opencv Mat deallocation memory corruption

Question

I am struggling with release version of my opencv wrapper function. The function code runs fine, but upon function block completition, memory access violation happens. This problem does not appear in debug mode. The segfault happens upon freeing the heap.

int Myfunc(Arr1D_floatHdl FeatArrHdl, IMAQ_Image *img, someparams 
*Params)
{
ImageInfo *Info = NULL;
//IplImage *CVImage = NULL;
Info = (ImageInfo*)img->address;
CheckImage(Info, Info);
//CVImage = cvCreateImageHeader( cvSize(Info->xRes, Info->yRes), IPL_DEPTH_8U, 4);
//CVImage->imageData = (char*)Info->imageStart;
//CVImage->widthStep = Info->xRes*sizeof(IPL_DEPTH_8U);
cv::Mat BGRAimg = cv::Mat(Info->yRes, Info->xRes, CV_8UC4, (char*)Info->imageStart, sizeof(CV_8UC4)*Info->xRes);
//cv::Mat BGRAimg(CVImage);
//cv::Mat BGRAimg = imread( "MyImg.png", cv::IMREAD_COLOR );
cv::Mat GREYimg;
cv::cvtColor(BGRAimg, GREYimg, CV_BGR2GRAY);

Here is the code where I create Mat object from user supplied data. I tried to create IplImage first (commented version in code) and use Mat constructor with IplImage argument, but eneded up with the same problem. I know I am doing something very wrong during the Mat construction, since manualy loading the image from disk does not cause the issue.

After creating the Mat object, all its parameters are correct and the image is fine. When comparing with the grey matrix created of it, it has refcount NULL, which I have read is perfectly fine since it is supposed to keep user data intact.

Please help.

UPDATE to give more information

Thank you for suggestions. I am obviously prone to create such errors, I am new to C/C++. Unfortunately, the access violation still persists.

Here is the complete wrapper function as it is. I tried to narrow down the problem, and skipping the HOG.compute function I do no longer get memory corruption. Skipping the memcpy acrobatics in the end, I still get the memory corrupted.

int GetHOGFeatures(Arr1D_floatHdl FeatArrHdl, IMAQ_Image *img, HogParams *Params) //returns -1 on HOG window parameters missmatch
{
ImageInfo *Info = NULL;
Info = (ImageInfo*)img->address;
CheckImage(Info, Info);

cv::Mat BGRAimg = cv::Mat(Info->yRes, Info->xRes, CV_8UC4, (char*)Info->imageStart, sizeof(cv::Vec4b)*Info->xRes);
cv::Mat GREYimg;
cv::cvtColor(BGRAimg, GREYimg, CV_BGRA2GRAY);

//set params into hog object
cv::HOGDescriptor hog;
hog.winSize = cv::Size(Params->winsize_width, Params->winsize_height);
hog.blockSize = cv::Size(Params->blocksize_width, Params->blocksize_height);
hog.blockStride = cv::Size(Params->blockstride_x, Params->blockstride_y);
hog.cellSize = cv::Size(Params->cellsize_width, Params->cellsize_height);
hog.nbins = Params->nBins;
hog.derivAperture = Params->derivAperture;
hog.winSigma = Params->win_sigma;
hog.L2HysThreshold = Params->threshold_L2hys;
hog.gammaCorrection = (Params->gammaCorrection != 0);

MgErr error = mgNoErr;

cv::vector ders;
cv::vector locations;

try
{
    //winstride - step of window
    //padding - borderpadding
    //raises exception with incorrect params ... todo replace trycatch with paramchecking
    hog.compute(GREYimg, ders, cv::Size(Params->winstride_x, Params->winstride_y), cv::Size(0,0), locations);
}
catch(...)
{
    return -1;
}
//copy out the data into LabView
error = DSSetHandleSize(FeatArrHdl, sizeof(int32_t) + ders.size()*sizeof(float));
memcpy((*FeatArrHdl)->Arr, ders.data(), sizeof(float)*ders.size());
(*FeatArrHdl)->dimSize = ders.size();

return error;

}

I am running this function with following parameters:

Window size 32 Block size 16 Cell size 8 Block stride 8

Window stride 32

the rest of parameters is default.

I decided to include the look of the Mat object once constructed, I hope it can help.

This is the BGRA constructed from user data. It is supposed to be 640*640 BGRA

BGRAimg {flags=1124024344 dims=2 rows=640 ...} cv::Mat flags 1124024344 int dims 2 int rows 640 int cols 640 int
data 0x12250040 "e9%" unsigned char * 101 'e' unsigned char
refcount 0x00000000 int * CXX0030: Error: expression cannot be evaluated
datastart 0x12250040 "e9%" unsigned char * 101 'e' unsigned char
dataend 0x123e0040 "" unsigned char * 0 unsigned char
datalimit 0x123e0040 "" unsigned char * 0 unsigned char
allocator 0x00000000 cv::MatAllocator * __vfptr CXX0030: Error: expression cannot be evaluated
size {p=0x0012f44c } cv::Mat::MSize
p 0x0012f44c int * 640 int
step {p=0x0012f474 buf=0x0012f474 } cv::Mat::MStep
p 0x0012f474 unsigned int * 2560 unsigned int
buf 0x0012f474 unsigned int [2] [0] 2560 unsigned int [1] 4 unsigned int

And the Grey image that enters the HOG descriptors calculator

GREYimg {flags=1124024320 dims=2 rows=640 ...} cv::Mat flags 1124024320 int dims 2 int rows 640 int cols 640 int
refcount 0x0c867ff0 int * 1 int
dataend 0x0c867ff0 "" unsigned char * 1 '' unsigned char
datalimit 0x0c867ff0 "" unsigned char * 1 '' unsigned char
allocator 0x00000000 cv::MatAllocator * __vfptr CXX0030: Error: expression cannot be evaluated
size {p=0x0012f40c } cv::Mat::MSize
p 0x0012f40c int * 640 int
step {p=0x0012f434 buf=0x0012f434 } cv::Mat::MStep
p 0x0012f434 unsigned int * 640 unsigned int
buf 0x0012f434 unsigned int [2] [0] 640 unsigned int [1] 1 unsigned int

I had to ommit the data and datastart fields, because unlike for the BGRA image MSVS actually shows some data in it.

UPDATE2

changed multi-threaded for multi-threaded DLL in project properities, and the issue is gone.

The problem persisted even if I was using code like this :

int dim = 32;
BYTE *mydata = NULL;
mydata = (BYTE*)malloc(sizeof(BYTE)*dim*dim);
Mat img;
img = Mat(Size(dim,dim), CV_8U, mydata, dim*sizeof(BYTE));

Might this indicate my code was not the cause, and this is somewhat opencv x windows runtime issue, or did I just hide the problem ?

UPDATE3

After reading something about microsoft runtime, I decided to check how was my opencv built, and it is using /MD, and I was building with /MT. I hope this was the cause.

opencv Mat deallocation memory corruption

Answers (1)

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