Question

I need a brief text file to explain why the program “filesize1v.c” gets stuck in the “do/while” loop (i.e., explain why “ch != EOF” is always true) ??

example.txt :

hello
ÿhello everyone.

_________________

//filesize1v.c
#include 
#include 

int main(int argc, char *argv[]){  
        FILE *fd;
        
        unsigned char ch;  //what will happen if you uncomment this line and comment the                //next line
        //char ch;

        int fileSize=-1;

        fd = fopen(argv[1], "r"); 

        do{
                ch=getc(fd);  //0xFF
                fileSize++;
                printf("fileSize=%d\n", fileSize);
                printf("Char read is ch=%c, in hex ch=%#hhx EOF is %#x\n\n", ch, ch, EOF);
                sleep(1);
        } while( ch != EOF);  //ch =0x FF,  EOF=0x FFFF FFFF
        
        printf(" \nout of do while loop now.\n\n");
        printf("ch=%d EOF=%#x\n", ch, EOF);
        printf("size of char =%ld size of EOF=%ld\n", sizeof(char), sizeof(EOF));
        
        printf("Size of %s is %d\n", argv[1], fileSize);
}


//suggeson: levae all the printf statment in place
//run the code to observe the output
//then use gdb to find out the "bug"

Answer 1

//filesize1v.c
#include 
#include 


int main(int argc, char *argv[]){  
        FILE *fd;
        
        //unsigned char ch;  //what will happen if you uncomment this line and comment the                //next line
        char ch;

        int fileSize=-1;

        fd = fopen(argv[1], "r"); 

        do{
                ch=getc(fd);  //0xFF
                fileSize++;
                printf("fileSize=%d\n", fileSize);
                printf("Char read is ch=%c, in hex ch=%#hhx EOF is %#x\n\n", ch, ch, EOF);
                sleep(1);
        } while( ch != EOF);  //ch =0x FF,  EOF=0x FFFF FFFF
        
        printf(" \nout of do while loop now.\n\n");
        printf("ch=%d EOF=%#x\n", ch, EOF);
        printf("size of char =%ld size of EOF=%ld\n", sizeof(char), sizeof(EOF));
        
        printf("Size of %s is %d\n", argv[1], fileSize);
}


//suggeson: levae all the printf statment in place
//run the code to observe the output
//then use gdb to find out the "bug"

You are getting this error and stuck on the do/while loop becuase in the code we are using the unsigned char and the EOF is a signed int quantity , so these value can never be equal in any case, so the code is goin in the infinite loop , you need to declare the ch as the int so that these values can be compared, so unsigned char ch , can only contain the number or the magnitude without any sign in front and the EOF is defined as -1 in the stdio.h and the other programming langugaes as well , so , the values when compared will always give True as a result because they are not eqaul , so declare the ch as signed int.