When I execute this command
g++ -L/home/andrea/Desktop/cppTest/Test1/myLib -I/home/andrea/Desktop/cppTest/Test1/commons -lNames compiledObjects/SayHello.o -o SayHello
The compiler return this error:
/usr/lib64/gcc/x86_64-suse-linux/4.8/../../../../x86_64-suse-linux/bin/ld: cannot find -lNames
collect2: error: ld returned 1 exit status
Why the compiler search "Names" here
/usr/lib64/gcc/x86_64-suse-linux/4.8/../../../../x86_64-suse-linux/bin/ld
instead of
/home/andrea/Desktop/cppTest/Test1/myLib
That is the path specified using -L argmunt?
Problem found
The real problem was that I've forgotten to name the library in this way libName.so
The right syntax is as follows
g++ -I/home/andrea/Desktop/cppTest/Test1/commons compiledObjects/SayHello.o -o SayHello -L/home/andrea/Desktop/cppTest/Test1/myLib -lNames
(i.e. -L and -l options at the end).
And ensure that the directory /home/andrea/Desktop/cppTest/Test1/ contains the library libNames.so.
Related
I am attempting to use the libtommath library. I'm using the NetBeans IDE for my project on Ubuntu linux. I have downloaded and built the library, I have done a 'make install' to put the resulting .a file into /usr/lib/ and the .h files into /usr/include
It appears to be finding the files appropriately (since I no longer get those errors, which I did before installing into the /usr directories).
However, when I create a simple main making a call to mp_init (which is in the library), I get the following error when I attempt to make my project:
mkdir -p build/Debug/GNU-Linux-x86
rm -f build/Debug/GNU-Linux-x86/main.o.d
gcc -c -g -MMD -MP -MF build/Debug/GNU-Linux-x86/main.o.d -o build/Debug/GNU-Linux-x86/main.o main.c
mkdir -p dist/Debug/GNU-Linux-x86
gcc -o dist/Debug/GNU-Linux-x86/cproj1 build/Debug/GNU-Linux-x86/main.o
build/Debug/GNU-Linux-x86/main.o: In function 'main':
/home/[[myusername]]/NetBeansProjects/CProj1/main.c:18: undefined reference to `mp_init'
collect2: ld returned 1 exit status
make[2]: *** [dist/Debug/GNU-Linux-x86/cproj1] Error 1
So, it looks like the linker can't find the function within the library, however it IS there, so I just don't know what could be causing this.
I get the same error if I type the gcc command directly and skip the makefile, I also made sure the static library got compiled with gcc as well.
Edited to Add:
I get these same errors if I do the compile directly and add the library with -l or -L:
$ gcc -l /usr/lib/libtommath.a main.c
/usr/bin/ld: cannot find -l/usr/lib/libtommath.a
collect2: ld returned 1 exit status
$ gcc -llibtommath.a main.c
/usr/bin/ld: cannot find -llibtommath.a
collect2: ld returned 1 exit status
$ gcc -Llibtommath.a main.c
/tmp/ccOxzclw.o: In function `main':
main.c:(.text+0x18): undefined reference to `mp_init'
collect2: ld returned 1 exit status
$ gcc -Llibtommath.a main.c
/tmp/ccOxzclw.o: In function `main':
main.c:(.text+0x18): undefined reference to `mp_init'
collect2: ld returned 1 exit status
I am very rusty on this stuff, so I'm not sure I'm using the right command here, in the -L examples are the libraries being found? If the library isn't being found how on earth do I get it to find the library? It's in /usr/lib, I've tried it with the .a file in the current directory, etc. Is there an environment variable I need to set? If so, how, etc.
I've tried a completely different library (GMP) and had the EXACT same problem. This has got to be some kind of Ubuntu environment issue? Anyone have any idea how to fix this?
The trick here is to put the library AFTER the module you are compiling. The problem is a reference thing. The linker resolves references in order, so when the library is BEFORE the module being compiled, the linker gets confused and does not think that any of the functions in the library are needed. By putting the library AFTER the module, the references to the library in the module are resolved by the linker.
Yes, It is required to add libraries after the source files/objects files. This command will solve the problem:
gcc -static -L/usr/lib -I/usr/lib main.c -ltommath
If the .c source files are converted .cpp (like as in parsec), then the extern needs to be followed by "C" as in
extern "C" void foo();
I am trying to link a project with the following command:
g++ build/test.o -o bin/test -pthread -L lib -L /home/alexander/opt/lib -lboost_thread-mt
which results in the following errors:
/usr/bin/ld: cannot find -lboost_thread-mt
collect2: error: ld returned 1 exit status
However, the boost libraries are installed in the directory /home/alexander/opt/lib. Why does the linker do not find the boost libraries? I also tried to link with -I instead if -L with the same outcome...
