[英]Invalid memory read - Valgrind
目前,我正在創建2D游戲,但是為了避免所有圖形和聲音開銷(如果有幫助,我打算使用allegro進行處理),因此將其作為命令行游戲進行原型制作。
該代碼按預期工作,到目前為止沒有問題。 即使當我使用valgrind檢查是否未檢測到內存泄漏時,我也看到沒有泄漏可能作為valgrind狀態出現。
但是,我看到一些行指出valgrind檢測到大小為8 .. 的無效讀取,這是我之前從未遇到過的問題,最終也沒有解決方法的線索。
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#define MAX_X_GRID (3)
#define MAX_Y_GRID (3)
#define MAX_NUM ((int)(MAX_X_GRID * MAX_Y_GRID))
typedef struct
{
int x;
int y;
} Location;
typedef struct
{
char * description;
char * name;
Location * location;
} Room;
Room *allrooms[MAX_NUM];
int num;
Room *Room_get_at_location(Location locs)
{ /* Get the room at location locs */
Room *r = NULL;
for ( int i = 0; i < MAX_NUM; ++i ) {
r = allrooms[i];
if ((r->location->x == locs.x) && (r->location->y == locs.y))
return r;
}
return NULL;
}
void Room_destroy(Room *room)
{ /* Free Room memory */
free(room->description);
free(room->name);
free(room->location);
free(room);
}
void free_allrooms()
{ /* Destroy all rooms */
Room *r;
for(int x = 1; x <= MAX_X_GRID; ++x)
for(int y = 1; y <= MAX_Y_GRID; ++y)
if ((r = Room_get_at_location((Location){x, y})) != NULL)
Room_destroy(r);
num = 0;
}
Room *Room_create(char *name, char *desc, Location locs)
{ /* Creates a new room */
if (num == MAX_NUM)
return NULL;
Room *r = malloc(sizeof(Room));
r->description = strdup(desc);
r->name = strdup(name);
r->location = malloc(sizeof(Location));
r->location->x = locs.x;
r->location->y = locs.y;
allrooms[num++] = r;
return r;
}
int main(int argc, char const *argv[])
{
num = 0;
Room *r;
for(int x = 1; x <= MAX_X_GRID; ++x) {
for (int y = 1; y <= MAX_Y_GRID; ++y) {
r = Room_create("Main Hall", "Gee, that's the Main Hall .. !", (Location){x, y});
printf("==========\t%s\t[%d, %d]\t==========\n %s\n", r->name, r->location->x, r->location->y, r->description);
}
}
free_allrooms();
return 0;
}
==6137== Memcheck, a memory error detector
==6137== Copyright (C) 2002-2013, and GNU GPL'd, by Julian Seward et al.
==6137== Using Valgrind-3.10.0 and LibVEX; rerun with -h for copyright info
==6137== Command: ./Main
==6137==
==6137== Invalid read of size 8
==6137== at 0x400604: Room_get_at_location (Main.c:30)
==6137== by 0x4006B4: free_allrooms (Main.c:49)
==6137== by 0x40084A: main (Main.c:79)
==6137== Address 0x51d9050 is 16 bytes inside a block of size 24 free'd
==6137== at 0x4C2B200: free (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==6137== by 0x400680: Room_destroy (Main.c:41)
==6137== by 0x4006CB: free_allrooms (Main.c:50)
==6137== by 0x40084A: main (Main.c:79)
==6137==
==6137== Invalid read of size 4
==6137== at 0x400608: Room_get_at_location (Main.c:30)
==6137== by 0x4006B4: free_allrooms (Main.c:49)
==6137== by 0x40084A: main (Main.c:79)
==6137== Address 0x51d9150 is 0 bytes inside a block of size 8 free'd
==6137== at 0x4C2B200: free (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==6137== by 0x400674: Room_destroy (Main.c:40)
==6137== by 0x4006CB: free_allrooms (Main.c:50)
==6137== by 0x40084A: main (Main.c:79)
==6137==
==6137== Invalid read of size 8
==6137== at 0x400615: Room_get_at_location (Main.c:30)
==6137== by 0x4006B4: free_allrooms (Main.c:49)
==6137== by 0x40084A: main (Main.c:79)
==6137== Address 0x51d9050 is 16 bytes inside a block of size 24 free'd
==6137== at 0x4C2B200: free (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==6137== by 0x400680: Room_destroy (Main.c:41)
==6137== by 0x4006CB: free_allrooms (Main.c:50)
==6137== by 0x40084A: main (Main.c:79)
==6137==
==6137== Invalid read of size 4
==6137== at 0x400619: Room_get_at_location (Main.c:30)
==6137== by 0x4006B4: free_allrooms (Main.c:49)
==6137== by 0x40084A: main (Main.c:79)
==6137== Address 0x51d9154 is 4 bytes inside a block of size 8 free'd
==6137== at 0x4C2B200: free (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==6137== by 0x400674: Room_destroy (Main.c:40)
==6137== by 0x4006CB: free_allrooms (Main.c:50)
==6137== by 0x40084A: main (Main.c:79)
==6137==
========== Main Hall [1, 1] ==========
Gee, that's the Main Hall .. !
========== Main Hall [1, 2] ==========
Gee, that's the Main Hall .. !
========== Main Hall [1, 3] ==========
Gee, that's the Main Hall .. !
========== Main Hall [2, 1] ==========
Gee, that's the Main Hall .. !
========== Main Hall [2, 2] ==========
Gee, that's the Main Hall .. !
