Question

我有以下代码：

#include <stdio.h>
#include <stdlib.h>
#include <time.h>

typedef struct persona
{
    char *nombre;
    int edad;
    int sexo;
} Persona;

typedef struct
{
    int size;
    Persona vecPersona[];
} Array;

Array* getArrayInstance()
{
    Array *vec;
    vec = (Array*) malloc (sizeof(Persona));
    vec->size = 0;
    return vec;
}

void push_back(Array ** vec, Persona tipito)
{
    (*vec)->vecPersona[(*vec)->size] = tipito;
    (*vec)->size++;
    printf("%d-", (*vec)->size);
    int newSize = (*vec)->size*2-(*vec)->size+1;
    Array *tmp = realloc((*vec), newSize*sizeof(Persona));
    if(tmp)
        *vec = tmp;
    else
        (*vec)->size--;
}

void mostrarPersonas(Array *vec)
{
    int i;
    printf("\n\n");
    printf("%d", vec->size);
    for(i=0; i<vec->size; i++)
    {
        printf("(%d) Nombre: %s - Edad: %d - Sexo: ", i, vec->vecPersona[i].nombre, vec->vecPersona[i].edad);
        if(vec->vecPersona[i].sexo == 0)
            printf("Masculino");
        else
            printf("Femenino");
        printf("\n");
    }
}

void cargarPersonas(Array **vec)
{
    int i, edad, random;
    int cantPersonas = 3;
    Persona aux;
    char hombres[][20] = {"Ramiro","Pedro","Federico","Jose","Antonio","Pablo","Raul","Gustavo","Gonzalo","Airton"};
    char mujeres[][20] = {"Mariana","Jennifer","Luz","Roxana","Ana","Sol","Micaela","Romina","Melina","Camila"};
    for(i=0; i<cantPersonas; i++)
    {
        edad = rand()%80+1;
        aux.edad = edad;
        if( (random = rand()%10) %2 == 0) 
        {
            aux.nombre = hombres[random];
            aux.sexo = 0;
        }
        else
        {
            aux.nombre = mujeres[random];
            aux.sexo = 1;
        }

        push_back(vec, aux);
    }

}


int main()
{
    srand(time(NULL));
    Array *vecPersonas = getArrayInstance();

    cargarPersonas(&vecPersonas); 
    printf("%d", vecPersonas->size);
    mostrarPersonas(vecPersonas);

    return 0;
}

代码编译没有错误，但是当我执行代码时它会给我带来问题。例如，我在名称字段中得到了奇怪的字符。

示例输出：

<0> Nombre: ?ç!:. - Edad: 25 - Sexo: Maculino

更新

显然问题出在函数 push_back

中

void push_back(Array ** vec, Persona tipito)
{
    (*vec)->vecPersona[(*vec)->size] = tipito;
    (*vec)->size++;

    int newSize =  (*vec)->size + 1;
    Array *tmp = realloc(*vec, (newSize*sizeof(Persona))); // here

    if (!tmp)
    {
        printf("Cannot allocate more memory.\n");
        (*vec)->size--;
    }
    else
        *vec = tmp;
}

Answer 1

第一个错误：

Array* getArrayInstance()
{
    Array *vec;
    vec = (Array*) malloc (sizeof(Persona));
//                               ^^^^^^^^^
//                    should be sizeof(*vec) == sizeof(Array)    
    vec->size = 0;
    return vec;
}

第二个错误：

void push_back(Array ** vec, Persona tipito)
{
    (*vec)->vecPersona[(*vec)->size] = tipito;
//                            ^^^^^^
//                      access out of range
//                      the last object in array is indexed with size-1
//                      if you wanted the first object, which is indexed with 0
//                      then it is still wrong as your vec->size is 0 when there 
//                      is no memory allocated for the array

stdout中的奇怪角色是UB的先知，或者更确切地说是对我们背后留下的维度的投射。

我们程序员应该不惜任何代价避免输出中出现奇怪的字符。每当你看到他们立即采取纠正故障程序的行动时，要注意与访问数组元素相关的代码行，特别是但不限于此。

随机选择姓名时出现奇怪的字符

1 个答案: