Thread: Segmentation Fault

Line 57 ... you need to make storage for the strings ... char s[150]; ... adjust as needed.
Line 65 ... No & in front of the s parameter.

By the way... all you're doing is line counting... I hope that's what you intended.

Yes it is. On line 65 what do you mean - I should do while ( fgets(&s&, 150, stream) ) ?

Originally Posted by Kalastrian

Yes it is. On line 65 what do you mean - I should do while ( fgets(&s&, 150, stream) ) ?

fgets - C++ Reference

I am thinking he wants you to use an character array (or char pointer) instead of a single char.

If you use an char pointer; you need to allocate space for it!

Tim S.

Once you make s a char array, like char s[150]; then you want to remove the & from line 65. & gives you the address of something. But when you use the name of an array by itself, without any [ ], C gives you the address of the first element, which is exactly what fgets wants, so it should look like:

Code:

char s[150];
...
fgets(s, sizeof(s), stream);

Note, I use sizeof(s) so that if you change the size of the buffer (array), you only need to change it in one place.

Thanks for the replies.
Also, I'm sorry but English isn't my native language, so... Sorry if I'm a little daft.

I've made the changes you've recommended, made s a character array by s[150] and removed the & from the fgets.
After compiling, I still get the segmentation fault.


Sorry to ask, but is it possible I can get some more help?

You should compile with your warnings turned all the way up. Read your compiler documentation. Here's what I get when I compile your program:

Code:

$ gcc -Wall -g  menu.c   -o menu
menu.c:7: warning: return type defaults to ‘int’
menu.c: In function ‘mostrar_menu’:
menu.c:22: warning: implicit declaration of function ‘ler_ficheiro’
menu.c: In function ‘ler_ficheiro’:
menu.c:51: warning: implicit declaration of function ‘ler_fich_texto’
menu.c: At top level:
menu.c:86: warning: return type defaults to ‘int’
menu.c: In function ‘main’:
menu.c:92: warning: control reaches end of non-void function
menu.c: In function ‘ler_fich_texto’:
menu.c:80: warning: control reaches end of non-void function
menu.c: In function ‘ler_ficheiro’:
menu.c:54: warning: control reaches end of non-void function
menu.c: In function ‘mostrar_menu’:
menu.c:30: warning: control reaches end of non-void function
menu.c: In function ‘ler_fich_texto’:
menu.c:68: warning: ‘stream’ is used uninitialized in this function
/tmp/cc9EfHNG.o: In function `ler_ficheiro':
/home/tyco/sandbox/cprogramming/menu.c:43: warning: the `gets' function is dangerous and should not be used.

For the "implicit declaration" warnings, you need to declare a function before you use it. That means put the whole function above where you call it, or put a prototype at the top of the file.

For the "return type defaults to 'int'" and "control reaches end of non-void function" errors:
In C, if you leave off the return type for a function, it assumes you're going to return an int. If you don't want to return anything from your functions, then make the return type 'void'. main should be declared to explicitly return an int: int mainI(void), and you should put a return 0; as the last line.

Don't use recursion to do your error checking. Use a loop:

Code:

do {
    prompt user
    read input
} while (input is not valid);

You never pass any parameters to your functions or return any useful information from them. Data doesn't magically move between functions, you have to pass it and return it explicitly. If you definitely don't want to pass data, you should make the parameter list void. Start by reading this link: Functions in C - Cprogramming.com, then Google around for some other function tutorials.

As for your seg fault, you use stream uninitialized in ler_fich_texto. It contains garbage data. It's probably not zero, so the if check succeeds, but it also doesn't point to a valid file, so using it in fread is undefined behavior and probably the result of your crash.

You have the function mostrar_menu() calling itself; this is wrong.
Remove it.

Tim S.

on line 45 you're calling ler_fich_texto();
but on line 52 we see it needs a char * argument.