vlc FTBFS with opencv-3.4.1 #10963

chris2553 · 2018-02-28T14:10:29Z

System information (version)

OpenCV => 3.4.1
Operating System / Platform => Linux
Compiler => gcc-7-20180222 (a 7.3.1 snapshot)

vlc-3.0.1 fails to build against opencv-3.4.1, because the C compiler produces and error at line 485 of /usr/include/opencv2/core/cvdef.h. The error message is:

           /usr/include/opencv2/core/cvdef.h:485:1: error: unknown type name 'namespace'

This is because the C compiler is trying to compile C++ code.

Steps to reproduce

build and install opencv-3.4.1
configure vlc-3.0.1 to include opencv and then run make

Proposed fix

The following patch to opencv allows the build of vlc to complete:

--- opencv-3.4.1/modules/core/include/opencv2/core/cvdef.h.orig	2018-02-28 10:16:45.000320632 +0000
+++ opencv-3.4.1/modules/core/include/opencv2/core/cvdef.h	2018-02-28 10:34:30.852346927 +0000
@@ -454,6 +454,7 @@ Cv64suf;
 
 
 // Integer types portatibility
+#if defined __cplusplus
 #ifdef OPENCV_STDINT_HEADER
 #include OPENCV_STDINT_HEADER
 #else
@@ -494,6 +495,9 @@ typedef ::uint64_t uint64_t;
 }
 #endif
 #endif
+#else
+#include <stdint.h>
+#endif
 
 
 //! @}

With the patched opencv installed, I have also built the frei0r-plugin-1.6.0, gstreamer-plugins-bad-1.12.4 and LiVES-2.8.7, all of which use opencv (although I don't know whether they failed against an unpatched version)

The text was updated successfully, but these errors were encountered:

alalek · 2018-02-28T14:38:28Z

OpenCV 3.x doesn't not support C compilation mode officially. There are still legacy C API calls (from OpenCV 1.x) but they should be compiled in C++ compilation mode.
Even if you succeeded to build code with C compiler (and avoid cvRound problem: #6585) it would lead to terrible behavior like #6221 or silent crashes in case of raised C++ exceptions.
All new algorithms in OpenCV are written in C++, so there are no benefits to use OpenCV 3.x in C programs.

Good solution for C programs is FFI C bindings, but we don't have them (see some discussion here).

chris2553 · 2018-02-28T20:28:27Z

Thanks, Alexander.

On 28/02/18 14:43, Alexander Alekhin wrote: OpenCV 3.x doesn't not support C compilation mode officially. There are still legacy C API calls (from OpenCV 1.x) but they should be compiled in C++ compilation mode. Even if you succeeded to build code with C compiler (and avoid cvRound problem: #6585 <#6585>) it would lead to terrible behavior like #6221 <#6221> or silent crashes in case of raised C++ exceptions. All new algorithms in OpenCV are written in C++, so there are no benefits to use OpenCV 3.x in C programs.

Ah, right. I was misled by the second sentence on opencv.org - "It has C++, C, Python and Java interfaces and supports Windows, Linux, Mac OS, iOS and Android." I guess that doesn't actually conflict with what you say, but that's only because it's a rather general statement :-) Does 2.x support C compilation and, if not, what's the latest version that does, please?

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alalek · 2018-02-28T20:46:52Z

OpenCV 2.4.x has some chance to work properly, but we don't run "native C" tests anymore.

AdamWill · 2018-03-05T20:55:33Z

This also breaks libfreenect, FWIW:

https://koji.fedoraproject.org/koji/taskinfo?taskID=25506808

I'll look at whether libfreenect can/should be building for C++ not C.

jiapei100 · 2018-03-09T02:44:20Z

Trying to build the most recent mrpt, this issue persists...
It looks highgui also has some problem?