========== Main Hall [2, 3] ==========
Gee, that's the Main Hall .. !
========== Main Hall [3, 1] ==========
Gee, that's the Main Hall .. !
========== Main Hall [3, 2] ==========
Gee, that's the Main Hall .. !
========== Main Hall [3, 3] ==========
Gee, that's the Main Hall .. !
==6137==
==6137== HEAP SUMMARY:
==6137== in use at exit: 0 bytes in 0 blocks
==6137== total heap usage: 36 allocs, 36 frees, 657 bytes allocated
==6137==
==6137== All heap blocks were freed -- no leaks are possible
==6137==
==6137== For counts of detected and suppressed errors, rerun with: -v
==6137== ERROR SUMMARY: 90 errors from 4 contexts (suppressed: 0 from 0)
我做錯了什么?
函數Room_get_at_location
存在問題。 在您一一釋放房間時,在某些情況下,調用Room_get_at_location
時可能已經釋放了一些房間。 在釋放的條目上保留r = allrooms[i]
測試字段會生成未定義的行為。
將其釋放后,將NULL
分配給數組allrooms
的條目(更改指針的Room_get_at_location
的返回值Room_get_at_location
),然后在Room_get_at_location
跳過它們:
Room *Room_get_at_location(Location locs)
{ /* Get the room at location locs */
Room *r = NULL;
for ( int i = 0; i < MAX_NUM; ++i ) {
r = allrooms[i];
if (!r)
continue;
if ((r->location->x == locs.x) && (r->location->y == locs.y))
return r;
}
return NULL;
}
我已經根據上面的解決方案編輯了代碼,這次valgrind
沒有提出任何抱怨。
編輯后的代碼如下。 請注意,這僅用於測試,我確實認為此修復程序很難看。 您絕對可以重新設計它。
#define _POSIX_C_SOURCE 201401L
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#define MAX_X_GRID (3)
#define MAX_Y_GRID (3)
#define MAX_NUM ((int)(MAX_X_GRID * MAX_Y_GRID))
typedef struct
{
int x;
int y;
} Location;
typedef struct
{
char * description;
char * name;
Location * location;
} Room;
Room *allrooms[MAX_NUM];
int num;
Room **Room_get_at_location(Location locs)
{ /* Get the room at location locs */
Room **r = NULL;
for ( int i = 0; i < MAX_NUM; ++i ) {
r = &allrooms[i];
if (!*r)
continue;
if (((*r)->location->x == locs.x) && ((*r)->location->y == locs.y))
return r;
}
return NULL;
}
void Room_destroy(Room *room)
{ /* Free Room memory */
free(room->description);
free(room->name);
free(room->location);
free(room);
}
void free_allrooms()
{ /* Destroy all rooms */
Room **r;
for(int x = 1; x <= MAX_X_GRID; ++x)
for(int y = 1; y <= MAX_Y_GRID; ++y)
{
r = Room_get_at_location((Location){x, y});
if (*r)
{
Room_destroy(*r);
*r = NULL;
}
}
num = 0;
}
Room *Room_create(char *name, char *desc, Location locs)
{ /* Creates a new room */
if (num == MAX_NUM)
return NULL;
Room *r = malloc(sizeof(Room));
r->description = strdup(desc);
r->name = strdup(name);
r->location = malloc(sizeof(Location));
r->location->x = locs.x;
r->location->y = locs.y;
allrooms[num++] = r;
return r;
}
int main(int argc, char const *argv[])
{
num = 0;
Room *r;
for(int x = 1; x <= MAX_X_GRID; ++x) {
for (int y = 1; y <= MAX_Y_GRID; ++y) {
r = Room_create("Main Hall", "Gee, that's the Main Hall .. !", (Location){x, y});
printf("==========\t%s\t[%d, %d]\t==========\n %s\n", r->name, r->location->x, r->location->y, r->description);
}
}
free_allrooms();
return 0;
}
結果:
[pengyu@GLaDOS tmp]$ gcc a.c -std=c11 -Wall -ggdb
[pengyu@GLaDOS tmp]$ valgrind ./a.out
==20749== Memcheck, a memory error detector
==20749== Copyright (C) 2002-2013, and GNU GPL'd, by Julian Seward et al.
==20749== Using Valgrind-3.10.0 and LibVEX; rerun with -h for copyright info
==20749== Command: ./a.out
==20749==
========== Main Hall [1, 1] ==========
Gee, that's the Main Hall .. !
========== Main Hall [1, 2] ==========
Gee, that's the Main Hall .. !
========== Main Hall [1, 3] ==========
Gee, that's the Main Hall .. !
========== Main Hall [2, 1] ==========
Gee, that's the Main Hall .. !
========== Main Hall [2, 2] ==========
Gee, that's the Main Hall .. !
========== Main Hall [2, 3] ==========
Gee, that's the Main Hall .. !
========== Main Hall [3, 1] ==========
Gee, that's the Main Hall .. !
========== Main Hall [3, 2] ==========
Gee, that's the Main Hall .. !
========== Main Hall [3, 3] ==========
Gee, that's the Main Hall .. !
==20749==
==20749== HEAP SUMMARY:
==20749== in use at exit: 0 bytes in 0 blocks
==20749== total heap usage: 36 allocs, 36 frees, 657 bytes allocated
==20749==
==20749== All heap blocks were freed -- no leaks are possible
==20749==
==20749== For counts of detected and suppressed errors, rerun with: -v
==20749== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)
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