Under gcc (g++), I have compiled a static .a (call it some_static_lib.a) library. I want to link (is that the right phrase?) this .a file into another dynamic library (call it libsomeDyn.so) that I'm building. Though the .so compiles, I don't see content of .a under .so using nm command:
/usr/bin/g++ -fPIC -g -O2 -Wall -Werror -pipe -march=pentium3
-mtune=prescott -MD -D_FILE_OFFSET_BITS=64 -DLINUX -D_GNU_SOURCE -D_THREAD_SAFE -I../../../../../../../../ -I../../../../../../../..//libraries -Wl,-rpath,/usr/lib -o libsomeDyn.so some.o another.o some_static_lib.a -shared -Wl -x
-Wl,-soname,libsomeDyn.so
I do not see functions under some_static_lib.a under libsomeDyn.so. What am I doing wrong?
Static libraries have special rules when it comes to linking. An object from the static library will only be added to the binary if the object provides an unresolved symbol.
On Linux, you can change that behavior with the --whole-archive linker option:
g++ -Wl,--whole-archive some_static_lib.a -Wl,--no-whole-archive
For every one that comes across that problem like me (and has not understand the answer properly): here is a short howto generate a dynamic library (libmylib.so) from a static one (mylib.a):
1.) create a mylib.c file that only imports the mylib.h file
2.) compile this mylib.c to mylib.o with
gcc -c -fPIC mylib.c -o mylib.o
3.) generate a dynamic library with the following command:
gcc --whole-archive -shared -Wl,-soname,libmylib.so -o libmylib.so mylib.o mylib.a
That worked at least for me, turning a static library (compiled with -fPIC) to
a dynamic library. I'm not sure wether this will work for other libraries too.
Related
my makefile has these entries:
build_with_dynamic: main_executable_module.o decision.o data_io.o data_stat.o data_process.so
gcc -Wall -Wextra -Werror main_executable_module.o decision.o data_io.o data_stat.o -L. data_process.so -o ../../build/program
data_process.so: data_process_fPIC.o data_stat_fPIC.o
gcc -Wall -Wextra -Werror data_process_fPIC.o data_stat_fPIC.o -shared -o data_process.so
My makefile and my shared library are located in project/src/main_module, while my executable is located in project/build
I want to create an executable in the specified folder and link it to the shared library. Currently running the executable gives me this message:
dyld: Library not loaded: data_process.so
Referenced from: /Users/user/project/build/./program
Reason: image not found
I want to become able to run the program correctly without moving anything from their current positions and only via makefile commands. I have tried this, but nothing changed:
build_with_dynamic: main_executable_module.o decision.o data_io.o data_stat.o data_process.so
gcc -Wall -Wextra -Werror main_executable_module.o decision.o data_io.o data_stat.o -L. data_process.so -Wl,-rpath,. -o ../../build/program
The program works fine if i create the executable in the same folder as the library. How should i correctly write the makefile gcc line so that i can run the program? I run the make command from the same folder the makefile is located in.
I am trying to cross compile my application for a arm based system.
I have 2 libraries compiled in the following way:
$ gcc -shared --sysroot=$DIR_PATH -o $LIBPATH/libfoo.so foo.o
$ gcc -shared --sysroot=$DIR_PATH -o $LIBPATH/libbar.so bar.o
A third library is compiled:
gcc -shared -o $LIBPATH/libfoobar.so --sysroot=$DIR_PATH -L$LIBPATH -Wl,rpath=$RUN_TIME_PATH foobar.o -lfoo -lbar
Then finally I compile a binary:
gcc -o app --sysroot=$DIR_PATH -L$LIBPATH -Wl,rpath=$RUN_TIME_PATH app.o -lfoobar
However when compiling app I get
warning: libfoo.so, needed by libfoobar.so, not found (try using -rpath or -rpath-link)
I believe you need to use -Wl,-rpath-link=$LIBPATH to tell the linker where to look to resolve runtime library references during the link operation.
More info can be found in the ld documentation: https://sourceware.org/binutils/docs-2.37/ld/Options.html
I am new to C++ compiling/linking.