[ 53%] Building CXX object libs/vision/CMakeFiles/mrpt-vision.dir/src/faster/faster_corner_9.cpp.o
In file included from /usr/local/include/opencv2/core/core_c.h:48:0,
                 from /media/jiapei/Data/Downloads/robotics/mrpt/mrpt/libs/img/include/mrpt/otherlibs/do_opencv_includes.h:27,
                 from /media/jiapei/Data/Downloads/robotics/mrpt/mrpt/libs/vision/src/sift-hess/utils.h:15,
                 from /media/jiapei/Data/Downloads/robotics/mrpt/mrpt/libs/vision/src/sift-hess/utils.c:10:
/usr/local/include/opencv2/highgui/highgui_c.h:139:1: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘:’ token
 CVAPI(cv::Rect)cvGetWindowImageRect(const char* name);
 ^
In file included from /usr/local/include/opencv2/core/core_c.h:48:0,
                 from /media/jiapei/Data/Downloads/robotics/mrpt/mrpt/libs/img/include/mrpt/otherlibs/do_opencv_includes.h:27,
                 from /media/jiapei/Data/Downloads/robotics/mrpt/mrpt/libs/vision/src/sift-hess/sift.h:15,
                 from /media/jiapei/Data/Downloads/robotics/mrpt/mrpt/libs/vision/src/sift-hess/sift.c:10:
/usr/local/include/opencv2/highgui/highgui_c.h:139:1: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘:’ token
 CVAPI(cv::Rect)cvGetWindowImageRect(const char* name);
 ^
In file included from /usr/local/include/opencv2/core/core_c.h:48:0,
                 from /media/jiapei/Data/Downloads/robotics/mrpt/mrpt/libs/img/include/mrpt/otherlibs/do_opencv_includes.h:27,
                 from /media/jiapei/Data/Downloads/robotics/mrpt/mrpt/libs/vision/src/sift-hess/utils.h:15,
                 from /media/jiapei/Data/Downloads/robotics/mrpt/mrpt/libs/vision/src/sift-hess/imgfeatures.c:10:
/usr/local/include/opencv2/highgui/highgui_c.h:139:1: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘:’ token
 CVAPI(cv::Rect)cvGetWindowImageRect(const char* name);
 ^
/media/jiapei/Data/Downloads/robotics/mrpt/mrpt/libs/vision/src/sift-hess/sift.c: In function ‘dominant_ori’:
/media/jiapei/Data/Downloads/robotics/mrpt/mrpt/libs/vision/src/sift-hess/sift.c:909:6: warning: variable ‘maxbin’ set but not used [-Wunused-but-set-variable]
  int maxbin, i;
      ^
libs/vision/CMakeFiles/mrpt-vision.dir/build.make:231: recipe for target 'libs/vision/CMakeFiles/mrpt-vision.dir/src/sift-hess/imgfeatures.c.o' failed
make[2]: *** [libs/vision/CMakeFiles/mrpt-vision.dir/src/sift-hess/imgfeatures.c.o] Error 1
make[2]: *** Waiting for unfinished jobs....
libs/vision/CMakeFiles/mrpt-vision.dir/build.make:244: recipe for target 'libs/vision/CMakeFiles/mrpt-vision.dir/src/sift-hess/sift.c.o' failed
make[2]: *** [libs/vision/CMakeFiles/mrpt-vision.dir/src/sift-hess/sift.c.o] Error 1
libs/vision/CMakeFiles/mrpt-vision.dir/build.make:257: recipe for target 'libs/vision/CMakeFiles/mrpt-vision.dir/src/sift-hess/utils.c.o' failed
make[2]: *** [libs/vision/CMakeFiles/mrpt-vision.dir/src/sift-hess/utils.c.o] Error 1
CMakeFiles/Makefile2:2400: recipe for target 'libs/vision/CMakeFiles/mrpt-vision.dir/all' failed
make[1]: *** [libs/vision/CMakeFiles/mrpt-vision.dir/all] Error 2
Makefile:162: recipe for target 'all' failed
make: *** [all] Error 2

Can anybody give some further suggestions ?
Thank you very much
Pei

sergiomb2 · 2018-03-15T02:55:24Z

After update to libfreenect-0.5.7 it built well
php-facedetect also it built well after this commit [1], conclusion we need report it in VLC project

