[英]Matlab crash after returning from function that calls MEX
我正在創建一個 MEX 以使用 A* 算法查找兩個節點之間的路徑。 代碼按預期工作,檢索到正確的結果,一切似乎都很好,但是當我從調用 MEX 的方法返回時,Matlab 只是自行關閉。
As I know sometimes Matlab creates a pointer to the same memory address when the user tries to create a copy of a variable (IE A = 3; B = A, then A and B are pointing to the same memory address, even though Matlab shows它們作為 2 個自變量)我使用了一個舊技巧,即直接對變量的副本執行操作,即使它是一個愚蠢的操作,Matlab 會認為這兩個變量不再相同,並將創建它(即 A = 3;B = A;B = B+0,現在 A 和 B 存儲為不同的獨立變量)。
因此,我發現解決此問題的唯一方法是執行 function getWP 中所示的操作:
function testAStarC()
% load the map of the area
load('epsp0_2_nav.mat');
% Set the initial node
initNode = '16x21';
% Set the target node
finalNode = '-15x54';
% Select Heuristic
heuristic = 'Manhattan';
% Create a target location (targetX, targetY, targetAngle)
targetCoords = [-15*110 54*110 0.15];
% Function that hosts the call to the MEX
wp = getWP(map, initNode, finalNode, targetCoords, heuristic);
disp('If you remove the line cellNodes{keyID}.x = cellNodes{keyID}.x; from getWP ...
I wont reach this line');
disp(['Route with ',num2str(length(wp)),' wp found']);
disp('done');
function waypointsList = getWP(map, initNode, finalNode, targetCoords, heuristic)
% HashMap containing the nodes (this is a Java hashmap)
nodesHash = map.navMap.nodes.nodes;
keys = nodesHash.keys();
numNodes = length(keys);
cellNodes = cell(1,numNodes);
% Parse the nodes from the HashMap to Cells as the MEX seems to be
% unable to read directly from the Java HashMap
for keyID=1:numNodes
cellNodes{keyID} = nodesHash(keys{keyID});
%---------------------------------------------------------
% WITHOUTH THIS MATLAB CRASHES WHEN RETURNING FROM GETWP
%---------------------------------------------------------
% We need this to force Matlab to create a new copy of the content,
% otherwise will send a pointer aiming to the HashMap and crash when
% returning from getWP.
cellNodes{keyID}.x = cellNodes{keyID}.x;
end
waypointsList = AStar(cellNodes, initNode, finalNode, targetCoords, heuristic, 1);
disp('I am not crashing here if you remove cellNodes{keyID}.x = cellNodes{keyID}.x');
我的第一個想法是我對 MEX 中的“cellNodes”做錯了,這導致 Matlab 崩潰,但我沒有直接使用輸入參數執行任何操作。 這是節點 class 的構造函數:
節點.cpp
Node::Node(mxArray *cellElement)
{
double *xIn;
double *yIn;
char strIn[15];
double *posXIn;
double *posYIn;
double *weightIn;
double *tempVal;
size_t numCellElms;
mxArray *cellElement2;
numCellElms = mxGetNumberOfFields(cellElement);
size_t size;
for (int cellItem = 0; cellItem < numCellElms; cellItem++)
{
cellElement2 = mxGetCell(cellElement,cellItem);
if (cellItem == 0)
{
xIn = mxGetPr(cellElement2);
memcpy(tempVal,xIn,sizeof(double));
gridX = int(*tempVal);
}
if (cellItem == 1)
{
yIn = mxGetPr(cellElement2);
memcpy(tempVal,yIn,sizeof(double));
gridY = int(*tempVal);
}
if (cellItem >= 2 && cellItem < 10)
{
mwSize buflen = mxGetN(cellElement2)*sizeof(mxChar)+1;
if (buflen <= 1)
{
connections[cellItem-2][0] = '\0';
}
else
{
mxGetString(cellElement2, strIn, buflen);
