通常、関数にパラメーターとして渡される構造データにアクセスしようとすると、いくつかの関数で実行時エラーが発生します。
問題の最初の例は次のとおりです。
signed portBASE_TYPE xQueueGenericReceive( xQueueHandle pxQueue, void * const p\
vBuffer, portTickType xTicksToWait, portBASE_TYPE xJustPeeking )
{
..............
if( pxQueue->uxMessagesWaiting > ( unsigned portBASE_TY\
PE ) 0 )
.......................
}
ここで、pxQueue は構造体です。
typedef xQUEUE * xQueueHandle;
と：
typedef struct QueueDefinition
{
signed char *pcHead; /*< Points to the begin\
ning of the queue storage area. */
signed char *pcTail; /*< Points to the byte \
at the end of the queue storage area. Once more byte is allocated than necessa\
ry to store the queue items, this is used as a marker. */
signed char *pcWriteTo; /*< Points to the free \
next place in the storage area. */
signed char *pcReadFrom;
/*< Points to the last \
place that a queued item was read from. */
xList xTasksWaitingToSend; /*< List of tas\
ks that are blocked waiting to post onto this queue. Stored in priority order.\
*/
xList xTasksWaitingToReceive; /*< List of tasks that \
are blocked waiting to read from this queue. Stored in priority order. */
volatile unsigned portBASE_TYPE uxMessagesWaiting;/*< The number of ite\
ms currently in the queue. */
unsigned portBASE_TYPE uxLength; /*< The length of the q\
ueue defined as the number of items it will hold, not the number of bytes. */
unsigned portBASE_TYPE uxItemSize; /*< The size of each it\
ems that the queue will hold. */
signed portBASE_TYPE xRxLock; /*< Stores the number o\
f items received from the queue (removed from the queue) while the queue was lo\
cked. Set to queueUNLOCKED when the queue is not locked. */
signed portBASE_TYPE xTxLock; /*< Stores the number o\
f items transmitted to the queue (added to the queue)
while the queue was locke\
d. Set to qu.......................
}
ここで、pxQueue は構造体です。
typedef xQUEUE * xQueueHandle;
と：
typedef struct QueueDefinition
{
signed char *pcHead; /*< Points to the begin\
ning of the queue storage area. */
signed char *pcTail; /*< Points to the byte \
at the end of the queue storage area. Once more byte is allocated than necessa\
ry to store the queue items, this is used as a marker. */
signed char *pcWriteTo; /*< Points to the free \
next place in the storage area. */
signed char *pcReadFrom;
/*< Points to the last \
place that a queued item was read from. */
xList xTasksWaitingToSend; /*< List of tas\
ks that are blocked waiting to post onto this queue. Stored in priority order.\
*/
xList xTasksWaitingToReceive; /*< List of tasks that \
are blocked waiting to read from this queue. Stored in priority order. */
volatile unsigned portBASE_TYPE uxMessagesWaiting;/*< The number of ite\
ms currently in the queue. */
unsigned portBASE_TYPE uxLength; /*< The length of the q\
ueue defined as the number of items it will hold, not the number of bytes. */
unsigned portBASE_TYPE uxItemSize; /*< The size of each it\
ems that the queue will hold. */
signed portBASE_TYPE xRxLock; /*< Stores the number o\
f items received from the queue (removed from the queue) while the queue was lo\
cked. Set to queueUNLOCKED when the queue is not locked. */
signed portBASE_TYPE xTxLock; /*< Stores the number o\
f items transmitted to the queue (added to the queue)
while the queue was locke\
d. Set to queueUNLOCKED when the queue is not locked. */
} xQUEUE;
eueUNLOCKED when the queue is not locked. */
} xQUEUE;
実行時エラーは次のとおりです。
.....
COREB: start xQueueGenericReceive
COREB: execption 24 addr 3c00384
COREB: coreb dump stack
COREB: found fp: ff700900
COREB: call frame 0 -12 feb055e2
COREB: call frame 0 -11 00000000
COREB: call frame 0 -9 00000000
COREB: call frame 0 -8 ff7008d0
......
