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chamerMatching malloc error

asked 2014-02-13 16:21:37 -0500

bluestreak209 gravatar image

updated 2018-10-04 23:47:36 -0500

I am having an error trying to do chamfer matching. Somewhere within the call to chamerMatching, I get the error:

malloc: * error for object 0x104044000: pointer being freed was not allocated * set a breakpoint in malloc_error_break to debug

Here is the code:

Mat img = imread(argc == 3 ? argv[1] : "X077_03.jpg", CV_LOAD_IMAGE_GRAYSCALE); 
Mat tpl = imread(argc == 3 ? argv[2] : "X077_03.jpg", CV_LOAD_IMAGE_GRAYSCALE);
Canny(img, img, 5, 50, 3);
Canny(tpl, tpl, 5, 50, 3);
vector<vector<Point> > results;
vector<float> costs;
int best = chamerMatching( img, tpl, results, costs );

Does anyone have a guess as to what could be going on?

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2 answers

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answered 2014-03-11 11:13:05 -0500

aecins gravatar image

I have had a similar issue that might be related to yours. I was trying to run the sample Chmafer matching code from OpenCV (/trunk/opencv/samples/cpp/chamfer.cpp) and I would get the following error:

* glibc detected :double free or corruption (!prev): 0x0000000000745bb0 **

The reason is that in function chamerMatching(img, tpl, results, costs) a template is created and then a reference to it is added inside matcher_ object:

ChamferMatcher::Template template_(templ, (float)templScale);
ChamferMatcher::Matches match_instances = matcher_.matching(template_, img);

As a result when the function returns template_ is destroyed first and then when matcher_ is destroyed it tries to destroy the same template again hence you gen an error.

A quick fix to it is to modify the destructor of Matching() and to comment out the line that deletes templates.

    ~Matching()
    {
        for (size_t i = 0; i<templates.size(); i++) {
            //delete templates[i];
        }
    }

Note, however, that this solution is just a hack that I used to get the demo working. There might be other ways templates can be added to Matching object and those need to be deleted otherwise you will get memory leak.

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Comments

would you be so nice to make an issue here , so someone can have a go at fixing it ?

berak gravatar imageberak ( 2014-03-11 11:30:41 -0500 )edit
aecins gravatar imageaecins ( 2014-03-11 12:04:45 -0500 )edit

well done, thanks a lot.

berak gravatar imageberak ( 2014-03-11 12:09:07 -0500 )edit

Have you found another better solution? I don't understand very well yours. Why don't run the sample? I have the same error than you

fortes_23 gravatar imagefortes_23 ( 2015-01-06 14:00:45 -0500 )edit
0

answered 2016-08-29 14:27:04 -0500

Charles Tallman gravatar image

updated 2016-08-29 14:57:33 -0500

I found that the Template ownership and lifetime issues get quite complicated. At the heart of the problem is the ChamferMatcher::Template::rescale function, which can either return "this" or a new-allocated Template object. A template can also hold scaled templates in an internal vector. Template pointers can also be copied to Matching, etc.

If one is willing to use the modern C++11 standard library, the problems can be resolved with std::shared_ptr, which does reference counting and only destroys an object when the last pointer to it is destroyed.

std::shared_ptr<ChamferMatcher::Template> ChamferMatcher::Template::rescale(float new_scale)
{

if (fabs(scale - new_scale) < 1e-6) return shared_from_this();

for (size_t i=0;i<scaled_templates.size();++i) {
    if (fabs(scaled_templates[i]->scale-new_scale)<1e-6) {
        return scaled_templates[i];
    }
}

float scale_factor = new_scale/scale;

auto tpl = std::make_shared<Template>();
tpl->scale = new_scale;

tpl->center.x = int(center.x*scale_factor+0.5);
tpl->center.y = int(center.y*scale_factor+0.5);

tpl->size.width = int(size.width*scale_factor+0.5);
tpl->size.height = int(size.height*scale_factor+0.5);

tpl->coords.resize(coords.size());
tpl->orientations.resize(orientations.size());
for (size_t i=0;i<coords.size();++i) {
    tpl->coords[i].first = int(coords[i].first*scale_factor+0.5);
    tpl->coords[i].second = int(coords[i].second*scale_factor+0.5);
    tpl->orientations[i] = orientations[i];
}
scaled_templates.push_back(tpl);

return tpl;

}

All uses of Template* should be replaced with std::shared_ptr<Template> and all uses of const Template * with std::shared_ptr< const Template >. Then all the raw delete operations are not necessary, and the matches can be used safely.

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Comments

  • the legacy chamerMatching has been removed entirely in the current api, so that's no more a problem.
  • opencv has cv::Ptr, which does exactly the same as std::shared_ptr (without need for c++11 support)
berak gravatar imageberak ( 2016-08-30 01:10:50 -0500 )edit

It's good to know about cv::Ptr. However, it seems to be lacking std::enable_shared_from_this, and the std::make_shared has better template support for construction of arbitrary objects.

Charles Tallman gravatar imageCharles Tallman ( 2016-08-30 12:52:10 -0500 )edit
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Asked: 2014-02-13 16:21:37 -0500

Seen: 1,467 times

Last updated: Aug 29 '16