I am trying to link all libraries statically with gcc, I tried using LDFLAGS=-static but did not work. Error message showed:
/bin/sh ./libtool --tag=CXX --mode=link /home/dizhang/lib/hdf5/bin/h5c++ -g -O2 -L/home/dizhang/lib/blitz/lib -L/home/dizhang/lib/libconfig/lib -o angora src/libangora.la -lblitz -lconfig++
libtool: link: /home/dizhang/lib/hdf5/bin/h5c++ -g -O2 -o angora -L/home/dizhang/lib/blitz/lib -L/home/dizhang/lib/libconfig/lib src/.libs/libangora.a -L/bgsys/drivers/V1R2M2/ppc64/comm/lib64 -L/bgsys/drivers/V1R2M2/ppc64/comm/lib -L/bgsys/drivers/V1R2M2/ppc64/spi/lib -lpthread -lm /home/dizhang/lib/blitz/lib/libblitz.a /bgsys/drivers/V1R2M2/ppc64/comm/lib/libmpichcxx-gcc.so /bgsys/drivers/toolchain/V1R2M2_base/gnu-linux/powerpc64-bgq-linux/lib/libstdc++.so /bgsys/drivers/V1R2M2/ppc64/comm/lib/libmpich-gcc.so /bgsys/drivers/V1R2M2/ppc64/comm/lib/libopa-gcc.so /bgsys/drivers/V1R2M2/ppc64/comm/lib/libmpl-gcc.so /home/dizhang/lib/libconfig/lib/libconfig++.a /bgsys/drivers/toolchain/V1R2M2_base-efix014/gnu-linux/powerpc64-bgq-linux/lib/libstdc++.so -Wl,-rpath -Wl,/bgsys/drivers/toolchain/V1R2M2_base-efix014/gnu-linux/powerpc64-bgq-linux/lib -Wl,-rpath -Wl,/bgsys/drivers/V1R2M2/ppc64/comm/lib -Wl,-rpath -Wl,/bgsys/drivers/toolchain/V1R2M2_base/gnu-linux/powerpc64-bgq-linux/lib -Wl,-rpath -Wl,/bgsys/drivers/toolchain/V1R2M2_base-efix014/gnu-linux/powerpc64-bgq-linux/lib -Wl,-rpath -Wl,/bgsys/drivers/V1R2M2/ppc64/comm/lib -Wl,-rpath -Wl,/bgsys/drivers/toolchain/V1R2M2_base/gnu-linux/powerpc64-bgq-linux/lib
/bgsys/drivers/toolchain/V1R2M2_base-efix014/gnu-linux/lib/gcc/powerpc64-bgq-linux/4.4.7/../../../../powerpc64-bgq-linux/bin/ld: attempted static link of dynamic object `/bgsys/drivers/V1R2M2/ppc64/comm/lib/libmpichcxx-gcc.so'
collect2: ld returned 1 exit status
I did some search and found that, telling Makefile -Wl -Bstatic may solve this problem, but how exactly I should change this in my Makefile?
I tried searching -Wl in Makefile but it was not in the text.
Thanks,
Di
Looks like you are trying to build HDF5 with MPI support on BGQ.
As long as you end up passing a ".so" version of a lib to gcc on BGQ -- you will see this error. You may need to check how you are passing MPI info to HDF5's configure script.
In my case (building another project that uses CMake) passing BGQ's MPI compiler wrappers to CMake always created a problem where it would try to link MPI using the shared libs instead of the static ones. To resolve this, I had to make sure to explicitly specify the ".a" variants of the MPI libs.
Im developing an android app thats loading two shared libraries. One is external, its called libpcan.so . Usually its build to libpcan.so.0.6, this somehow cant be used by my android, i so changed the gcc flags compiling it from:
arm-linux-androideabi-gcc src/libpcan.c -fPIC -shared -O2 -Wall -Wl,-soname,-libpcan.so.0 -lc -I. -I../driver -DNO_RT -o -libpcan.so.0.6
ln -sf libpcan.so.0.6 libpcan.so
to
arm-linux-androideabi-gcc src/libpcan.c -fPIC -shared -O2 -Wall -lc -I. -I../driver -DNO_RT -o -libpcan.so
This .so has the same size as the so.0.6 so i assume it worked fine.
My own c-code is getting compiled with
arm-linux-androideabi -shared src/receivetest.c src/common.c -I. -I../lib -I../driver -L../lib -L/lib -L/usr/lib -L/usr/local/lib -o libreceivetest.so
I load both of these files, so the libpcan.so and the libreceivetest.so to my app
static {
System.loadLibrary("pcan");
System.loadLibrary("receivetest");
}
When I'm trying to launch that app i get the error message:
07-14 11:12:43.812: E/AndroidRuntime(753): java.lang.ExceptionInInitializerError
07-14 11:12:43.812: E/AndroidRuntime(753): Caused by: java.lang.UnsatisfiedLinkError: Cannot load library: reloc_library[1306]: 36 cannot locate 'CAN_Open'...
My receivetest is using that function, but since it declared in the libpcan.so and im also loading that library, i don't know where that error could come from.
I'd just guess its an error in my clags, since I'm new to building .so files via using gcc in the shell i don't really understand all the flags im using.
It's quite long since i solved this. But I haven't ever marked this question as solved.
Thanks to jww for reminding me.
As I've said in the comment to my question, the link to the function CAN_Open was missing due to a missing parameter at compiling the .so-file. The function CAN_Open is a part of the libpcan.so and by skipping the link to that file the CAN_Open function just never made it into the receivetest.so .
I've been trying to find the proper .a's and related flags for statically linking an app or SO under Linux. I know -static exists, but I can't use it as there's one specific SO I must link to.
To put it another way, I'm looking for the appropriate flags to statically link everything, except for a specific SO.
Thanks.
At my workplace we use -Bstatic and -Bdynamic but they are options to the linker ld. You can specify them with gcc using the -Wl option.
g++ -o app -Wl,-Bstatic -llib1 -llib2 -llib3 -Wl,-Bdynamic -llib4 app.o
Above shows command line for linking with lib1, lib2, and lib3 as static libraries and lib4 as a shared object library.