I'm working on opencv implemented codes which I downloaded already by svn. These codes such as SIFT or SURF and codes for opencv were working perfectly before, but suddenly I got this error while I want to compile any code concerns opencv
/usr/lib/gcc/i486-linux-gnu/4.4.3/../../../../lib/crt1.o: In function `_start':
(.text+0x18): undefined reference to `main'
collect2: ld returned 1 exit status
So how can I solve it please, I have red already some problems but they were not helpful with my case, such as I have to change the compilation code from g++ SIFT.cpp -o SIFT .... to g++ -o SIFT SIFT.cpp .... but it didn't work out with me.
Thank you.
I know this is old, but I just had a similar problem (with OpenCV 2.4.4a (and also 2.4.1)) and this was the first thing that popped up on google.
I disabled the "precompiled headers" option in the OpenCV configuration (do it from cmake-gui, or pass -DENABLE_PRECOMPILED_HEADERS=OFF to cmake when generating), and everything works fine.
main is the starting point of execution of any C++ program. And you probably have forgot to build the source file that has main function. Since the file you built doesn't has main, linker failed to find the starting point of execution.
g++ SIFT.cpp fileThatHasMainFunctionDefinition.cpp -o SIFT
or alternatively provide the main in SIFT.cpp itself.
Related
I have started learning C++ on Ubuntu. I am only a few months into using Linux as well.
I am attempting to port over a 2D Ball Collision Script from Javascript to C++ for learning purposes.
I am using simple2D for the drawing in C++: https://github.com/simple2d/simple2d
I go to run this command:
simple2d build c-code-test.cpp
I receive this response:
cc1plus: warning: command line option ‘-std=c11’ is valid for C/ObjC but not for C++
/usr/bin/ld: /tmp/ccl07DBG.o: undefined reference to symbol '_ZNSt8ios_base4InitD1Ev##GLIBCXX_3.4'
//usr/lib/x86_64-linux-gnu/libstdc++.so.6: error adding symbols: DSO missing from command line
collect2: error: ld returned 1 exit status
Due to how fresh I am with Linux and C++ I am unable to make the correct inferences to solve this based on previous questions on stack overflow. I have installed libstdc++6 so I would have though it would be linked correctly.
Can someone walk me through in steps 1, 2, 3 ... Please? Thank you kindly!
The errors you see look to be from trying to compile C++ as C. The command line option is selecting the C11 standard, which is for C, not C++. The missing symbol is because the C++ library isn't being linked in, which also happens when linking a program as C.
I haven't used simple2d, but my guess here is that the compile script they wrote does not support C++ or there is some option you need to use C++. If we look at docs:
The simple2d build command is a helpful shortcut for compiling a
single source file. Of course, you can also use a compiler directly,
for example on Unix-like systems:
cc triangle.c `simple2d --libs` -o triangle
Why don't you try something like their example that invokes the compiler directly. But you would need to use g++ instead of cc. Something like: g++ c-code-test.cpp `simple2d --libs` -o c-code-test
This is a bug with the simple2d script.
They're basically using the wrong build command for C++.
You could work around it by patching in the fix I've linked to, or using the manual build step shown by TrentP.
Or wait for the next version after v1.1.0.
My problem is rather specific, but bear with me.
This in the end is kinda reverse engineering, but this problem in particular seems to fit more this board.
So, I have a shared object compiled for MIPS written in C++. I don't have the source code of the lib. The lib is compiled using GCC 4.3.3. I want to use functions present in this shared object in my amd64 computer running elementary OS. To do this, I used the sourcery cross compiler to cross compile some C++ code to MIPS, that would use this object.
