我有结构,我为它分配内存:
TRANSITION *transitions = malloc(sizeof(TRANSITION *));
我在程序的另一部分添加了转换,所以我重新分配了内存:
TRANSITION *transitions = source->transitions;
transitions = realloc(transitions, (numberTransitions + 1) * sizeof(TRANSITION *));
我有一种想释放记忆的方法:
free(transitions);
当我调用免费方法时,我得到:
"Aborted (core dumped)"
有什么问题?
整个代码:
#include <stdio.h>
#include <stdbool.h>
#include <stdlib.h>
#include <string.h>
typedef struct STATE STATE;
typedef struct TRANSITION TRANSITION;
struct STATE
{
char name[4];
bool initial_state;
bool final_state;
TRANSITION *transitions;
int numberTransitions;
};
struct TRANSITION
{
char c;
STATE *destination;
};
STATE *create_state(char *name, bool is_initial, bool is_final);
void add_transition(STATE *source, char sign, STATE *dest);
void destroy_state(STATE **pp_state);
int main(void)
{
STATE *state0 = create_state("S'0", true, false);
STATE *state1 = create_state("S'1", false, false);
STATE *state2 = create_state("S'2", false, true);
STATE *zero_state = create_state("0", false, false);
add_transition(state0, 'a', state1);
add_transition(state0, 'b', zero_state);
add_transition(zero_state, 'a', zero_state);
add_transition(zero_state, 'b', zero_state);
add_transition(state1, 'a', state1);
add_transition(state1, 'b', state2);
add_transition(state2, 'a', state1);
add_transition(state2, 'b', state2);
destroy_state(&state0);
}
STATE *create_state(char *name, bool is_initial, bool is_final)
{
STATE *state = malloc(sizeof(STATE *));
strcpy(state->name, name);
state->initial_state = is_initial;
state->final_state = is_final;
state->transitions = NULL;
state->numberTransitions = 0;
return state;
}
void add_transition(STATE *source, char sign, STATE *dest)
{
if (source->transitions == NULL)
{
TRANSITION *transitions = malloc(sizeof(TRANSITION *));
transitions->c = sign;
transitions->destination = malloc(sizeof(STATE *));
transitions->destination = dest;
source->transitions = transitions;
source->numberTransitions = 1;
}
else
{
TRANSITION *transitions = source->transitions;
int numberTransitions = source->numberTransitions;
transitions = realloc(transitions, (numberTransitions + 1) * sizeof(TRANSITION *));
transitions[numberTransitions].c = sign;
transitions[numberTransitions].destination = dest;
(source->numberTransitions)++;
}
}
void destroy_state(STATE **pp_state)
{
TRANSITION *transitions = (*pp_state)->transitions;
// free(transitions->destination);
// transitions->destination = NULL;
free(transitions);
// transitions = NULL;
// free(pp_state);
// pp_state = NULL;
}
答案 0 :(得分:3)
我认为你想要malloc sizeof(TRANSITION)而不是sizeof(TRANSITION *)。首先是分配TRANSITION结构的大小,第二个只是mallocs指针的大小,可能小于结构大小。
答案 1 :(得分:2)
我更喜欢像这样调用malloc
:
T *t = malloc(sizeof(*t));
这样你的分配总是指针所指向的对象的大小。
这当然等同于:
T *t = malloc(sizeof(T));
但避免在t
类型发生变化时出错。
答案 2 :(得分:1)
修复分配后,您需要将realloc
的返回值存储在source
中。您还需要检查分配是否成功。
目前您将旧指针保留在source
中,因此当您尝试释放内存时,该块已被释放,并且实际分配的内存已泄漏,因为它未存储在任何位置。