[1]
infusion/PHP-Facedetect@c717941

Required for OpenCV 3.4.1 or later; strongly recommended for older versions >= OpenCV 2. See opencv/opencv#10963. This doesn't build yet -- the filter uses reserved C++ keywords (`class`) and it needs additional casts.

sjuxax · 2018-03-19T13:38:13Z

Raised on the ffmpeg-devel mailing list at http://ffmpeg.org/pipermail/ffmpeg-devel/2018-March/226872.html .

tensor-flower · 2018-03-27T10:23:13Z

Proposed fix by chris2553 worked for me. I'm 3.4.1-dev.

chris2553 · 2018-03-27T18:29:21Z

On 27/03/18 11:23, Guo Wanqi wrote: Proposed fix by chris2553 worked for me. I'm 3.4.1-dev.

ISTR that there was concern that, whilst my patch allowed the build to complete, the application may not work properly. Why that may be the case is beyond my technical knowledge. C++ is a ragbag of bewildering traps to me :-) Chris

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StevenPuttemans · 2018-04-05T09:00:44Z

Actually I arrived here when hitting similar problems re-installing the darknet framework (our own version). It works just fine by returning to 3.4.0, which given the limited stuff darknet uses from OpenCV works, but to me that shows that we changed something drastically in the switch from 3.4.0 to 3.4.1-dev. Any way of reverting those changes and identifying how we can circumvent this?

AdamWill · 2018-04-05T16:57:20Z

@StevenPuttemans: the immediate change was c020a7b ; that code is not C compatible, it assumes namespace support. So you can revert things to the status of 3.4.0 by just patching an #if defined __cplusplus around that change, exactly as the initial report here says.

But given what @alalek wrote in this comment, it seems unwise to just do that and go on pretending that OpenCV is C compatible when it really isn't. Which is why no-one's really suggesting we push that change upstream any more, and instead look at changing what downstreams expect of OpenCV.

NCBee · 2018-04-06T05:54:46Z

I beg to differ. Granted that OpenCV is first and foremost a C++ library, but why introduce a patch that breaks multiple downstream projects (in my case ffmpeg) just to prove a point? What is so hard about putting a __cplusplus guard around a "newly introduced functionality"? If we are not supporting C but keeping the legacy code, then why even touch the C headers that previously worked for downstream projects?

This issue cost me 4 hours to debug, whereas it would have cost someone 10 seconds to write the guard in the first place, or just leave the legacy code alone.

StevenPuttemans · 2018-04-06T08:39:48Z

@AdamWill I have to agree with @NCBee here. OpenCV has always ensured backwards compatibility. Although not actively ensuring a working C-API they have been keeping it alive just because so many downstream projects tend to use this API.

In my opinion it is a bad programming habbit to provide C++ - directives in C - headers. The convention is that if you provide a *.c or *.h file that it should be compiling perfectly fine using gcc. So either OpenCV should drop the deprecated C-headers (and in the process make more people angry), or follow general conventions.

swills · 2018-04-28T19:41:47Z

I also encountered this issue. Any chance of getting it resolved?

swills · 2018-04-30T13:25:22Z

This page:

https://docs.opencv.org/3.4.1/db/dfa/tutorial_transition_guide.html#tutorial_transition_hints_headers

Seems to imply the .h files should be usable with a non-C++ compiler.

AdamWill · 2018-04-30T15:00:08Z

Tutorials and docs are kind of notorious for not being kept entirely up to date. An explicit statement that this is not really the case any longer by one of the developers would seem to trump that.

