Address 0x1B91D1C0 is 0 bytes after a block of size 8 alloc'd

t = (char*) malloc((n)*sizeof(char));

hi,
this is what i have .. and the error happens when i do

printf("T %s\n",t);

so, i changed it to this:

t=(char*)malloc((n+10)*sizeof(char));
printf("T %s\n",t);

then i got the error for Conditional jump or move depends on uninitialised value(s)
...but i know it is initialised..

Ok,

What's the value of 'n'?

Note that when you call printf(), t IS uninitialized.  You've allocated memory, but not copied any value to *t*.


Kent

sorry, i had to rewrite everything since i cant copy paste from the terminal

n= ftell(fp);

t = (char*) malloc((n+1)*sizeof(char));
rewind(fp);

fread(t, sizeof(t[0]), n, fp);

fclose(fp)
printf("T %s\n",t);

thanks a million.

n= ftell(fp);

t = (char*) malloc((n+1)*sizeof(char));
rewind(fp);

fread(t, sizeof(t[0]), n, fp);
fclose(fp);
t[n] = '\0';

printf("T %s\n",t);

So you have:
t = (char*) malloc(n+1);
memset(t, 0, n + 1);
fread(t, 1, n, fp);
and it still does not work?
Please check. You will read only 1 byte.

hi pgnatyuk,

isn't t = (char*) malloc((n+1)*sizeof(char)); instead of

t= (char*) malloc(n+1);

sizeof(char) is 1 byte. So it does not matter if it is n + 1 or (n + 1) * sizeof(char)

i am rewriting the small program instead of commenting it out... pls give me 5 minutes...thanks..

int
main(int argc,char *argv[])
{

        FILE *fp=NULL;
        fp = fopen("ban.txt","rb");
        if(fp ==NULL)
                fprintf(stderr,"Error opening file\n");

        n=ftell(fp);
        t=(char *)malloc((n+1));
        memset(t,0,n+1);
        rewind(fp);

        fread(t,1,n,fp);
        fclose(fp);
        t[n]='\0';
        printf("t is %s\n",t);
        free(t);

        return 0;
}
             
Nothing gets printed out...i even added rewind(fp)

i am adding fseek...just one second..

can you try this one,
#include <stdio.h>
#include <stdlib.h>
int main()
{
    FILE *fp;
    int n;
    char *t;
    //open file to read something in binary mode
    fp=fopen("C:/FileDirectory/file.txt","rb");
    if (fp==NULL)
    {
        perror("Can not open file");
    }
    fseek(fp,0,SEEK_END);
    n= ftell(fp); //get the file size
    //allocate necessary memory
    t = (char*) malloc((n+1)*sizeof(char));
    //go to the beginning of the file
    fseek(fp,0,SEEK_SET);
    //read the contents into memory
    fread(t, sizeof(char), n, fp);
    //close the file
    fclose(fp);
    t[n] = '\0';
    printf("T %s\n",t);
    free(t);//free the memory to avoid memory leak
    return 1;
}

I'm testing. You forgot return if the file is not found.
if (fp==NULL)
{
      perror("Can not open file");
      return 0;
}

this code below works.

No problem with ANSI text file.

From the binary file it reads, but printf can show only null-terminated strings. I put an executable and see only the file signature.

#include <stdio.h>
#include <stdlib.h>
 
int main()
{
	FILE *fp = NULL;
	int n = 0;
	char *t = NULL;
 
	//open file to read something in binary mode
	fp = fopen("C:/test.txt", "rb");
	if (fp==NULL)
	{
		perror("Can not open file");
		return 0;
	}
 
	fseek(fp, 0, SEEK_END);
	n= ftell(fp); //get the file size
 
	//allocate necessary memory
	t = (char*) malloc((n+1)*sizeof(char));
 
	//go to the beginning of the file
	fseek(fp,0,SEEK_SET);
 
	//read the contents into memory
	fread(t, sizeof(char), n, fp);
 
	//close the file
	fclose(fp);
 
	t[n] = '\0';
	printf("T %s\n",t);
	free(t);//free the memory to avoid memory leak
	return 1;
}
                                              

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so you need to read a binary data and print it on the screen?

thanks

you are welcome

hi,

i just realised that more posts were posted when i was trying out..thanks a lot for all the help...

@pgnatyuk:
You took my example code (it is quick fix to the problem) and posted without mentioning anything?.

Why?
You mean I couldn't post it?
I added few comments. Something happens with your server again?
I wrote that you didn't handle the situation, when the file was not found (actually, when fopen failed). The second comment was that you read a binary file and try to print it with printf as a string. So you will see the data if there is no 0. The binary data, if it is going to be printed should be converted into a hexadecimal format. And proposed you my assistance. :)

@pgnatyuk:
I am not asker.Asker here is zizi21.Iam posted only my suggestion.