So far I managed this except for this one compile error, which I cannot figure out. The lib is called libdvl.so, and uses as dependency libc.so.0 (and both are in the same folder as the cpp code).
mips-linux-gnu-g++ -g -L/path/to/lib -Wl,-rpath,/path/to/lib -o verifier verifier.cpp -ldvl
which gives me
(...)/mgc/embedded/codebench/bin/../lib/gcc/mips-linux-gnu/4.9.1/../../../../mips-linux-gnu/bin/ld: warning: libc.so.0, needed by /path/to/lib/libdvl.so, may conflict with libc.so.6
(...)/mgc/embedded/codebench/bin/../lib/gcc/mips-linux-gnu/4.9.1/../../../../mips-linux-gnu/bin/ld: errno##GLIBC_PRIVATE: TLS definition in (...)/mgc/embedded/codebench/bin/../mips-linux-gnu/libc/lib/libc.so.6 section .tbss mismatches non-TLS definition in /path/to/lib/libc.so.0 section .bss
/path/to/lib/libc.so.0: error adding symbols: Bad value
collect2: error: ld returned 1 exit status
So I added "-l:libc.so.0" and got this
(...)/mgc/embedded/codebench/bin/../lib/gcc/mips-linux-gnu/4.9.1/../../../../mips-linux-gnu/bin/ld: errno: TLS definition in (...)/mgc/embedded/codebench/bin/../mips-linux-gnu/libc/lib/libc.so.6 section .tbss mismatches non-TLS definition in libc.so.0 section .bss
(...)/mgc/embedded/codebench/bin/../mips-linux-gnu/libc/lib/libc.so.6: error adding symbols: Bad value
collect2: error: ld returned 1 exit status
Any idea how to solve this? I know I am using GCC 4.9.1, but I already downloaded the older code sourcery version which uses GCC 4.3.154 and got the exact same error.
EDIT 1: Exactly as Lol4t0 said, filtered using c++filt it gives an actual function name from stdc++. Using
mips-linux-gnu-g++ -g -L/path/to/lib -Wl,-rpath,/path/to/lib -I/path/to/lib -o verifier verifier.cpp -ldvl -l:libuClibc++.so.0 -l:libutil.so.0 -l:libc.so.0 -l:ld-uClibc.so.0 -nodefaultlibs
to give to libdvl its depencies (as I will not rewrite stdc++ :p), I get the following compile error:
(...)/mgc/embedded/codebench/bin/../lib/gcc/mips-linux-gnu/4.9.1/../../../../mips-linux-gnu/bin/ld: /tmp/cc66DLda.o: undefined reference to symbol '_Unwind_Resume##GCC_3.0'
(...)/mgc/embedded/codebench/bin/../mips-linux-gnu/libc/lib/libgcc_s.so.1: error adding symbols: DSO missing from command line
collect2: error: ld returned 1 exit status
I already confirmed lib dependencies and the order in which they appear.
Any thoughts on this?
Thanks for all the help.
Using -nodefaultlibs solves the first problem though.
You are linking against GLIBC (libc.so.6) and some other libc (libc.so.0).
That could never work: you have to have everything compiled and linked against a single, consistent libc.
Since your libdvl.so uses as dependency libc.so.0, and assuming you can't rebuild libdvl.so, you have to use crosscompiler that targets libc.so.0 (which is possibly dietlibc, or uClibc), and compile and link everything else using that toolchain. Your crosscompiler on the other hand appears to target GLIBC, and will not do you any good.
After a lot of trial and error, you may be able to link the final binary using inconsistent builds, and your binary may even get to main (that is very unlikely). But chances of such binary actually working correctly are minuscule.
I've been trying to figure this out for three days, but I'm quite new to C++ and I seem to have hit a wall.
I want to change one of the opencv source files, particularly the eigenfaces function written by bytefish. I want to have it return many faces instead of one. I believe I figured this part out.
