OpenCV Error while building on Raspberry PI

Question

When I use cmake to build opencv-3.2.0 on Raspberry Pi, I encountered a weird error at the 99% of installation.

I did not change anything to not mess anything up, however it seems like a simple code error.

Here is the error appeared in my terminal

/home/pi/opencv-3.2.0/modules/python/src2/cv2.cpp: In function 
‘bool pyopencv_to(PyObject*, T&, const char*) [with T = 
cv::String; PyObject = _object]’:
/home/pi/opencv-3.2.0/modules/python/src2/cv2.cpp:730:34: error: 
invalid conversion from ‘const char*’ to ‘char*’ [-fpermissive]
 char* str = PyString_AsString(obj);
In file included from /home/pi/opencv- 
3.2.0/modules/python/src2/cv2.cpp:1362:

and this is the pyopencv_to function in cv2.cpp

template<>
bool pyopencv_to(PyObject* obj, String& value, const char* name)
{
(void)name;
if(!obj || obj == Py_None)
    return true;
char* str = PyString_AsString(obj);
if(!str)
    return false;
value = String(str);
return true;
}

Should i manually change the code ?

Isn't OpenCV available via pacman on raspbian?

nada
– nada

2019-07-31 12:01:03 +00:00
Commented Jul 31, 2019 at 12:01 — nada
– nada, Commented Jul 31, 2019 at 12:01

Void · Accepted Answer · 2019-09-24 22:40:29Z

1

It appears to be a bug in OpenCV; after I did the following change at opencv3/modules/python/src2/cv2.cpp, it compiled for me. Change...

char* str = PyString_AsString(obj);

to

const char* str = PyString_AsString(obj);

answered Sep 24, 2019 at 22:40

Void

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4 Comments

Nam Vu Over a year ago

Thanks, it's seems to only happens in the rpi from what I've found. Weird, maybe compiler version?

Void Over a year ago

I don't know personally. It could be a version mismatch, but if the fix is simple enough, I just change the codebase.

Nam Vu Over a year ago

Well it's a little more for me since I included this as an ExternalProject_Add in my CMaktLists.txt that way there are no manual installation for different system. I fixed this by creating a diff file and applying the patch with git apply. I'd still like to know why this is okay with other system though o_0. I'm suspecting just different compiler flags/version

Void Over a year ago

ya probably is compiler flags

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