I'm new to programming c++ with g++ and have big problems to get wsdlpull-library to work. The version is 1.24.
I followed the installation steps from http://wsdlpull.sourceforge.net/.:
./configure --prefix=/home/jesse/Dropbox/Programmering/C++/test --disable-opt --enable-examples
make
make install
I then copied print.cpp file from the example to the "prefix"-directory. The next step would be "add the $(prefix)/include in your include path and add $(prefix)/libs and -lwsdl -lschema -lxmlpull to your LDFLAGS". The first problem is that there's no folder "libs" but "lib" and the include-folder has another folder inside named wsdlpull. Therefore I instead entered the following command:
g++ -I include/wsdlpull -L lib -lwsdl -lschema -lxmlpull -o print print.cpp
This resulted in the following error:
/usr/bin/ld: cannot find -lwsdl
/usr/bin/ld: cannot find -lschema
/usr/bin/ld: cannot find -lxmlpull
collect2: error: ld returned 1 exit status
I have no idea what this means, why does it look in /usr/bin/ld when I point to "lib"?
When you use -L lib, it means that, lib dir is available in pwd where you are doing make. Check whether you have said lib is really available or not.
To make things simple, you can give the absolute path of the lib folder.
i.e -L<path to lib>/lib. This would help the make to see the lib without any confusions.
Next, you might want to explicitly specify whether libwsdl is a static or shared library. Although this is optional.
Or, the best solution is to place the libraries in system libs location i.e /lib or /usr/lib or /use/local/lib and run ldconfig such that the linker/loader knows where the newly added libraries exists. In such case, you can simple issue -lwsdl without specifying the -L flag.
For more info, please refer ldconfig.
Related
The book Advanced Linux Programming contains:
The system searches only /lib and /usr/lib, by default. If a shared library that is linked into your program is installed outside those directories, it will not be found, and the system will refuse to run the program.
One solution to this problem is to use the -Wl, -rpath option when linking the program. Another solution to this problem is to set the LD_LIBRARY_PATH environment variable when running the program.
So from information above, I assume adding path to $LD_LIBRARY_PATH is equivalent to passing argument to linker when compiling something like -Wl,-rpath,SOME_PATH until I hit this problem:
I am trying to generate a shared library and this shared library depends on some .so files somewhere at my system. Here's the command for compilation:
g++ -fPIC -shared -Wl,-soname,libA.so -o libA.so SRC.cpp -L PATH_A -I PATH_B -Wl,-rpath,PATH_C:PATH_D:PATH_E -la -lb -lc
After I compile, I use ldd to check if there's any dependency issue and something unexpected to me happens:
Some of dependency are found and some of them are not (libA.so => not found), however all the paths it needs (PATH_C PATH_DPATH_E) have been passed to argument -Wl,-rpath.
So it seems -Wl,-rpath does not work for this case , the only solution to make it work is to add the path to libA.so to $LD_LIBRARY_PATH and ldd returns that all the dependency are found.
I would like to know why -Wl,-rpath fails in, what's the difference between adding the path to $LD_LIBRARY_PATH and passing an argument to -Wl,-rpath?
I am trying to build a shared library. My aim is to pull all dependencies as static libraries into a single shared library. My understanding is that this can be done with the -Wl,--whole-archiveflag. Here is a snippet of my CMake script responsible for configuring the shared library.
