The correct way to use the GNU linker - c++

I am trying to use a couple of libraries, libglfw3-dev and libglew-dev, on an ubuntu environment but have been unable to get the linker to perform its intended purpose. I would normally use a makefile but for the purpose of debugging I have just used g++ on the CLI.
g++ -I-Iinclude -I/usr/include/GL -I/usr/include/GLFW -L/usr/lib/x86_64-linux-gnu/
I understand that I need to specify the libraries themselves with the -l flag but get an error of the form
/usr/bin/ld: cannot find -llibglfw
Here is some information about the locations of the packages (omitting irrelevancies)
root#Jake-Faptop:/usr/include/GLFW# dpkg -L libglfw3-dev
/usr/include/GLFW/glfw3.h
/usr/include/GLFW/glfw3native.h
/usr/lib/x86_64-linux-gnu/libglfw.so
root#Jake-Faptop:/usr/include/GLFW# dpkg -L libglew-dev
/usr/include/GL/glew.h
/usr/include/GL/glxew.h
/usr/include/GL/wglew.h
/usr/lib/x86_64-linux-gnu/libGLEW.so
The names of the shared libraries have been a matter of great confusion to me as it turns out they are named /usr/lib/x86_64-linux-gnu/libGLEW.so.2.1.0 and /usr/lib/x86_64-linux-gnu/libglfw.so.3.3
---EDIT---
In light of the advice given to omit prefixes and suffixes on the library names I am still getting linker errors on the following input
g++ -Iinclude -I/usr/include/GL -I/usr/include/GLFW -L/usr/lib/x86_64-linux-gnu/ -lGLEW -lglfw src/main.cpp -o build/main
->
/usr/bin/ld: main.cpp:(.text+0x3b): undefined reference to glfwTerminate'
/usr/bin/ld: main.cpp:(.text+0x54): undefined reference to `glfwWindowHint'
/usr/bin/ld: main.cpp:(.text+0x63): undefined reference to `glfwWindowHint'
/usr/bin/ld: main.cpp:(.text+0x72): undefined reference to glfwWindowHint'
Confused.com...

Remove lib at the beginning of the names. E.g. the library's name is
libGLEW.so.2.1.0
Link it with
-lGLEW
This will link to libxGLEW.so which usually is a symlink to a versioned library like libGLEW.so.2.1.0.
-llibrary
-l library
Search the library named library when linking. (The second alternative with the library as a separate argument is only for POSIX compliance and is not recommended.)
The -l option is passed directly to the linker by GCC. Refer to your linker documentation for exact details. The general description below applies to the GNU linker.
The linker searches a standard list of directories for the library. The directories searched include several standard system directories plus any that you specify with -L.
Static libraries are archives of object files, and have file names like liblibrary.a. Some targets also support shared libraries, which typically have names like liblibrary.so. If both static and shared libraries are found, the linker gives preference to linking with the shared library unless the -static option is used.
It makes a difference where in the command you write this option; the linker searches and processes libraries and object files in the order they are specified. Thus, ‘foo.o -lz bar.o’ searches library ‘z’ after file foo.o but before bar.o. If bar.o refers to functions in ‘z’, those functions may not be loaded.
https://gcc.gnu.org/onlinedocs/gcc/Link-Options.html