同様に、次の関数にも同じ問題があります。
void vListRemove( xListItem *pxItemToRemove )
{
xList * pxList;
pxItemToRemove->pxNext->pxPrevious = pxItemToRemove->pxPrevious;
pxItemToRemove->pxPrevious->pxNext = pxItemToRemove->pxNext;
}
pxItemToRemove->pxPrevious は読み取れますが、pxItemToRemove->pxNext->pxPrevious は読み取れません
その構造は次のとおりです。
struct xLIST_ITEM
{
portTickType xItemValue; /*< The value b\
eing listed. In most cases this is used to sort the list in descending order. \
*/
volatile struct xLIST_ITEM * pxNext; /*< Pointer to the next xListIt\
em in the list. */
volatile struct xLIST_ITEM * pxPrevious;/*< Pointer to the previous xLi\
stItem in the list. */
void * pvOwner; /*< Poi\
nter to the object (normally a TCB) that contains the list item. There is ther\
efore a two way link between the object containing the list item and the list i\
tem itself. */
void * pvContainer; /*< Poi\
nter to the list in which this list item is placed (if any). */
};
typedef struct xLIST_ITEM xListItem; /* For some reason lint wants t\
his as two separate definitions. */
実行時エラーは次のとおりです。
COREB: got to vTaskDelete
COREB: pxTCB GLI prev: a5a5a5a5
COREB: sent to list: 3d02004
COREB: list_rem px prev: a5a5a5a5
COREB: execption 24 addr 3c05444
COREB: coreb dump stack
COREB: found fp: ff7008fc
COREB: call frame 0 -12 feb055e2
COREB: call frame 0 -11 00000000
COREB: call frame 0 -9 00000000
COREB: call frame 0 -8 ff7008cc
COREB: call frame 0 -7 ff700ff4
前もって感謝します。
ウィリアム
gdb を使用してさらにデバッグすると、pxQueue があります。
p/x *pxQueue
$9 = {pcHead = 0xadadadad, pcTail = 0xadadadad, pcWriteTo = 0xadadadad,
pcReadFrom = 0xadadadad, xTasksWaitingToSend = {
uxNumberOfItems = 0xadadadad, pxIndex = 0xadadadad, xListEnd = {
xItemValue = 0xadad, pxNext = 0xadadadad, pxPrevious = 0xadadadad}},
xTasksWaitingToReceive = {uxNumberOfItems = 0xadadadad,
pxIndex = 0xadadadad, xListEnd = {xItemValue = 0xadad,
pxNext = 0xadadadad, pxPrevious = 0xadadadad}},
uxMessagesWaiting = 0xadadadad, uxLength = 0xadadadad,
uxItemSize = 0xadadadad, xRxLock = 0xadadadad, xTxLock = 0xadadadad}
本当に奇妙です。構造体のすべてのパラメーターが同じ値を持っています: 0xadadadad
さらにデバッグして、セマフォの作成をキュー作成関数のキュー オブジェクトとして見ると、通常の値が得られます。
p *pxNewQueue
$7 = {pcHead = 0x3d17000 "", pcTail = 0x3d17000 "", pcWriteTo = 0x3d17000 "",
pcReadFrom = 0x3d17000 "", xTasksWaitingToSend = {uxNumberOfItems = 0,
pxIndex = 0x3d16018, xListEnd = {xItemValue = 65535, pxNext = 0x3d16018,
pxPrevious = 0x3d16018}}, xTasksWaitingToReceive = {uxNumberOfItems = 0,
pxIndex = 0x3d1602c, xListEnd = {xItemValue = 65535, pxNext = 0x3d1602c,
pxPrevious = 0x3d1602c}}, uxMessagesWaiting = 0, uxLength = 1,
uxItemSize = 0, xRxLock = -1, xTxLock = -1}
ありがとう、
ウィリアム