C language - Why my char vector is getting NULL in the first position after a scanf of another variable

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When executing the code below, choosing the option 2 the name is entered "Teste Nome", the struct pessoas[i].nome gets the value Teste Nome\n\000 shortly after the fgets(). However, after the scanf() (which is used to punctuate the struct pessoas[i].idade), the struct pessoas[i].nome gets the value \000\000\000te Nome\n\000

Please, can anyone tell me where I went wrong? I can’t find the bug at all.

#include<stdio.h>
#include <conio.h> // para leitura do nome
#define MAX 1
#define MAX_NOME 50

struct pessoa{
    char idade;
    char nome[MAX_NOME];
};

void main(){
    
    short opcao;
    struct pessoa pessoas[MAX];
    int i;
    
    do {
        printf("\n2 - Carregar os dados manualmente\n");
        printf("6 - Exibir todas as pessoas\n");
        printf("0 - S A I R\nOpcao: ");
        fflush(stdin);
        scanf("%d", &opcao);
        
        switch(opcao) {
            case 2: // Carregar os dados manualmente
                for (i = 0; i < MAX; i++) {
                    printf("Nome: ");
                    fflush(stdin);
                    fgets(pessoas[i].nome, MAX_NOME, stdin);
                    printf("Idade: ");
                    scanf("%d", &pessoas[i].idade);
                    
                }
                
                break;
            case 6: //Exibir todas as pessoas
                for (i = 0; i < MAX; i++) {
                    printf("Idade: %2d - Nome: %s\n", pessoas[i].idade, pessoas[i].nome);
                }
                
                break;
            case 0: //S A I R
                // Nao faz nada
                
                break;
            default:
                printf("\nOpcao invalida\n");
                
                break;
        }
        
    } while(opcao != 0);
    
}
c

  • fflush(stdin) generates undefined behavior, then it is not recommended to use (and even if it did, it should be called after the scanf, not before). Anyway, the problem is mixing scanf and fgets, take a look here and here. And why age is one char and not a int?

  • @hkotsubo thanks for the guidelines. I read all the shared links. In fact, the age variable was with the wrong type. I switched to short. However, even with all this the system did not work. Although my question won one (-2), I asked many questions before coming here. What solved the bug itself was the scanf() that was being used erroneously. I’ll answer my own question so other people can see someday.

1 answer

1

As already pointed out by @hkotsubo, it was necessary to change the char idade for short idade. In addition, the scanf() was also wrong: . When reading a type variable short, we should use the parameter "%hd" and not the "%d" (facing int).

  • I don’t see much point in using short, even more in a small program like this. Use int even: https://stackoverflow.com/a/24371078

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