The language is portuguese, but I think you get the picture. My main calls only the menu function (the function in comment is the test which works).

In the menu i introduce the option 1 which calls the same function. But there's something wrong.

If i test it solely on the input:

(1/1)x^2 //it reads the polinomyal (2/1) //reads the rational and returns 4

(you can guess what it does, calculates the value of an instace of x over a rational)

My polinomyals are linear linked lists with a coeficient (rational) and a degree (int)

int main ()
{
    menu_interactivo ();
//  instanciacao ();
    return 0;
}

void    menu_interactivo(void)
{
    int i;
    do{
        printf("1. Instanciacao de um polinomio com um escalar\n");
        printf("2. Multiplicacao de um polinomio por um escalar\n");
        printf("3. Soma de dois polinomios\n");
        printf("4. Multiplicacao de dois polinomios\n");
        printf("5. Divisao de dois polinomios\n");
        printf("0. Sair\n");
        scanf ("%d", &i);
        switch  (i)
        {
            case 0: exit(0);
                    break;
            case 1: instanciacao ();
                    break;
            case 2: multiplicacao_esc ();
                    break;
            case 3: somar_pol ();
                    break;
            case 4: multiplicacao_pol ();
                    break;
            case 5: divisao_pol ();
                    break;
            default:printf("O numero introduzido nao e valido!\n");
        }
    }
    while (i != 0);
}

When i call it with the menu, with the same input, it does not stop reading the polinomyal (I know this because it does not ask me for the rational as on the other example)

I've run it with valgrind --track-origins=yes returning the following:

==17482== Memcheck, a memory error detector
==17482== Copyright (C) 2002-2009, and GNU GPL'd, by Julian Seward et al.
==17482== Using Valgrind-3.5.0 and LibVEX; rerun with -h for copyright info
==17482== Command: ./teste
==17482== 
1. Instanciacao de um polinomio com um escalar
2. Multiplicacao de um polinomio por um escalar
3. Soma de dois polinomios
4. Multiplicacao de dois polinomios
5. Divisao de dois polinomios
0. Sair
1
Introduza um polinomio na forma (n0/d0)x^e0 + (n1/d1)x^e1 + ... + (nk/dk)^ek,
com ei > e(i+1):
(1/1)x^2
==17482== Conditional jump or move depends on uninitialised value(s)
==17482==    at 0x401126: simplifica_f (fraccoes.c:53)
==17482==    by 0x4010CB: le_f (fraccoes.c:30)
==17482==    by 0x400CDA: le_pol (polinomios.c:156)
==17482==    by 0x400817: instanciacao (t4.c:14)
==17482==    by 0x40098C: menu_interactivo (t4.c:68)
==17482==    by 0x4009BF: main (t4.c:86)
==17482==  Uninitialised value was created by a stack allocation
==17482==    at 0x401048: le_f (fraccoes.c:19)
==17482== 
==17482== Conditional jump or move depends on uninitialised value(s)
==17482==    at 0x400D03: le_pol (polinomios.c:163)
==17482==    by 0x400817: instanciacao (t4.c:14)
==17482==    by 0x40098C: menu_interactivo (t4.c:68)
==17482==    by 0x4009BF: main (t4.c:86)
==17482==  Uninitialised value was created by a stack allocation
==17482==    at 0x401048: le_f (fraccoes.c:19)
==17482== 

I will now give you the functions which are called

void    le_pol (pol *p)
{
    fraccao f;
    int     e;
    char    c;

    printf ("Introduza um polinomio na forma (n0/d0)x^e0 + (n1/d1)x^e1 + ... + (nk/dk)^ek,\n");
    printf("com ei > e(i+1):\n");

    *p = NULL;

    do
    {
        le_f (&f);

        getchar();
        getchar();

        scanf ("%d", &e);

        if (f.n != 0)
            *p = add (*p, f, e);

        c = getchar ();

        if (c != '\n')
        {
                getchar();
                getchar();
        }
    }
    while (c != '\n');
}


void    instanciacao (void)
{
    pol     p1;
    fraccao f;

    le_pol (&p1);
    printf ("Insira uma fraccao na forma (n/d):\n");
    le_f (&f);
    escreve_f(inst_esc_pol(p1, f));
}


void    le_f (fraccao *f)
{
    int n, d;

    getchar ();
    scanf ("%d", &n);
    getchar ();
    scanf ("%d", &d);
    getchar ();

    assert (d != 0);

    *f = simplifica_f(cria_f(n, d));
}

simplifica_f simplifies a rational and cria_f creates a rationa given the numerator and the denominator

Can someone help me please? Thanks in advance.

If you want me to provide some tests, just post it.

See ya.