C代碼可在linux（geany）上運行，但不能在Windows（VS2008）上運行

Question

我已經為一個程序編寫了代碼，在該程序中，用戶輸入.txt文件的名稱，並且該程序打印文件中找到的字母數字單詞或數字（字母數字單詞以字母開頭，包括字母或數字）。 無論如何，當在使用Geany的Linux上運行時，它可以正常工作，但在Visual Studio 2008上卻不能（我使用此視頻允許VS2008編譯C代碼）。

確切的問題是它顯示的字母數字就像表情符號。 我相信還有一個無限循環，可能與我對fseek函數的使用有關。

#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-您已將指針分配給本地數組sem-> s = lexeme; 在yylex（）內部。 因此，當調用返回到main時，lexeme中的值將變為無效。 因此，您必須分配內存，然后將值從lexeme復制到sem->。 按照代碼中的// change注釋查看更改：

#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' );
}