# shared library
add_library(semsim SHARED "${SEMSIM_HEADERS}" "${SEMSIM_SOURCES}") # created the shared library
#fPIC for linux shared library strs
set_property(TARGET semsim PROPERTY POSITION_INDEPENDENT_CODE ON) #turn fPIC on
target_compile_options(semsim PRIVATE -Wl,--whole-archive) # enable pulling static libraries into shared library
The error I'm getting whilst trying to compile (verbose mode is on) is:
/usr/bin/c++ -fPIC -std=c++14 -g -shared -Wl,-soname,libsemsim.so -o libsemsim.so CMakeFiles/semsim.dir/CurlGet.cpp.o CMakeFiles/semsim.dir/RDFNode.cpp.o CMakeFiles/semsim.dir/Subject.cpp.o CMakeFiles/semsim.dir/Predicate.cpp.o CMakeFiles/semsim.dir/Resource.cpp.o CMakeFiles/semsim.dir/Triple.cpp.o CMakeFiles/semsim.dir/SemsimUtils.cpp.o CMakeFiles/semsim.dir/MetaID.cpp.o CMakeFiles/semsim.dir/XmlAssistant.cpp.o CMakeFiles/semsim.dir/Reader.cpp.o CMakeFiles/semsim.dir/Editor.cpp.o CMakeFiles/semsim.dir/Writer.cpp.o CMakeFiles/semsim.dir/RDF.cpp.o CMakeFiles/semsim.dir/Participant.cpp.o CMakeFiles/semsim.dir/PhysicalEntity.cpp.o CMakeFiles/semsim.dir/PhysicalPhenomenon.cpp.o CMakeFiles/semsim.dir/PhysicalProcess.cpp.o CMakeFiles/semsim.dir/PhysicalPropertyResource.cpp.o CMakeFiles/semsim.dir/PhysicalForce.cpp.o CMakeFiles/semsim.dir/Query.cpp.o CMakeFiles/semsim.dir/SemsimCombineArchive.cpp.o CMakeFiles/semsim.dir/Triples.cpp.o ../../third_party/libCombine-0.2.3/INSTALL/lib/libcombine-static.a ../../third_party/zipper/INSTALL/lib/libZipper-static.a ../../third_party/zlib-1.2.11/INSTALL/lib/libz.a /usr/local/lib/libbz2.a /usr/local/lib/libxml2.a -ldl -lbz2 -lz -lcurl -lxslt
/usr/bin/ld: /usr/local/lib/libxml2.a(uri.o): relocation R_X86_64_PC32 against symbol `xmlFree' can not be used when making a shared object; recompile with -fPIC
/usr/bin/ld: final link failed: Bad value
collect2: error: ld returned 1 exit status
However, according to this question, /usr/local/lib/lxml2.a was already compiled fPIC:
(base) ciaran#DESKTOP:/usr/local/lib$ ls
cmake libcharset.so.1.0.0 libraptor2.a librasqal.la librdf.so libxml2.so.2
libbz2.a libcurlcpp.a libraptor2.la librasqal.so librdf.so.0 libxml2.so.2.9.10
libcharset.a libiconv.la libraptor2.so librasqal.so.3 librdf.so.0.0.0 pkgconfig
libcharset.la libiconv.so libraptor2.so.0 librasqal.so.3.0.0 libxml2.a python2.7
libcharset.so libiconv.so.2 libraptor2.so.0.0.0 librdf.a libxml2.la python3.6
libcharset.so.1 libiconv.so.2.6.1 librasqal.a librdf.la libxml2.so xml2Conf.sh
(base) ciaran#DESKTOP:/usr/local/lib$ readelf -d libxml2.a | grep TEXT
(base) ciaran#DESKTOP:/usr/local/lib$
This leads me to believe that perhaps I've misunderstood the error message - could somebody shed some light on what's going on here?
You haven't misunderstood the error message, or at least not significantly.
However, according to this question, /usr/local/lib/lxml2.a was already compiled fPIC
You conclude this because the command:
/usr/local/lib$ readelf -d libxml2.a | grep TEXT
outputs nothing, which shows that you chose the second most popular answer to
that question, although at this writing it is not nearly as up-voted as the most popular answer
I guess you did that because the most popular answer tells you how to test an object file for
PIC-ness, and you want to a test a library, as the second most popular answer does. Or
perhaps because you tried the most popular answer first and it indicated that your libxml2.a
was PIC.
