I'm writing a dynamic library that's loaded at runtime as a plugin. At runtime, the library fails to load with the following message:
dlerror:/path/to/so: undefined symbol: fstat
The dynamic library consists of a bunch of static libraries linked together, including libsodium. I've tracked down libsodium as the only place that fstat() is used in the library.
As I understand it, fstat() should be part of libc, and should not require additional libraries to be installed. What am I missing?
EDIT1:
I've found some additional information about how linking to fstat() is different than most functions, but I'm not sure exactly how it applies to my situation. I am compiling/linking libsodium with the provided makefiles for their distribution, and the dynamic library is being compiled with the compiler driver as recommended in that answer.
EDIT2: here's the linker command, generated by CMake:
/usr/bin/c++ -fPIC -O3 -DNDEBUG -rdynamic -nodefaultlibs -undefined_warning -fPIC -fvisibility=hidden -shared -Wl,-soname,lin.xpl -o src/xplane_plugin/lin.xpl src/path/to/object/file1.cpp.o src/path/to/object/file2.cpp.o src/plugin/libplugin.a /usr/local/lib/libpng16.a -lz src/plenty/of/dependencies.a lib/glew/libglew.a src/another/library.a /usr/local/lib/libsodium.a /usr/lib/x86_64-linux-gnu/libcurl.so lib/json11/libjson11.a -lpthread deps/some/library.a /usr/local/lib/libzip.a -lbz2 -llzma -lssl -lcrypto -lstdc++fs -lz
Related
I've installed ffmpeg using vcpkg install ffmpeg
When I include the dependency in my cmake project, like so:
find_path(AVCODEC_INCLUDE_DIR libavcodec/avcodec.h)
find_library(AVCODEC_LIBRARY avcodec)
find_path(AVFORMAT_INCLUDE_DIR libavformat/avformat.h)
find_library(AVFORMAT_LIBRARY avformat)
find_path(AVUTIL_INCLUDE_DIR libavutil/avutil.h)
find_library(AVUTIL_LIBRARY avutil)
find_path(AVDEVICE_INCLUDE_DIR libavdevice/avdevice.h)
find_library(AVDEVICE_LIBRARY avdevice)
target_link_libraries(${TARGET_NAME} PRIVATE
${AVCODEC_LIBRARY} ${AVFORMAT_LIBRARY} ${AVUTIL_LIBRARY} ${AVDEVICE_LIBRARY}
)
My windows build works fine, however, on linux, I get the error:
[29/29] Linking CXX shared library libjni.so
2021-11-14T12:38:02.510164800Z FAILED: libjni.so
2021-11-14T12:38:02.510171600Z : && /usr/bin/g++-11 -fPIC -O3 -DNDEBUG -shared -Wl,-soname,libjni.so -o libjni.so CMakeFiles/jni.dir/src/jni.cpp.o CMakeFiles/jni.dir/src/core/audio.cpp.o CMakeFiles/jni.dir/src/core/files.cpp.o CMakeFiles/jni.dir/src/core/fs/file_utils.cpp.o CMakeFiles/jni.dir/src/core/spectrogram.cpp.o CMakeFiles/jni.dir/src/core/utils.cpp.o -L/usr/lib/gcc/x86_64-linux-gnu/10 -Wl,-rpath,/root/build/Release/_deps/fmt-build /root/vcpkg/installed/x64-linux/lib/libfftw3f.a _deps/fmt-build/libfmt.so.8.0.1 _deps/xxhash-build/libxxhash.a /root/vcpkg/installed/x64-linux/lib/libavcodec.a /root/vcpkg/installed/x64-linux/lib/libavformat.a /root/vcpkg/installed/x64-linux/lib/libavutil.a /root/vcpkg/installed/x64-linux/lib/libavdevice.a _deps/kistream_proto_cpp-build/libgenerated_srcs.a -lm -Wl,--as-needed /root/vcpkg/installed/x64-linux/lib/libprotobuf.a -lpthread && :
2021-11-14T12:38:02.510185200Z /usr/bin/ld: /root/vcpkg/installed/x64-linux/lib/libavcodec.a(h264_intrapred_10bit.o): warning: relocation against `ff_pw_512' in read-only section `.text'
2021-11-14T12:38:02.510187600Z /usr/bin/ld: /root/vcpkg/installed/x64-linux/lib/libavcodec.a(vc1dsp_mmx.o): relocation R_X86_64_PC32 against symbol `ff_pw_9' can not be used when making a shared object; recompile with -fPIC
I think, your issue is related to Position Independent Code. It can be resolved if you compile by giving -fPIC option in vcpkg.
You can look at this github issue of vcpkg repo. They gave an example that how can add compiler option to vcpkg`s port CMake file.
So i am trying to compile a simple GLFW window app, and i ran into a linker problem.
gcc -o bin/mtx_gui `pkg-config --libs glfw3 glew` src/main.c
i use this command to compile single main. pkg-config expands into -L/usr/local/lib -lglfw3 -lGLEW -lGLU -lGL which should compile everything. i checked all libs are where they suposed to be. no idea why it is not linking it
main.c:(.text.startup+0x2): undefined reference to `glfwInit'
First, as pointed by G.M in the comment, main.c goes before all libs. second and the most important.
-lglfw3 -lrt -lm -ldl -lpthread -lGL
Libpthread must be also linked, and if you plan on using opengl link Libgl as shown above.
I want to check whether a shared library was compiled with the -fPIC flag. What are the possible ways (on Linux, x86_64) to check this?