The problem is that, when I recompile opencv, no matter what dll I use, when compiling the demo facial recognition code, I get a couple errors:
SET: IncDir = C:\opencv\build\include
$(INCDIR) = C:\opencv\build\include
SET: LibDir = C:\opencv\build\x86\mingw\lib
$(LIBDIR) = C:\opencv\build\x86\mingw\lib
g++ -I"C:\opencv\build\include" -L"C:\opencv\build\x86\mingw\lib" facerec_eigenfaces.cpp -lopencv_calib3d243 -lopencv_contrib243 -lopencv_core243 -lopencv_features2d243 -lopencv_flann243 -lopencv_gpu243 -lopencv_highgui243 -lopencv_imgproc243 -lopencv_legacy243 -lopencv_ml243 -lopencv_nonfree243 -lopencv_objdetect243 -lopencv_photo243 -lopencv_stitching243 -lopencv_video243 -lopencv_videostab243 -o facerec_eigenfaces
Process started >>>
C:\Users\Nate\AppData\Local\Temp\ccDRRGhr.o:facerec_eigenfaces.cpp:(.text+0x8a0): undefined reference to `cv::createEigenFaceRecognizer(int, double)'
C:\Users\Nate\AppData\Local\Temp\ccDRRGhr.o:facerec_eigenfaces.cpp:(.text+0xdf5): undefined reference to `cv::applyColorMap(cv::_InputArray const&, cv::_OutputArray const&, int)'
collect2: ld returned 1 exit status
<<< Process finished.
SET: Libs = -lopencv_calib3d243 -lopencv_contrib243 -lopencv_core243 -lopencv_features2d243 -lopencv_flann243 -lopencv_gpu243 -lopencv_highgui243 -lopencv_imgproc243 -lopencv_legacy243 -lopencv_ml243(...)
$(LIBS) = -lopencv_calib3d243 -lopencv_contrib243 -lopencv_core243 -lopencv_features2d243 -lopencv_flann243 -lopencv_gpu243 -lopencv_highgui243 -lopencv_imgproc243 -lopencv_legacy243 -lopencv_ml243 -lopen(...)
facerec_eigenfaces
I have seen a couple similar problems, and I have tried implementing all of the methods listed therein, to no avail. This is my first C++ project, so I may be missing something basic, but it looks like by using all of the opencv guides, it builds the contrib dll improperly.
If I need to include anything else here I will. I hate this.
Update
I got this portion of it working. It appears as though I was mixing and matching dll files built with Visual C, with non-visual C built files, which I wouldn't think would matter, but regardless, the code works.
Basically I had been using Notepad++ as my IDE, configured to compile using G++ and MinGW, and then I changed some files with visual C and tried to insert those into my previous project. Then I recompiled with Notepad++ and it would bomb.
So to make it work, I used Visual C as my sole editor. I built it following the instructions from the OpenCV install guide (google), and made my changes only with Visual C. Then I compiled with Visual C too.
I am a C++ newb, so if anyone wants to give a better answer as to what is going on, I'll vote it the best answer.
I'm developing a tool that makes several calls to g++ in order to compile and execute different versions of an original C++ program. More or less, this calls are made inside a loop (it's not a real "loop", but the calls are made inside a function that is part of an iterative algorithm).
For short executions of the algorithm, everything goes smoothly and all the g++ calls finish correctly (I get the binaries ready for its execution). However, the longer the algorithm executions are, the more likely the tool is to crash.
This crashes are due to subsequents crashes of g++ calls, that instead of returning the expected compiled binaries, return the following errors:
Compiling test_oclopts_23_14_6_6000.cpp...
g++ -O3 -L/opt/AMDAPP/lib -lOpenCL -I/opt/AMDAPP/include test_oclopts_23_14_6_6000.cpp -o test_oclopts_23_14_6_6000
/usr/bin/ld: cannot find /usr/lib/i386-linux-gnu/libc_nonshared.a
/usr/bin/ld: cannot find /lib/i386-linux-gnu/ld-linux.so.2
collect2: ld returned 1 exit status
I've googled a bit about this error messages, but I don't understand how they can be applied to my problem: the supposedly missing libraries really are well installed in the system (former g++ calls went OK).