Content of /home/alexander/opt/lib is /home/alexander/opt/lib/boost_1_57_0.
change libboost_thread-mt to libboost_thread, first find the address of libboost_thread.so and libboost_thread.a then make softlinks to these files in the same address,
so it should be:
ln -s /...libboostSourceFiles.../libboost_thread.so /..RequestTOmtFiles.../libboost_thread-mt.so
it works for other libboost -mt files too, like serialization , iostreams, programoptions
I'm busy trying to compile and link a c++ program using the following make file
driver.so:driver.cpp
g++ -c driver.cpp -o driver.so
g++ -L/tokenlib/libtokenlib.so driver.so -o linked
but I'm getting the error
g++ -c driver.cpp -o driver.so
g++ -L/tokenlib/libtokenlib.so driver.so -o linked
driver.so: In function `main':
driver.cpp:(.text+0x9): undefined reference to `tokenlib::acquire_token()'
collect2: error: ld returned 1 exit status
make: *** [driver.so] Error 1
and my file hierarchy is
/root
makefile
driver.cpp
/tokenlib
libtokenlib.so
I've been told that adding -Wl,-rpath=./tokenlib to my g++ arguements would solve the problem so I tried like this
driver.so:driver.cpp
g++ -c driver.cpp -o driver.so -Wl,-rpath=./tokenlib
g++ -L/tokenlib/libtokenlib.so driver.so -o linked -Wl,-rpath=./tokenlib
but it still isn't working.
I'm a complete novice and any help would be appreciated.
The linker usually refers to .a (stub) libraries, not to .so files!
-L options specify the paths, the lnker should take in account.
The -l<mystuff> option tries to resolve a library named libmystuff.a from any of the given path's of the -L options, or compiler intrinsic library search paths.
I created a .so file and put it in the location /opt/lib and added this path to LD_LIBRARY_PATH now after this when I try to compile my main program with the following command:
g++ -Wall -I/home/alwin/Development/Calculator/ main.cpp -lcalc -o calculator
I get the following error:
/usr/bin/ld: cannot find -lcalc
collect2: ld returned 1 exit status
Can someone help me with this.
I created the shared library using the code blocks IDE
Add -L/opt/lib to your compiler parameters, this makes the compiler and linker search that path for libcalc.so in that folder.
When you make the call to gcc it should say
g++ -Wall -I/home/alwin/Development/Calculator/ -L/opt/lib main.cpp -lcalc -o calculator
not -libcalc.so
I have a similar problem with auto-generated makes.
You can create a soft link from your compile directory to the library directory.
Then the library becomes "local".
cd /compile/directory
ln -s /path/to/libcalc.so libcalc.so
You need to add -L/opt/lib to tell ld to look there for shared objects.
#Alwin Doss
You should provide the -L option before -l. You would have done the other way round probably. Try this :)
export LDFLAGS=-L/path to lib/ this will solve the error
I'm trying to use the Boost Libraries ... but to no avail. I attempted to follow the Getting Started tutorial on Boost's website (for Unix Variants), but having problems along the way.
I compiled the libraries into a directory in my Downloads folder:
/Users/myUsername/Downloads/boostCompiled
When I use the full path to the library ... The example program (given on the Boost Website) compiles and links fine.
g++ -o boostTesting boostTesting.cpp -I /Users/myUsername/Downloads/boostCompiled/include/ /Users/myUsername/Downloads/boostCompiled/lib/libboost_regex.a
However, when I attempt to link the using the -L and -l options ... it fails ...
g++ -o boostTesting boostTesting.cpp -I /Users/myUsername/Downloads/boostCompiled/include/ -L /Users/myUsername/Downloads/boostCompiled/lib/ -l boost_regex
ld: library not found for -lboost_regex
collect2: ld returned 1 exit status
g++ -o boostTesting boostTesting.cpp -I /Users/myUsername/Downloads/boostCompiled/include/ -L /Users/myUsername/Downloads/boostCompiled/lib/ -l libboost_regex
ld: library not found for -llibboost_regex
collect2: ld returned 1 exit status
g++ -o boostTesting boostTesting.cpp -I /Users/myUsername/Downloads/boostCompiled/include/ -L /Users/myUsername/Downloads/boostCompiled/lib/ -l regex
ld: library not found for -lregex
collect2: ld returned 1 exit status
My shell is bash ... and I've set my DYLD_LIBRARY_PATH to the following:
export DYLD_LIBRARY_PATH=/usr/local/cuda/lib:/Users/myUsername/Downloads/boostCompiled/lib
It appears I'm not using the correct name to link (with the -l) option. Can somebody please help! Thanks in advance!
There shouldn't be a space between -L and /Users/myUsername/Downloads/boostCompiled/lib/
Make sure that libboost_regex.a is compiled in /Users/myUsername/Downloads/boostCompiled/lib.
Then this should work:
g++ -o boostTesting boostTesting.cpp -I/Users/myUsername/Downloads/boostCompiled/include/ -L/Users/myUsername/Downloads/boostCompiled/lib/ -lboost_regex