Is -fPIC implied (thus making the check redundant?)
Yes, GCC wouldn't allow you to link shared library without -fPIC so you don't need to check anything:
$ gcc tmp.c -shared
/usr/bin/ld: /tmp/ccqQVR9Y.o: relocation R_X86_64_32 against `compare' can not be used when making a shared object; recompile with -fPIC
/tmp/ccqQVR9Y.o: error adding symbols: Bad value
collect2: error: ld returned 1 exit status
$ gcc tmp.c -shared -fPIC
EDIT
Technically speaking you can compile shared library without -fPIC if none of it's functions calls other functions or accesses global variables. But in that case generated code would be the same as with -fPIC.
Some architectures (not necessarily "modern" ones) just don't have absolute addressing modes, all code is position independent there.
I am developing an application in Linux, which requires static library of curl.Only http and https support is required.I have tried many ways like -Wl,-Bstatic -libcurl , linking to libcurl.a etc. Most alarming is that, I haven't seen anybody who has been successful in doing so, in linux.Only thing I found was in Windows,
Linking project with statically build curl
But in linux , almost all answers are like following.
Static linking libcurl using c.
Is it so? Whether it is impossible to make standalone library of curl in linux ?
Following are my build options and results
-Wl,-Bstatic -pthread -lcrypto -Wl,-Bdynamic -ldl -lcurl
No error !!!!!
-Wl,-Bstatic -pthread -lcrypto -ldl -lcurl
errors ... cannot find -lgcc_s
-static -pthread -lcrypto -ldl -lcurl
lot of errors starting with undefined reference "idn_free"
4.-static -pthread -lcrypto -ldl -ldn -lcurl
no change.... lot of errors starting with undefined reference "idn_free"
-static /usr/lib/i386-linux-gnu/libpthread.a /usr/lib/i386-linux-gnu/libcrypto.a /usr/lib/i386-linux-gnu/libdl.a /usr/lib/i386-linux-gnu/libidn.a /usr/lib/i386-linux-gnu/libcurl.a
no change.... lot of errors starting with undefined reference "idn_free"
I'm trying to install GHC with -fPIC support in Fedora.
I've grabbed a source tarball since it seems no binary one has this.
In Build.mk i've changed the quick build type to
ifeq "$(BuildFlavour)" "quick"
SRC_HC_OPTS = -H64m -O0 -fasm -fPIC
GhcStage1HcOpts = -O -fasm -fPIC
GhcStage2HcOpts = -O0 -fasm -fPIC
GhcLibHcOpts = -O -fasm -fPIC
SplitObjs = NO
HADDOCK_DOCS = NO
BUILD_DOCBOOK_HTML = NO
BUILD_DOCBOOK_PS = NO
BUILD_DOCBOOK_PDF = NO
endif
unfortunately, when compiling i still get the ld error
ghc -fglasgow-exts --make -shared -oHs2lib.a /tmp/Hs2lib924498/Hs2lib.hs dllmain.o -static -fno-warn-deprecated-flags -O2 -package ghc -package Hs2lib -i/home/phyx/Documents/Haskell/Hs2lib -optl-Wl,-s -funfolding-use-threshold=16 -optc-O3 -optc-ffast-math
Linking a.out ...
/usr/bin/ld: /tmp/Hs2lib924498/Hs2lib.o: relocation R_X86_64_32 against `ghczmprim_GHCziUnit_Z0T_closure' can not be used when making a shared object; recompile with -fPIC
/tmp/Hs2lib924498/Hs2lib.o: could not read symbols: Bad value
So it seems that GHC-prim still isn't compiled with -FPIC
I've also told cabal to build any packages with -fPIC and shared.
Anyone have any ideas?
EDIT:
Thanks to dcouts I've been able to make some progress. But now i'm at the point where I thnk libffi isn't compiled with -fPIC. I've edited the makefile(.in) for it but so far, no luck.
The new command is:
ghc -fPIC -shared dllmain.o Hs2lib.o /usr/local/lib/ghc-7.0.3/libHSrts.a -o Hs2lib.so
where dllmain.c and Hs2lib.hs have both been compiled using -fPIC.
The error I get is:
/usr/bin/ld: /usr/local/lib/ghc-7.0.3/libHSffi.a(closures.o): relocation R_X86_64_32
against `.rodata' can not be used when making a shared object; recompile with -fPIC
/usr/local/lib/ghc-7.0.3/libHSffi.a: could not read symbols: Bad value
collect2: ld returned 1 exit status
After you see this error, do the following:
cd /tmp/Hs2lib924498/
ghc -fglasgow-exts --make -shared -oHs2lib.a /tmp/Hs2lib924498/Hs2lib.hs dllmain.o -static -fno-warn-deprecated-flags -fPIC -O2 -package ghc -package Hs2lib -i/home/phyx/Documents/Haskell/Hs2lib -optl-Wl,-s -funfolding-use-threshold=16 -optc-O3 -optc-ffast-math
Note I added -fPIC to the failed ghc command.
Once the command succeeds, continue the compilation from within the tmp directory without cleaning already compiled files. It should skip them and continue where it ended.
There's an FAQ entry on this topic on the Haskell Stack page.
It basically says the problem is environment related and sometimes non-deterministic.
The issue may be related to the use of hardening flags in some cases, specifically those related to producing position independent executables (PIE).
There's also a work around suggestion for Arch Linux:
On Arch Linux, installing the ncurses5-compat-libs package from AUR resolves this issue.