Any idea? Moreover, if you know a better way to compile C++ source code inside a C++ program instead of using system(), I'm accepting suggestions, :)
Thank you so much in advance,
Jorge.
I have been trying to build the logstalgia project (http://code.google.com/p/logstalgia/) on my Mac (10.5). Rather than having to link it to the system libraries correctly, I have built and added all of the dependencies to the project. I am new at this, but I do think I have done this correctly, mostly because I have had two of my friends who are much more experienced say so.
Adding the frameworks removed all of the compile errors, but I still get a linker error. It seems to not be able to find the main() function. I have verified I included main.cpp in the sources to be compiled (using XCode) and that there are no accidental double declarations. I have also verified that the main function is correctly declared (no missing brackets, etc).
It is as though XCode does not link in the correct order. Any help would be really appreciated, I am really excited to be down to a single error! (Hope fixing this does not open a floodgate).
Thanks,
Hamilton
PS - I can definitely provide a zip of the Xcode project if anyone is willing to look!
Checking Dependencies
Ld "/Users/hamiltont/Downloads/logstalgia-0.9.2 2/Untitled/build/Debug/Untitled" normal i386
cd "/Users/hamiltont/Downloads/logstalgia-0.9.2 2/Untitled"
setenv MACOSX_DEPLOYMENT_TARGET 10.5
/developer/usr/bin/g++-4.0 -arch i386 -isysroot /developer/SDKs/MacOSX10.5.sdk "-L/Users/hamiltont/Downloads/logstalgia-0.9.2 2/Untitled/build/Debug" -L/sw/lib "-L/Users/hamiltont/Downloads/logstalgia-0.9.2 2/Untitled/../../pcre-7.9/.libs" -L/opt/local/lib -L/sw/lib "-F/Users/hamiltont/Downloads/logstalgia-0.9.2 2/Untitled/build/Debug" -F/Users/hamiltont/Downloads/logstalgia-0.9.2 -F2/src/SDL.framework "-F/Users/hamiltont/Downloads/logstalgia-0.9.2 2/Untitled" -filelist "/Users/hamiltont/Downloads/logstalgia-0.9.2 2/Untitled/build/Untitled.build/Debug/Untitled.build/Objects-normal/i386/Untitled.LinkFileList" -mmacosx-version-min=10.5 -framework OpenGL -lpcre -lSDL -lSDL_image-1.2.0 -prebind -o "/Users/hamiltont/Downloads/logstalgia-0.9.2 2/Untitled/build/Debug/Untitled"
Undefined symbols:
"_main", referenced from:
start in crt1.10.5.o
ld: symbol(s) not found
collect2: ld returned 1 exit status
I got this error to go away. If I understand, essentially SDL re-names the main function, so that it can do some stuff, then run your application, then clean up. Turns out that if you are building in Xcode, you must use ObjectiveC to compile your application.
In Xcode, telling the linker to try and use SDL_main(), rather than just main() does not work (for some technical reasons that are a bit beyond me). So, you include a few Objective C files. In Oc, you get the benefit of being able to say explicitely what the name of your main class is. Hence, the Objective C files you include seem to do nothing more than let Xcode know to look for SDL_main().
In summary, this really had nothing to do with Logstalgia, but was entirely a problem with getting SDL to link correctly in Xcode. This link is talking about this problem exactly. The SDLMain.h and SDLMain.m are Objective C files. If you can't find them, try googleing "Setting up SDL templates in Xcode." I installed the templates in Xcode, used one of them to create an empty project that would compile, link, and run (and promptly do nothing!) and then I added the project files I wanted to the pre-configured project.
Thanks!
Double-check the link file list to make sure main.cpp's object file is present there:
/Users/hamiltont/Downloads/logstalgia-0.9.2 2/Untitled/build/Untitled.build/Debug/Untitled.build/Objects-normal/i386/Untitled.LinkFileList
You might also want to preprocess the main.cpp to make sure main isn't getting inadvertently renamed (via a rogue macro) or omitted (via a rogue #if).