Passing argument 2,3 makes pointer from integer without a cast

Question

Using the language C and Netbeans 8.0.2 I'm trying to read a set of characters, of two files and pass those characters to a method called Patmat which is used to compare them.

The Patmat method has three arguments.The int argument is the number of mismatches that could have and other two character arguments are the file contents.

Below is the Patmat method which I got from an article and there is a long process inside it to compare.

int Patmat(int k, char *pattern, char *text){
}

Here is my main method

int main() {   
    FILE *fp1;
    FILE *fp2;

    char c;
    char c2;

    fp1= fopen ("file1.txt","r");
    fp2= fopen("file2.txt","r");

    while(1)
    {
        c = fgetc(fp1);
        if(c==EOF)
            break;
        else
            printf("%c", c); 
    }

    while(1)
    {
        c2 = fgetc(fp2);
        if(c2==EOF)
            break;
        else
            printf("%c", c2); 
    }
    fclose(fp1);
    fclose(fp2); 
    **// Patmat(0,&c,&c2);
    Patmat(0,c,c2);**
    return 0;   
}

As i'm not much familiar with C and pointers can anyone help me to pass those character sets of two files to the Patmat method? It does not work as above.

The content of two files are :

file1.txt: AGGTACCGTA
file2.txt: AGGTACCGTA

I directly passed those arguments as Patmat(0,"AGGTACCGTA","AGGTACCGTA"). It worked fine and returned the answer as 1 which is correct.

But now I want to read those character sets from a file and pass them to the Patmat method. It gives the following warning:

warning: passing argument 3 of 'Patmat' makes pointer from integer without a cast
 warning: passing argument 2 of 'Patmat' makes pointer from integer without a cast

Thanks in advance and sorry if I made any inconvenience. This is my first attempt to post a question here.

Run the code in a debugger and trace it line by line inspecting the relevant variable. On how to do this reading this ericlippert.com/2014/03/05/how-to-debug-small-programs might get you started. — alk
c and c2 aren't character sets, they're single characters. — melpomene
Thanks, but what i'm saying is all the characters in the file1.txt are assigned to the variable c as c= 'AGGTACCGTA' and characters in the file2.txt are assigned to the variable c2 as c2='AGGTACCGTA'. Thats why I refferred them as character set. Sorry if i done a mistake. It prints nicely c and c2 but i can't pass them to the method. Would it be possible to use & sign as Patmat(0,&c,&c2). But it did not work. Thank you — asw
@asw: A char variable is a single byte, it can only contain single character. — Blastfurnace

Yorick de Wid Yorick de Wid · Accepted Answer · 2015-09-20T11:22:22

If you want to read the entire file a char (one character) is not what you want. In that case you want to read the contents of the files into an array.

char *buffer[1024]; // for example
int result = fread(buffer, 1, 1024, fp1);

Now buffer contains your file contents which can be passed to your Patmat function

Patmat(0, buffer, buffer2); // buffer2 goes the same way

If you want to read the whole file in once (useful for smaller files) you can also allocate buffer dynamically. Also make sure to set the null terminator.

Update: an example would be:

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

#define BUFSZ 32

void patmat(int k, char *pattern, char *text) {
    /* Compare or do something here */
    printf("K %d\nPattern %s\nText %s\n", k, pattern, text);
}

int main(int argc, char *agrv[]) {
    FILE *fp1 = NULL;
    FILE *fp2 = NULL;

    char buffer[BUFSZ];
    char buffer2[BUFSZ];

    if (!(fp1 = fopen("file1.txt","r"))) {
        perror("open file");
        return 1;
    }
    if (!(fp2 = fopen("file2.txt","r"))) {
        perror("open file");
        return 1;
    }

    size_t result = fread(buffer, 1, BUFSZ, fp1);
    if (!result)
        puts("reading error");

    size_t result2 = fread(buffer2, 1, BUFSZ, fp2);
    if (!result)
        puts("reading error");

    buffer[result-1] = '\0';
    buffer2[result2-1] = '\0';

    patmat(0, buffer, buffer2);

    fclose(fp1);
    fclose(fp2);
    return 0;
}

This is just an example, there are other/better ways.

Passing argument 2,3 makes pointer from integer without a cast

2 Answers