I'm creating a simple spell checker program with the use of static libraries, as I want other people to be able to use the spell checker functions. The two problem areas are in the library source code and the library header. When I compile the library, this is the error I get:
ar -cvq libspellcheck.a checker.o
a - checker.o
g++ -o spell-check main.o meta.o libspellcheck.a
libspellcheck.a(checker.o): In function `check_spelling(char*, char*)':
checker.cpp:(.text+0x0): multiple definition of `check_spelling(char*, char*)'
libspellcheck.a(checker.o):checker.cpp:(.text+0x0): first defined here
collect2: ld returned 1 exit status
make: *** [spellcheck] Error 1
The checker.cpp code is located here.
The header file (spellcheck.h) is located here.
What I would like to know is what is causing the errors above, as I can't figure it out.
It looks as though you've added checker.cpp to the archive twice.
Try using this command instead:
ar -cvr libspellcheck.a checker.o
Using r instead of q will replace any existing file with the same name, rather than adding another copy of it.
Alternatively, just ensure you delete the archive before you add any files to it, so it always starts empty.
The problem seems to be linking checker.cpp twice - can you add your makefiles (also make sure check_spelling isn't defined twice in checker.cpp and try to clean the intermediary files before build)?
Related
I am working with the windows.h functions and everything works fine so far.
But when I try to use functions which require me to link external libraries something goes wrong.
In this case I am trying to use CreateFont(). I already know that I must link libwinmm.a and libgdi32.a and I've done that:
See this screenshot
But when I try to build the project i get following error messages:
g++ "-LD:\\Programme\\Eclipse\\lib" -o GameTest.exe "src\\choosemealmain.o" "src\\mealchooser.o" "-lD:\\Programme\\Eclipse\\lib\\libwinmm.a" "-lD:\\Programme\\Eclipse\\lib\\libgdi32.a"
d:/programme/eclipse/bin/../lib/gcc/mingw32/6.3.0/../../../../mingw32/bin/ld.exe: cannot find -lD:\Programme\Eclipse\lib\libwinmm.a
d:/programme/eclipse/bin/../lib/gcc/mingw32/6.3.0/../../../../mingw32/bin/ld.exe: cannot find -lD:\Programme\Eclipse\lib\libgdi32.a
collect2.exe: error: ld returned 1 exit status
I made sure to doublecheck whether the mentioned libraries are actually to be found in the mentioned path and they are.
I would be glad for any kind of help!
You are wrongly using quotes with -l flag. The -l flag also automatically adds the lib prefix and the .a extension. Your command line should be:
g++ -LD:\Programme\Eclipse\lib -o GameTest.exe "src\choosemealmain.o" "src\mealchooser.o" -lwinmm -lgdi32
I have a strange problem linking c++ with Leptonica. Normal function invocation works fine, but I need functions from the library which were originally not exposed in the .so library. So I have searched for the two interesting functions in the source, removed the static keyword, so they look similar to exposed ones. I have remade the full library after a make clean. The .so file looks OK:
nm liblept.so.5.0.0
...
000000000009d010 T dewarpGetMeanVerticals
000000000009d160 T dewarpGetTextlineCenters
000000000009d8f0 T dewarpIsLineCoverageValid
Compiling to .o file and observing it:
g++ -c -std=c++11 -I../leptonica/src/src/ preproc.cpp -L../leptonica/src/.libs/ -llept -o preproc
nm preproc
...
U dewarpGetMeanVerticals
U dewarpIsLineCoverageValid
While the same compiling without -c flag results in
/tmp/ccCPqS1R.o: In function `_dewarpGetTextlineCenters(Pix*, int)':
preproc.cpp:(.text+0x3d5): undefined reference to `dewarpGetMeanVerticals'
/tmp/ccCPqS1R.o: In function `_dewarpBuildPageModel(L_Dewarp*, char const*)':
preproc.cpp:(.text+0x81d): undefined reference to `dewarpIsLineCoverageValid'
collect2: error: ld returned 1 exit status
What do I do wrong?