But the second most popular answer tests a shared library, and you use it to test
the object files in a static library. A shared library is very different from
an object file, or a static library of such, and the question to which this answer was given asks how to test
the PIC-ness of an object file. So this answer does not answer the question: really
it suggests how to test whether a file that has a name like a shared library actually is
a shared library.
The most popular answer does answer the question, and if was a correct answer then
it would be the right one for you too, because what the linker has diagnosed:
/usr/local/lib/libxml2.a(uri.o): relocation R_X86_64_PC32 against symbol `xmlFree' \
can not be used when making a shared object; recompile with -fPIC
is that the object file uri.o archived in libxml2.a is not PIC.
But the most popular answer, notwithstanding its popularity, is invalid.
The PIC-ness test that it proposes - with no supporting argument - can
misidentify non-PIC object files as PIC (as perhaps you observed).
None of the answers to that question
is a correct answer for you, and it doesn't really matter why. The system linker itself
is the ultimate authority on whether an object file is or is not position-independent.
Any one-liner test other than attempting to link the object file into a DSO is just an attempt
to second-guess the linker: if its verdict differs from
the linker's it implies that the test is broken, not the linker.
And you already know the linker's verdict. It has tried to link libxml2.a(uri.o)
into a DSO and found that it can't, because the it contains a non-position-independent
relocation record.
The /usr/local/lib/libxml2.a you've got was built on the traditional
default assumption that the object files archived therein need not be compiled to
position-independent code (with -fPIC) because the static library would only
be input to the linkage of non-position-independent executables. If you want to
link some PI binary, then you'll link it with the shared libary libxml2.so,
which is PI by definition. Your libxml2.a was furthermore built with a compiler
that does not emit PI object code by default. It is possible that your current
compiler still has that increasingly antiquated trait, but you don't need to find
out.
You need to replace your local libxml2 install with one in which the object
files in libxml2 have been compiled with fPIC. If you already know how to do that you can skip the rest of this and get on with it.
If you have somewhere got the source package of libxml2 that was built
and installed and you want to stick with that revision, then cd into its root directory and run:
make uninstall
Otherwise, remove the installation by deleting, as root, all files and symlinks matching
/usr/local/lib/libxml2 and the directory /usr/local/include/libxml2
If you want to stick with a source package you've already got (where you ran make uninstall),
then, in its root directory, run:
make distclean
to restore to its pristine state.
If you don't have a source package you want to stick with, then clone or download-and-extract the latest from https://gitlab.gnome.org/GNOME/libxml2/,
then cd into the root directory and run:
./autogen.sh
to generate the build-system.
Whatever you've done thus far, in the package root directory then run:
./configure CFLAGS=-fPIC [any other non-default configuration options]
If that completes successfully, then run:
make
If that completes successfully, then as root run:
make install
If that completes successfully, then /usr/local/lib/libxml2.a will
be recreated containing PI object files and you will be able to link your
shared library against it.
If you are unsure about [any other non-default configuration options] for
the ./configure command, then run:
./configure -h
beforehand for help, and/or seek advice.
I am trying to compile and run a C++ program on a server where I don't have root access. I am having trouble linkingboost_iostreams library.
I can successfully compile my program by pointing to the boost installation directory using the -L flag as:
g++ -I path/to/boost/build/include -o out prog1.cpp prog2.cpp -L path/to/boost/build/lib -lboost_iostreams
However, if I run the program as ./out I get the error error while loading shared libraries: libboost_iostreams.so.1.67.0: cannot open shared object file: No such file or directory since the linker is not able to locate libboost_iostreams.so.1.67.0 (which DOES exist under path/to/boost/build/lib)
Thanks to this answer, I was able to explicitly specify LD_LIBRARY_PATH and run the program as
LD_LIBRARY_PATH="path/to/boost/build/lib" ./out.
Since I am not root, I can't run ldconfig either. I was wondering if there is a way to load dynamic libraries without having to prefix LD_LIBRARY_PATH when you run the program and no root access.
