Valgrind 大小为 4 的无效读取（OpenCV）

Posted 2023-02-22

【中文标题】Valgrind 大小为 4 的无效读取（OpenCV）

【英文标题】：Valgrind Invalid read of size 4 (OpenCV)

【发布时间】：2017-02-20 23:17:24

【问题描述】：

这是我的代码：

template <typename TValue>
std::vector<cv::Point2i> GetPixelsWithValue(const cv::Mat& image, const TValue& value) 
    std::vector<cv::Point2i> pixels;
    cv::Size imageSize = image.size();
    for(int i = 0; i < imageSize.height; ++i) 
        for(int j = 0; j < imageSize.width; ++j) 
            if(image.at<TValue>(i, j) == value) 
                cv::Point2i pixel(j, i);
                pixels.push_back(pixel);
            
        
    

    return pixels;

Valgrind 给出这个错误：

==10655== Conditional jump or move depends on uninitialised value(s)
==10655==    at 0x4E88517: GetPixelsWithValue<int>  (OpenCVExtensions.hpp:18)
==10655==    by 0x4E88517: CountPixelsWithValue<int> (OpenCVExtensions.hpp:31)
...
==10655==  Uninitialised value was created by a heap allocation
==10655==    at 0x4C2AB80: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==10655==    by 0x117138EB: cv::fastMalloc(unsigned long) (alloc.cpp:64)
==10655==    by 0x1184F795: cv::StdMatAllocator::allocate(int, int const*, int, void*, unsigned long*, int, cv::UMatUsageFlags) const (matrix.cpp:192)
==10655==    by 0x118507BE: cv::Mat::create(int, int const*, int) (matrix.cpp:426)
==10655==    by 0x4E9BA31: create (mat.inl.hpp:684)
==10655==    by 0x4E9BA31: Mat (mat.inl.hpp:351)
==10655==    by 0x4E9BA31: cv::Mat 
....    
==10655== Invalid read of size 4
==10655==    at 0x4E88510: GetPixelsWithValue<int> (OpenCVExtensions.hpp:18)
....
==10655==  Address 0x23201c92 is 127,346 bytes inside a block of size 127,347 alloc'd
==10655==    at 0x4C2AB80: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==10655==    by 0x117138EB: cv::fastMalloc(unsigned long) (alloc.cpp:64)
 ==10655==    by 0x1184F795: cv::StdMatAllocator::allocate(int, int const*, int, void*, unsigned long*, int, cv::UMatUsageFlags) const (matrix.cpp:192)
==10655==    by 0x118507BE: cv::Mat::create(int, int const*, int) (matrix.cpp:426)
==10655==    by 0x4E9BA31: create (mat.inl.hpp:684)
==10655==    by 0x4E9BA31: Mat (mat.inl.hpp:351)

我发现了这些以及更多：

Why am I getting memory errors when accessing this matrix in OpenCV?

Invalid write size of 4 with matrix class (using valgrind)

但是我不明白为什么会出现错误。这可能是来自 OpenCV 的内部错误吗？

【问题讨论】：

大概你传入的图片一开始就是假的吧？

【参考方案1】：

发现问题。正如@Kerrek SB 指出的那样，图像是问题所在。下面是一个更完整的例子。 uninitialized value 错误似乎是由于尝试使用未初始化的矩阵造成的。我也可能有导致 invalid read 错误的越界索引。

#include "opencv2/highgui/highgui.hpp"
#include <iostream>

using namespace std;
using namespace cv;

std::vector<cv::Point2i> GetPixelsWithValue(const cv::Mat1b& image, const unsigned char& value) 
    std::vector<cv::Point2i> pixels;
    cv::Size imageSize = image.size();
    for(int i = 0; i < imageSize.height; ++i) 
        for(int j = 0; j < imageSize.width; ++j) 
            if(image.at<unsigned char>(i, j) == value) 
                cv::Point2i pixel(j, i);
                pixels.push_back(pixel);
            
        
    

    return pixels;


int main()


    cv::Mat1b image(10, 12);
    image.setTo(0); //enable this and all the uninitialized value errors go away

    image(0,1) = 63;
    image(1,3) = 63;
    image(3,5) = 63;
    image(4,7) = 63;
    image(5,9) = 63;
//    image(10,12) = 63; //causes invalid write error

    std::vector<cv::Point2i> vec = GetPixelsWithValue(image, static_cast<unsigned char>(63));

    std::cout << image(10,12) << std::endl; //bad access. causes invalid read error only
    std::cout << vec.size() << std::endl;

    return 0;