Thank you in advance: Balázs
I think you may need the extern "C" keywords around those functions if you want to expose them in the so. Since the names don't appear to be mangled by the C++ compiler in the .so this is probably not the case.
I notice that you're showing us what's in liblept.so.5.0.0 and linking against liblept.so. Is it possible that you need to update a symbolic link so that you're linking against the correct .so file?
I tried to run .c file called grover.c in this C application libquantum
www.libquantum.de/files/libquantum-1.1.1.tar.gz
Now I this application already contains a Makefile.in and I can generate the executables called shor and grover using the command
./configure
make
make demos
But when I try to run grover.c using gcc or clan like this
clang grover.c
It gives me error of lots of undefined function reference.
In function oracle':
grover.c:(.text+0x50): undefined reference toquantum_sigma_x'
grover.c:(.text+0x89): undefined reference to quantum_toffoli'
grover.c:(.text+0xc8): undefined reference toquantum_toffoli'
grover.c:(.text+0xf2): undefined reference to quantum_cnot'
grover.c:(.text+0x137): undefined reference toquantum_toffoli'
grover.c:(.text+0x16b): undefined reference to quantum_toffoli'
grover.c:(.text+0x1b0): undefined reference toquantum_sigma_x'
I need to know how can I remove this error and if I can run this c code called grover.c in this application.
Thanks,
It looks like your compiler can not find one or more libraries to link to. My hunch is that the makefile has the appropriate commands to invoke the linker.
If you look at your makefile, you probably will see some commands like -L -l,
when the flag -L add a directory to the default search path for libraries and the flag -l is used to name the library to link.
for example -L/lib/openGL -lglut32 would cause the library libglut32.so.X.Y.Z which is found in the directory /lib/openGL. (not this is for a Linux system, but it should be fairly similar for Mac).
N.B. X.Y.Z are the version number of the library.
Once you work this out, there may be issues with the load finding the libraries, especially if they are in non-standard locations.
------------------------ edit --------------------------
After I posted this, and went to bed I realized that I missed a potential case (and thanks to Paul Griffiths for also noticing my omission.....teach me to do multiple things at once).
Any how, just compiling a simple file, say hello.c, as clang hello.c -o hello works because everything is in one file and clang will automatically link to the C run-time library.
If, in your case the code is spread across multiple files, say grover.c and file1.c you would need to do:
clang -c grover.c -o grover.o
clang -c file1.c -o file1.o
clang grover.o file1.o -o grover
(or alteratively clang grover.c file1.c -o grover)
SO what the first two lines are doing is translating the source-code files (grover.c and file1.c) into object files. THe third line covers the two object files into an executable.
Finally, both these cases can be involved. You could have multiple files as well as missing libraries.
I'm currently learning OpenCL. Now, when I want to compile my program, I get an error with this command:
g++ -Wall -l OpenCL main.cpp -o main
The errors are mostly undefined references, because the library is not linked, I think (nevertheless I will post the error code at the end).
But with this command everything works fine:
g++ -Wall main.cpp -o main -l OpenCL
So my question is, what do I have to do, to use the -l Flag in front of the command?
