Flags for g++ static link when using -nostartfiles -nodefaultlibs -nostdlib - gcc

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.

Related

How do I link libraries statically with gcc?

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.

Order of linkinkg libc and libpthread on FreeBSD

I have this simple c-code
It works fine when i link it as
gcc -g app.c.o -o app -lrt -lpthread -lc
But if we change order of linking libc and libthread
gcc -g app.c.o -o app -lrt -lc -lpthread
it does not work.
We know on FreeBSD stubs of pthread-functions in libc are made as weak reference.
For example
objdump -T /lib/libc.so.7 | grep pthread_cond_signal
00000000000e2bf0 w DF .text 0000000000000011 FBSD_1.0 pthread_cond_signal
It means order of linking is not matter. Why so?
Compile and link using the option -pthread. Note the missing "ell".
Update:
-pthread instructs all tools involved in creating a binary (pre-processor, compiler, linker) to take care that the application/library to be build runs as intended. (This obviously is only necessary if the source makes use of any member(s) of the pthread_*-family of functions.)
Whereas -lpthread links a library called libpthread, nothing more and nothing less.
The difference in detail is implementation specific.
Note: if -pthread has been specified -lpthread is not necessary as well as not recommended to be specfied.
The reason for the behavior is that the linker only does a single pass through the libraries in the provided order to resolve symbols.
So, it needs to know about the pthread_* functions from -lpthread before it can resolve references to those functions in later libraries.
I believe the use of weak references is so that you can have functions in -lc that need -lpthread, but if you don't reference those functions in -lc than it isn't an error that its references to pthread_* couldn't be resolved.

g++, static initialization and -nostdlib

Compiling / linking with -nostdlib seems to prevent static initialization, even if I add my own crti.s and crtn.s with .init/.fini sections.
Are there workarounds to make g++ generate static initialization code that is inserted in .init or that I can call manually?
This is what I tried:
g++ -o test.o -c -fno-use-cxa-atexit test.cc # has _start (entry point)
# that calls _init and _main
as -o crti.o crti.s # has _init in section .init
as -o crtn.o crtn.s
g++ -o test ./crti.o test.o -nodefaultlibs -nostartfiles ./crtn.o
-nodefaultlibs alone includes static initialization code and call, but forces use of libc-_start/_init.
-nodefaultlibs -nostartfiles allows me to use my own _start / _init, but does not include code or call to static initialization.
From gcc linker docs,
-nostdlib
Do not use the standard system startup files or libraries when
linking. No startup files and only the libraries you specify will be
passed to the linker, and options specifying linkage of the system
libraries, such as -static-libgcc or -shared-libgcc, are ignored.
Hence use,
-nodefaultlibs
Do not use the standard system libraries when linking. Only the libraries you specify will be passed to the linker, options specifying linkage of the system libraries, such as -static-libgcc or -shared-libgcc, will be ignored. The standard startup files are used normally, unless -nostartfiles is used. The compiler may generate calls to memcmp, memset, memcpy and memmove. These entries are usually resolved by entries in libc. These entry points should be supplied through some other mechanism when this option is specified.
Also try,
g++ -Wl, -static
-Wl passes the next command on to the linker
-static On systems that support dynamic linking, this prevents linking with
the shared libraries. On other systems, this option has no effect.

Compiling a dynamically linked library

I'm currently trying to compile a dynamically linked library (for a plugin system) using Windows and MinGW.
I compile each objects using this command line :
mingw-g++ -fPIC test.cpp
And the library using this line:
mingw-g++ -rdynamic -shared -Wl,-soname,test.so.1 -o test.so test.o
It doesn't work at all (using GCC with Linux, a similar line works though) : fPIC and rdynamic are ignored for some reason.
And while trying to make the library, it fails because the compiler try to link it with objects that are supposed to be resolved as I dynamically link it with the main binary.
So how do you compile this using MinGW?
Thanks :) !
-fPIC and -rdynamic are ignored because they are unused for Windows.
Also, .so is not the correct output extension for libraries on Windows.
To make a shared library for/on windows with GCC:
mingw-g++ -c file.cpp -o file.o
mingw-g++ -shared -Wl,--out-implib,libfile.a -o file.dll file.o
No more, no less.
And, documentation is always lovely to have: http://www.mingw.org/wiki/sampleDLL

how to link static library into dynamic library in gcc

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.

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