Realloc 弄乱了我的结构数组

Question

我正在做一个学校项目，我可以在其中管理动物园信息。动物园有区域，它们保存在结构数组中。该区域最多有 3 个相邻区域。当程序初始化时，它必须读取一个已经包含一些区域信息的文件。而且效果很好。我得到了 char areas3[10] so I can save the neighbour areas names, and then search in the array of structures with the Areas and save the neighbour areas in an array of pointers to the struct (Area *adj3) 的结构。在总数达到 6 个区域之前，它工作正常。我找到了问题的根源。 realloc 弄乱了值。但我现在真的不知道为什么以及如何解决它。有人能帮我吗？谢谢

struct.h

typedef struct area Area;
struct area{
    char id[10];
    int peso, nadj;

    char areas[3][10];
    Area *adj[3]; ///ponteiros para areas adjacentes
};

main.c

int menu()
{
    int op;

    printf("\n\n1 - Mostrar Areas");
    printf("\n2 - Nova Area");
    printf("\n3 - Eliminar Area");
    printf("\n4 - Terminar");
    do{
        printf("\nOpcao: ");
        fflush(stdin);
        scanf(" %d", &op);
        putchar('\n');
    }while(op<1 || op>4);
    return op;
}

int main(int argc, char** argv) {

    int i, total;
    FILE *f;    ///FICHEIRO COM ÁREAS
    Area *areas = NULL; ///IMPORTANTE ESTAR A NULL PARA FUNCIONAR

    areas = le_fich("zoo.txt", &total);

    do{
        i = menu();
        switch(i){
            case 1: mostrar_areas(areas, total); break;
            case 2: areas = nova_area(areas, &total); break;
            case 3: printf("Funcao por introduzir."); break;
            case 4: printf("Funcao por introduzir."); break;
        }        
    }while(i != 4);

    free(areas);

    return (EXIT_SUCCESS);
}

funcoes.c

Area *nova_area(Area *p, int *total){
    int i, igual;
    Area *novo;
    char nome_area[TAM], nome_areadj[TAM];


    printf("********BEFORE p[1].adj[0]: %s\n", p[1].adj[0]->id);

    novo = realloc(p, ((*total)+1) * sizeof(Area));
    if(novo == NULL){
        printf("Erro na alocacao de memoria.\n");
        return p;
    }

    printf("******** AFTERp[1].adj[0]: %s\n", p[1].adj[0]->id);

    p = novo;   //CASO p TENHA MUDADO DE SITIO DEVIDO AO REALLOC
    *total = *total +1;

    do{
        printf("ID: ");
        scanf(" %10[^\n]", nome_area);

        igual = procura_area(p, nome_area, *total);
    }while(igual);

    strcpy(p[*total-1].id, nome_area);
    printf("Peso: ");
    scanf(" %d", &(p[*total-1].peso));
    do{
        printf("Nadj: ");
        scanf(" %d", &(p[*total-1].nadj));

        if(p[*total-1].nadj >= 4)
            printf("\tNumero de areas adjacentes excedidas.\n");
    }while(p[*total-1].nadj >= 4);

    for(i = 0; i < p[*total-1].nadj; i++){
        do{
                printf("Nome da area adjacente: ");
                scanf(" %10[^\n]", nome_areadj);
        }while(strcmp(nome_area, nome_areadj) == 0);

        p[*total-1].adj[i] = procura_areaAdj(p, nome_areadj, *total);
        //SE A AREA INSERIDA NAO FOR RECONHECIDA (NULL), O NUMERO DE ADJACENCIAS
        //É DIMINUÍDO
        if(p[*total-1].adj[i] == NULL){
//                p[*total-1].nadj -= p[*total-1].nadj; //AQUIIIIIIIIIIIIIIIIII DA ULTIMA VEZ

            p[*total-1].nadj--;
        }
        else if(p[*total-1].adj[i]->nadj < 3 && p[*total-1].adj[i] != NULL){
            atualiza_areas(p, nome_areadj, *total);
        }
        else{
            p[*total-1].nadj = 0;
            p[*total-1].adj[i] = NULL;
            printf("Numero maximo de areas adjacentes alcancado.\n");
        }
    }
//    printf("********DEPOISp[1].adj[0]: %s\n", p[1].adj[0]->id);
    return p;
}

Answer 1

改变它

Area * nova_area (Area *p, int *total)

至：

Area * nova_area (Area **p, int *total)

你正在通过value.You传递Area，需要传递Area的指针，所以你可以修改和重新分配它。您还需要更改 realloc:

novo = realloc (*p, ((* total) +1) * sizeof (Area));

Answer 2

已经解决了。当我重新分配指向结构数组的指针时，我丢失了其中指针的位置。我的解决方案是：在搜索相邻区域时，我不返回它的指针，而是发送它的索引并轻松管理这些区域。所以现在不会丢失任何指针位置。

struct.h

///STRUCT PARA AS AREAS. INCLUI LISTA LIGADA typedef struct area Area; struct area{
    char id[10];
    int peso, nadj;
    
    char areas[3][10];
    int adj[3]; ///array de indices das areas adjacentes };

funcoes.c

//when searching
int procura_areaAdj(Area *p, char *nome_areadj, int total){
    for(int i = 0; i < total; i++){        
        if(strcmp(nome_areadj, p[i].id) == 0){    //SE ENCONTROU RETORNA O INDICE 
            return i;
        }
    }
    
    return -1;   //SE NÃO ENCONTROU, RETORNA -1. PARA FUTURAS VALIDAÇÕES
}


//UPDATING ARRAY OF STRUCTURES VALUES
void atualiza_areas(Area *p, char *nome_areadj, int total){
    int i, j;

    if(total == 1)  //NAO EXISTEM ATUALIZACOES NA PRIMEIRA AREA INSERIDA
        ;
    else{
        for(i = 0; i < total; i++){        
            if(strcmp(nome_areadj, p[i].id) == 0){
                
                j=0;
                while(j < p[i].nadj)
                    j++;

                p[i].nadj++;
                p[i].adj[j] = total-1; //RETURNS LAST AREA INDEX 
                
            }
        }
    } }

Realloc 弄乱了我的结构数组

Realloc messing with my array of structs

c

struct

pointers

realloc

dynamic-memory-allocation

struct.h

main.c

funcoes.c

struct.h

funcoes.c