I have figured out a way to solve this using the method explained here https://amir.rachum.com/blog/2016/09/17/shared-libraries/. The solution is to use rpath during compilation.
According to the article The only difference between rpath and
runpath is the order they are searched in. Specifically, their
relation to LD_LIBRARY_PATH - rpath is searched in before
LD_LIBRARY_PATH while runpath is searched in after. The meaning of
this is that rpath cannot be changed dynamically with environment
variables while runpath can.
In short once you compile with -rpath path/to/boost/build/lib, the directory containing the library libboost_iostreams.so.1.67.0 is searched at runtime without having to prefix LD_LIBRARY_PATH="path/to/boost/build/lib" ./out.
After compiling with
g++ -I path/to/boost/build/include -o out prog1.cpp prog2.cpp -L path/to/boost/build/lib -lboost_iostreams -rpath path/to/boost/build/lib
I was able to run ./out without any issues.
EDIT 1
As pointed by Nikos in the comments, alternatively you can set your LD_LIBRARY_PATH by export LD_LIBRARY_PATH=path/to/boost/build/lib. Add this line to .~/.bashrc file so that it is not lost when you log out.
I have a very basic C++ project in code blocks that makes use of glfw.so and two other libraries that are compiled to .so files from another project, libHorde3D.so and libHorde3DUtils.so. The latter are placed in the project root folder, while glfw is somewhere in my /usr/lib (I think).
I have added the project folder to the linker and compiler search paths in code blocks. I have added the libHorde3D.so and libHorde3DUtils.so as well as glfw.so to the Link Libraries in the Linker Settings tab. I thought that this would be enough based on the previous similar questions here on stackoverflow.
However when I press build:
ld cannot find -lHorde3D.so
ld cannot find -lHorde3DUtils.so
ld cannot find -lglfw.so
My system is Arch Linux 64 and I am using GCC.
I also tried bopying libHorde3D.so and libHorde3DUtils.so in /usr/lib and /usr/lib64 with no success.
P.S. All search paths are copied across the Debug and Release target.
Say, if the library name is libmylibrary.so, then linker option to link against that library would look like -lmylibrary. Note that lib prefix and .so suffix are not there — they are added automatically by the linker. In your case it seems like you specified the wrong name. Try removing .so from it, that should solve the problem.
Here is a simple demonstration of how to trigger the failure by making a similar mistake:
$ echo 'int main() { return 0; }' > test.c
$ gcc -o test ./test.c -lc
$ gcc -o test ./test.c -lc.so
/usr/bin/ld: cannot find -lc.so
collect2: ld returned 1 exit status
$
The first command succeeds and the second one (with incorrect library name) fails.
You must not pass ".so". The linker options are
-lHorde3D -lHorde3DUtils -lglfw
This way the linker will search for "libHorde3D.so" etc. in the library path(s).
I am using festival TTS c++ API in my program.I have downloaded all files from http://www.cstr.ed.ac.uk/downloads/festival/2.0.95/
and install festival and speech_tools successfully on my UBUNTU 10.04
now when compile my c++ programme gcc gives error:
g++ -L/usr/lib -L/home/peeyush/Desktop/festival/src/lib -L/home/peeyush/Desktop/speech_tools/lib -o"peeyush" ./src/peeyush.o -llibeststring.a -llibestbase.a -llibestools.a -llibFestival.a
/usr/bin/ld: cannot find -llibeststring.a
collect2: ld returned 1 exit status
make: *** [peeyush] Error 1
so please help me to sort out this error.
-Thanks
Peeyush Chandel(INDIA)
When using the -l option, you don't specify the leading lib or trailing .a or .so parts of the name as they're assumed by the linker. You would want to use something like -leststring to pick it up (assuming that your -L path is set correctly.
Alternately you can specify the exact filename (so no -l, just libeststring.a) as part of the object list to link (make sure the order is right relative to your .o files), but I believe in that case you would have to specify the path as the linker won't know to search your -L path. Easiest is to use -l though.