Thread: gcc compiler warning

I wrote a wrapper function to either read or write to a file stream based on the 'flag' argument passed to the function:

Code:

FILE *openfile(char *filename, char flag) {
	FILE *fin = NULL, *fout = NULL;
	
	if (flag == 'd') {
		fin = fopen(filename, "r");
		if (fin == NULL) {
			fprintf(stderr, "Error: Unable to open %s\n", filename);
			exit(EXIT_FAILURE);
		}
		
		return fin;
	}
	else if (flag == 'e') {
		fout = fopen(filename, "w");
		if (fout == NULL) {
			fprintf(stderr, "Error: Unable to create %s\n", filename);
			exit(EXIT_FAILURE);
		}
		
		return fout;
	}
}

When I compile the program, I am getting a warning:

dna1.c:150: warning: control reaches end of non-void function

I understand the warning. It's being thrown because it doesn't think I'm returning a file pointer. The thing is I am returning a file pointer based on a condition. Is this normal? The program works fine....but I was wondering if there is anything I could do with the code to get rid of the warning.

Thanks!

What does openfile return if flag is not 'd' or 'e'?

It's because if flag is neither d nor e, your function is not returning anything as it should.

Code:

FILE *openfile(char *filename, char flag) {
	FILE *fin = NULL, *fout = NULL;
	
	if (flag == 'd') {
	     ...
		return fin;
	}
	else if (flag == 'e') {
	    ...
		return fout;
	}
        return NULL;             // invalid option return NULL
      // or use else return NULL;
}

Thanks Bayint Naung,

I edited my previous post at the same time you replied. That seems to have done it. Thanks again!