There is a know upstream ffmpeg compile error when enabling libopencv. It should compile opencv code in C++ mode but it is compiling in C mode. Disabling libopencv support while a fix is not provided either by upstream ffmpeg or by opencv repository package. References: ----------- http://trac.ffmpeg.org/ticket/7059 opencv/opencv#10963 https://bugs.archlinux.org/task/57811

opencv support was disabled[1] a long time ago because ffmpeg failed to build with it. opencv 3.x does not support C compilation mode[2] anymore, and ffmpeg uses only C. There is no ffmpeg interest[3] in compiling opencv in C++ mode, so opencv2 must be used here. References ---------- [1] https://aur.archlinux.org/cgit/aur.git/commit/?h=ffmpeg-full&id=5d72306579c20bc36ff7c6ff1005b168e3b263de [2] opencv/opencv#10963 [3] https://trac.ffmpeg.org/ticket/7059

opencv support was disabled[1] a long time ago because ffmpeg failed to build with it. opencv 3.x does not support C compilation mode[2] anymore, and ffmpeg uses only C. There is no ffmpeg interest[3] in compiling opencv in C++ mode, so opencv2 must be used here. References ---------- [1] https://aur.archlinux.org/cgit/aur.git/commit/?h=ffmpeg-full-git&id=f9d589fa30dddc8318fff742a87b7927566b2a9e [2] opencv/opencv#10963 [3] https://trac.ffmpeg.org/ticket/7059

Pzixel mentioned this issue Feb 28, 2018

WIP: Feature/submodules nebgnahz/cv-rs#66

Closed

This was referenced Mar 1, 2018

Error during make with Opencv=1 .. pjreddie/darknet#502

Open

Compiling error for darknet with OCV 3.4.1: (cvdef.h) unknown type name ‘namespace’ AlexeyAB/darknet#414

Open

This was referenced Mar 5, 2018

OpenCV and/or Python wrapper (when using OpenCV) fails to build against opencv 3.4 OpenKinect/libfreenect#553

Closed

OpenCV 3.x explicitly does not support pure C compilation, build fails with 3.4+ kliment/simarrange#15

Open

tomoaki0705 mentioned this issue Mar 8, 2018

error: unknown type name ‘namespace’ #11036

Closed

AdamWill mentioned this issue Mar 8, 2018

build: portable integer types #10883

Merged

AlexeyAB mentioned this issue Mar 8, 2018

not support lastest cuda 9.0 and cudnn7 pjreddie/darknet#278

Open

TheMikeyR mentioned this issue Mar 9, 2018

OpenCV visualization error pjreddie/darknet#518

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sjuxax mentioned this issue Mar 18, 2018

need solution for "libopencv not found" facebook/transform360#56

Open

AlexeyAB mentioned this issue Mar 24, 2018

Syntax errors in C librarys when trying to compile with VS2015, WIN10 AlexeyAB/darknet#500

Closed

MaeThird mentioned this issue Mar 26, 2018

Error from "make" when enabling OpenCV 3 pjreddie/darknet#551

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AlexeyAB mentioned this issue Apr 17, 2018

Thousands of Compiler Errors on Visual Studio 2015 for darknet.sln AlexeyAB/darknet#645

Open

AlexeyAB mentioned this issue Apr 27, 2018

Error while compiling darknet with opencv=1 AlexeyAB/darknet#709

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pjreddie mentioned this issue May 1, 2018

Fix some issues with C API #11431

Closed

saudet mentioned this issue May 18, 2018

error: (-215) (flags & FIXED_TYPE) != 0 in function type when crop jpg bytedeco/javacv#998

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This was referenced May 28, 2018

build: workaround issues with C compilation mode #11605

Merged

Problems with C API in OpenCV 3.4.1 #10969

Closed

albertwujj mentioned this issue Jun 14, 2018

Cant make the YOLO when OPENCV=1 Ubuntu 17.10 pjreddie/darknet#485

Open

joshuajnoble mentioned this issue Jul 26, 2018

Clarification on which version of OpenCV AlexeyAB/darknet#1280

Open

karolmajek mentioned this issue Mar 29, 2019

Error when building with OpenCV 3.4 leggedrobotics/darknet_ros#133

Closed

alalek mentioned this issue Dec 9, 2019

The headers cannot be included using a C-compiler #16108

Closed

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vlc FTBFS with opencv-3.4.1 #10963

vlc FTBFS with opencv-3.4.1 #10963

chris2553 commented Feb 28, 2018 •

edited by alalek

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vlc FTBFS with opencv-3.4.1 #10963

vlc FTBFS with opencv-3.4.1 #10963

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