(The Background is: I want to use Netbeans to compile my programm and when i add the flag under -> properties -> build -> C++ Compiler -> additional options, it will put in in the Position, shown in the first command)
Thanks in advance for your help
Here's the error code:
/tmp/ccmKP4oI.o: In function `cl::detail::ReferenceHandler<_cl_context*>::release(_cl_context*)':
main.cpp:(.text._ZN2cl6detail16ReferenceHandlerIP11_cl_contextE7releaseES3_[_ZN2cl6detail16ReferenceHandlerIP11_cl_contextE7releaseES3_]+0x14): undefined reference to `clReleaseContext'
/tmp/ccmKP4oI.o: In function `cl::detail::ReferenceHandler<_cl_command_queue*>::release(_cl_command_queue*)':
main.cpp:(.text._ZN2cl6detail16ReferenceHandlerIP17_cl_command_queueE7releaseES3_[_ZN2cl6detail16ReferenceHandlerIP17_cl_command_queueE7releaseES3_]+0x14): undefined reference to `clReleaseCommandQueue'
/tmp/ccmKP4oI.o: In function `cl::Platform::getInfo(unsigned int, std::string*) const':
main.cpp:(.text._ZNK2cl8Platform7getInfoEjPSs[_ZNK2cl8Platform7getInfoEjPSs]+0x22): undefined reference to `clGetPlatformInfo'
/tmp/ccmKP4oI.o: In function `cl::Platform::get(std::vector<cl::Platform, std::allocator<cl::Platform> >*)':
main.cpp:(.text._ZN2cl8Platform3getEPSt6vectorIS0_SaIS0_EE[_ZN2cl8Platform3getEPSt6vectorIS0_SaIS0_EE]+0x41): undefined reference to `clGetPlatformIDs'
main.cpp:(.text._ZN2cl8Platform3getEPSt6vectorIS0_SaIS0_EE[_ZN2cl8Platform3getEPSt6vectorIS0_SaIS0_EE]+0xb4): undefined reference to `clGetPlatformIDs'
collect2: error: ld returned 1 exit status
Order of [most] arguments to g++ is very important.
Libraries should go last (at least after source and object files). You can't really change that.
The -l should preferably be glued to the library name:
g++ -Wall main.cpp -o main -lOpenCL
# ^^^ glue the -l to the library name
You probably want to also pass -g (in addition of -Wall) to the compiler to get a debuggable binary. Use the gdb debugger.
As James Kanze commented, you might want to replace -g with -ggdb if using specifically gdb.
With g++ (and generally under Unix), -l specifies a source of
input (either a .a or a .so), and input is processed in
order. When the input is a static library (a .a file), it
will be scanned for objects which resolve undefined references;
if it is a .so, there aren't any object files in it, but it
will still only be taken into consideration if it resolves some
undefined symbol.
When you put the -l before any object files, there are no
undefined symbols yet, so nothing will be incorporated into the
program.
I have written some code in Lib_file.h and Lib_file.cpp. I wish to convert this code to a static library. I am able to compile the code (using the command g++ -I <necessary include files> -o Lib_file.o Lib_file.cpp)to get Lib_file.o. I am also able to add it to an archive using the ar rvs Lib_file.a Lib_file.o command. Now when I try to use this library in some other code using the -L option, I get undefined reference errors. This errors point to the code in my Lib_file.o . So my question is how do I get the code in my Lib_file.cpp to link to the libraries that it uses.
I have tried the following options so far
I. After creating the Lib_file.o, I tried the following command
g++ -L<include path> -l<.a files> Lib_file.o . On executing this command, I get the following error
/usr/lib/../lib64/crt1.o: In function `_start':
init.c:(.text+0x20): undefined reference to `main'
collect2: ld returned 1 exit status
II. I tried to include all the necessary .a files in a new archive along with my Lib_file.o using the ar command. Still I get the undefined reference error when I try to use the Lib_file.a library with my application
Please help me out here
First of all, all libraries are normally named something like libxyz.a where xyz is the name of the library.
Secondly, you try to create a program using only the object file you used for the library, and also linking it with itself. This will of course not work, since the library have no main function which is needed for normal programs. You have to create another program, and link that one with the library.
Like
gcc myotherprogram.c -o myotherprogram -L/some/path -lxyz
As you can see in my command line above, I placed the library last on the command line. It's needed because the linker look for dependencies in kind of reversed order.
Edit: Linking your static library with other libraries: You don't. A static library is completely standalone, and if it needs other libraries itself to work then they have to be present on the command line when compiling the actual program.
For example, lets say that library xyz depends on the standard math library (i.e. the m library). You can't "link" with it when creating the xyz library as you don't actually link static libraries, you just put a collection of object files together in an archive (ar and the .a extension is for archive). When you build the actual application that needs the xyz library you also needs to link with whatever libraries that xyz needs:
gcc myotherprogram.c -o myotherprogram -L/some/path -lxyz -lm