memcpy(&connections[cellItem-2][0], strIn, buflen);
}
}
if (cellItem == 10)
{
posXIn = mxGetPr(cellElement2);
memcpy(&posX,posXIn,sizeof(double));
}
if (cellItem == 11)
{
posYIn = mxGetPr(cellElement2);
memcpy(&posY,posYIn,sizeof(double));
}
if (cellItem == 12)
{
posXIn = mxGetPr(cellElement2);
memcpy(&wpX,posXIn,sizeof(double));
}
if (cellItem == 13)
{
posYIn = mxGetPr(cellElement2);
memcpy(&wpY,posYIn,sizeof(double));
}
if (cellItem == 14)
{
weightIn = mxGetPr(cellElement2);
memcpy(&weight,weightIn,sizeof(double));
}
}
sprintf(xStr,"%i",gridX);
sprintf(yStr,"%i",gridY);
sprintf(key,"%ix%i",gridX,gridY);
}
這就是我在 AStar.cpp 中初始化節點列表的方式
// Create nodes in the nodes hash
mxArray *cellElement;
std::map<std::string, Node> nodesHash;
for (int nodeID=0; nodeID < numberOfNodes; nodeID++)
{
cellElement = mxGetCell(prhs[0], nodeID);
Node n(cellElement);
nodesHash[n.key] = n;
}
現在表單不再使用 prhs[0],因為沒有改變 prhs[0] 的內容(變量包含指向 Matlab 變量 cellNodes 的指針),這個變量在離開 MEX 后應該完全相同。
從這里我有兩個問題:
謝謝!
*Edit1:在 Windows10 64 位中使用 Matlab 2015b。
1)如果沒有改變第一個參數的內容,為什么從getWP返回時它會崩潰?
[Node.cpp] 'double* tempVal' 未分配,盡管代碼有效,但這可能會破壞 prhs[0] 的完整性,從而導致 Matlab 從調用 MEX 的 function 返回時崩潰。
解決方案是將 tempVal 聲明為“double tempVal[1]”。 之后,testAStarC.m 行 'cellNodes{keyID}.x = cellNodes{keyID}.x;' 可以刪除而不會導致錯誤。
雖然與崩潰無關,但使用 memcpy 獲取標量雙精度已被 mxGetScalar() 取代。
節點構造函數:
Node::Node(mxArray *cellElement)
{
char strIn[15];
double tempVal[1];
size_t numCellElms = mxGetNumberOfFields(cellElement);
mwSize buflen;
for (int cellItem = 0; cellItem < numCellElms; cellItem++)
{
mxArray *cellElement2 = mxGetCell(cellElement,cellItem);
switch (cellItem)
{
case 0:
gridX = (int)mxGetScalar(cellElement2);
break;
case 1:
gridY = (int)mxGetScalar(cellElement2);
break;
case 2:
case 3:
case 4:
case 5:
case 6:
case 7:
case 8:
case 9:
buflen = mxGetN(cellElement2)*sizeof(mxChar)+1;
if (buflen <= 1)
connections[cellItem-2][0] = '\0';
else
{
mxGetString(cellElement2, strIn, buflen);
memcpy(&connections[cellItem-2][0], strIn, buflen);
}
break;
case 10:
posX = mxGetScalar(cellElement2);
break;
case 11:
posY = mxGetScalar(cellElement2);
break;
case 12:
wpX = mxGetScalar(cellElement2);
break;
case 13:
wpY = mxGetScalar(cellElement2);
break;
case 14:
weight = mxGetScalar(cellElement2);
break;
}
}
sprintf(xStr,"%i",gridX);
sprintf(yStr,"%i",gridY);
sprintf(key,"%ix%i",gridX,gridY);
}
測試AStarC.m
function waypointsList = getWP(map, initNode, finalNode, targetCoords, heuristic)
% HashMap containing the nodes (this is a Java hashmap)
nodesHash = map.navMap.nodes.nodes;
keys = nodesHash.keys();
numNodes = length(keys);
cellNodes = cell(1,numNodes);
% Parse the nodes from the HashMap to Cells as the MEX seems to be
% unable to read directly from the Java HashMap
for keyID=1:numNodes
cellNodes{keyID} = nodesHash(keys{keyID});
end
waypointsList = AStar(cellNodes, initNode, finalNode, targetCoords, heuristic, 1);
2) 有沒有更優雅的方式強制 Matlab 創建變量的真實副本? 不,你能做的最好的就是嘗試分配技巧。
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