Stupid segfault

[ctnorman]

Hello, I'm currently doing a project that requires the user to run a program with a source file name and destination file name as parameters. The program then encrypts the text from the source file and puts it into the destination file using a simple substitution cipher. The program reads in a character from the source, puts it into a method that returns the encrypted character, and then is supposed to write the encrypted character into the file. When I try to write the character into the file, I get a segfault. I've tried just about everything to try and fix this. I have a feeling it's right under my nose. Anyways, here's my routine that encrypts everything:

void encrypt_file(CIPHER * cipher_key, FILE * src_file, FILE * dest_file){
	char encrypted_char;

	while((encrypted_char = get_encrypted_char(cipher_key, fgetc(src_file))) != EOF){
		//printf("%c", encrypted_char);
		fputc(encrypted_char, dest_file);
	}
	
	fclose(src_file);
	fclose(dest_file);
}

and here's the get_encrypted_char method:

char get_encrypted_char(CIPHER * cipher_key, char char_to_encrypt){
	int i;
	char encrypted_char;
	encrypted_char = char_to_encrypt;
	for (i = 0; i < CIPHER_LENGTH; i++){
		if(char_to_encrypt == cipher_key->plaintext[i]){
			encrypted_char = cipher_key->ciphertext[i];
		}
	}
	return encrypted_char;

}

the CIPHER is a struct that encapsulates a plaintext character array along with a ciphertext character array such that their indices match. Any insight on this would be greatly appreciated.

[Adak]

When the function returns with the encrypted char, can you print it and see that it's ok?

It looks like you're trying to return a variable that has gone out of scope. Dodgy imo.

[ctnorman]

When the function returns with the encrypted char, can you print it and see that it's ok?

It looks like you're trying to return a variable that has gone out of scope. Dodgy imo.

Yes. The encrypted chars print fine.

[tabstop]

I suppose a silliness check -- if printing to the screen works, and the file doesn't, then is the file (a) opened (b) successfully (c) for output?

[ctnorman]

I suppose a silliness check -- if printing to the screen works, and the file doesn't, then is the file (a) opened (b) successfully (c) for output?

Yes, I have the following code to open the destination file:

dest_file = fopen(argv[2], "w+");
		
if(dest_file = NULL){
	printf("Error opening destination file.\n");
}

else{
	printf("Loaded destination file successfully.\n");
}

When I run the program, it prints that it opened the file successfully.

[vart]

fgetc returns int so you could distinguish EOF from other chars
you are passing EOF as char into get_encrypted_char loosing this info, so how do you plan to exit the loop?

[Salem]

> if(dest_file = NULL)
Yes, and == would be so much better....