nextcharacter) != 0 )
{
    lexeme[i] = (char)nextcharacter;
    //printf("at position %d there is %c \n", i, lexeme[i]);
    while(k==1)
    {
        nextcharacter = fgetc(fp);
        if(isalnum(nextcharacter) != 0 )
        {
            i++;
            lexeme[i] = (char)nextcharacter;
            //printf("at position %d there is %c \n", i, lexeme[i]);
        }
        else
        {
            lexeme[i+1] = '\0';
            k=0;
            sem->s=(char *)malloc(sizeof(char)*(i+2));//change
            memcpy(sem->s,lexeme, i+2);//change
            //sem->s = lexeme;//change 

            r=1;
            fseek(fp, -1, SEEK_CUR);
        }
    }
}
else if ( isdigit(nextcharacter) != 0 )
{
    lexeme[i] = (char)nextcharacter;
    //printf("at position %d there is %c \n", i, lexeme[i]);
    while(k==1)
    {
        nextcharacter = fgetc(fp);
        if(isdigit(nextcharacter)!= 0 )
        {
            i++;
            lexeme[i] = (char)nextcharacter;
            //printf("at position %d there is %c \n", i, lexeme[i]);
        }
        else
        {
            lexeme[i+1] = '\0';
            k=0;
            sscanf(lexeme, "%d", &sem->i);
            r=2;
            fseek(fp, -1, SEEK_CUR);
        }
    }
}
WaitForEnter();
return r;
}   

void WaitForEnter(void){
printf("Press Enter to continue: ");
//fflush(stdout);
while ( getchar() != '\n' );
}

C代码适用于linux（geany）但不适用于Windows（VS2008）

1 个答案: