Opencv: Undefined reference to cvRound in opencv 3.2

[praneethsusarla]

System information (version)

• OpenCV => 3.2
• Operating System / Platform => linux Ubuntu 16.04 64 Bit
• Compiler => gcc

Detailed description

I have recently installed opencv 3.2 in ubuntu 16.04 system and tried to run a C code using opencv library. The code is not compiling because of the following issue:

/tmp/ccwgquWQ.o: In function `cvPointFrom32f':
try.c:(.text+0x54d): undefined reference to `cvRound'
try.c:(.text+0x563): undefined reference to `cvRound'
/tmp/ccwgquWQ.o: In function `cvReadInt':
try.c:(.text+0xe68): undefined reference to `cvRound'
/tmp/ccwgquWQ.o: In function `cvEllipseBox':
try.c:(.text+0x10d4): undefined reference to `cvRound'
try.c:(.text+0x10f6): undefined reference to `cvRound'
collect2: error: ld returned 1 exit status

I have asked a question related to this in stackoverflow and I got the response saying that, its a bug present in opencv3.2. [http://stackoverflow.com/questions/42918747/yolo-c-compilation-failure-with-debug-1]

The reason for calling it as a bug is as follows:
CvRound function has bee defines in types_c.h in opencv2 whereas in opencv3 its not been defined in types_c.h but in core/fast_math.hpp. Despite being not defined in types_c.h its still being called in types_c.h, core_c.h and imgproc_c.h without any reference to fast_math.hpp

I have tried including the "fast_math.hpp" path (#include core/fast_math.hpp) in types_c.h, core_c.h and imgproc_c.h but it didn't solve the issue.

Kindly, look into this issue and get it resolved as early as possible

[alalek]

run a C code

OpenCV is C++ library. There is no support for direct C compilation, it doesn't work (crash sometimes, see cvGetSize (#6221) problem). Also OpenCV C API is candidate for removal.

You should compile your program as C++ to use OpenCV.

[praneethsusarla]

Thats really strange. There are many implementations in C using CUDA and OpenCV and are popular. What about such implementations then ? eg: YOLO

[chichivica]

Regarding to YOLO specially refer to answer https://stackoverflow.com/a/46808785/2953509