Related

Difference between -static -lxyz and -l:libxyz.a

Sory my english is bad.
I'm using visual code, my project is c++, -L./libs/curl/lib include only libcurl.a, that is static lib
When I build project with this link option, everything is ok:
LDFLAGS = -static -L./libs/curl/lib -lcurl -lssl -lcrypto -lsqlite3 -lpthread -ldl -lz
But when I use this link option:
LDFLAGS = -L./libs/curl/lib -l:libcurl.a -l:libssl.a -l:libcrypto.a -l:libsqlite3.a -l:libpthread.a -l:libdl.a -l:libz.a
I got this error:
/usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/libpthread.a(pthread_create.o): In function `allocate_stack':
/build/glibc-2ORdQG/glibc-2.27/nptl/allocatestack.c:526: undefined reference to `_dl_stack_flags'
/build/glibc-2ORdQG/glibc-2.27/nptl/allocatestack.c:652: undefined reference to `_dl_stack_flags'
/usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/libpthread.a(elision-lock.o): In function `do_set_elision_enable':
/build/glibc-2ORdQG/glibc-2.27/nptl/../sysdeps/unix/sysv/linux/x86/elision-conf.c:67: undefined reference to `_dl_x86_cpu_features'
/usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/libpthread.a(nptl-init.o): In function `__pthread_initialize_minimal_internal':
/build/glibc-2ORdQG/glibc-2.27/nptl/nptl-init.c:294: undefined reference to `_dl_cpuclock_offset'
/build/glibc-2ORdQG/glibc-2.27/nptl/nptl-init.c:429: undefined reference to `_dl_pagesize'
/build/glibc-2ORdQG/glibc-2.27/nptl/nptl-init.c:438: undefined reference to `_dl_pagesize'
/build/glibc-2ORdQG/glibc-2.27/nptl/nptl-init.c:454: undefined reference to `_dl_init_static_tls'
/build/glibc-2ORdQG/glibc-2.27/nptl/nptl-init.c:456: undefined reference to `_dl_wait_lookup_done'
/usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/libpthread.a(nptl-init.o): In function `__pthread_get_minstack':
/build/glibc-2ORdQG/glibc-2.27/nptl/nptl-init.c:475: undefined reference to `_dl_pagesize'
/usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/libdl.a(dlopen.o): In function `dlopen':
(.text+0x5): undefined reference to `__dlopen'
/usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/libdl.a(dlclose.o): In function `dlclose':
(.text+0x1): undefined reference to `__dlclose'
/usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/libdl.a(dlsym.o): In function `dlsym':
(.text+0x5): undefined reference to `__dlsym'
/usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/libdl.a(dlerror.o): In function `dlerror':
(.text+0x1): undefined reference to `__dlerror'
/usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/libdl.a(dladdr.o): In function `dladdr':
(.text+0x1): undefined reference to `__dladdr'
So my question is:
What difference between -static -lxyz and -l:libxyz.a link option?
does -static have implicit links to add other libs?
By default gcc or g++ will link against some standard libraries. The list of these libraries is architecture dependent, but you find libc libgcc and some others. To see the list of libraries used for the link you can add -v option. You will see the list of libraries passed to collect2. Since you are compiling for x86_64 the list will be probably (libc, libgcc and libgcc_s).
When you use the static option, you force the linker to use the static version of all the libraries, those you give with -l option and the default ones.
In the second case you give the linker the static version of your libraries, but for the other libraries it is the shared version that will be taken. If both static and shared libraries are found, the linker gives preference to linking with the shared library unless the -static option is used. from https://gcc.gnu.org/onlinedocs/gcc/Link-Options.html#Link-Options.
A last thing. The crt files are also different if you use static option. You can see it also with -v option.
In case you want to control exactly which library should be used there is the option nostdlib. when using this option, The compiler Do not use the standard system startup files or libraries when linking. No startup files and only the libraries you specify are passed to the linker, and options specifying linkage of the system libraries, such as -static-libgcc or -shared-libgcc, are ignored.

C++ - Problem Undefined Reference to PCM::getInstance()

Before i ask a new question, i have read few or more question about this, but i keep confuse.
I Compile my program with :
g++ -std=c++11 -Wall -O3 -fopenmp main.cpp -o main -D WITH_COUNTER -I /usr/local/src/pcm -L /usr/local/src/pcm -L /usr/local/lib
Then, i found the error :
main.cpp:(.text.startup+0x27e): undefined reference to PCM::getInstance()
main.cpp:(.text.startup+0x289): undefined reference to PCM::resetPMU()
main.cpp:(.text.startup+0x310): undefined reference to PCM::program(PCM::ProgramMode, void const*)
So, can anyone explain to me how to solve this?
You don't actually link with the libraries themselves.
The -L option tells the linker to add a directory to its search-path, but the linker will not go through all libraries in its path to find which might be correct (there could be hundreds or even thousands).
Instead you need to explicitly specify libraries to link with using the -l (lower-case L) option.
For some example library foo, there will exist a file named libfoo.a or libfoo.so. To link with it you use -lfoo.
If the documentation for your library doesn't tell you which library you should link with, look for a suitable named file (as mentioned above) and use the correct option to link with the library.

g++ not find .so files

I am trying to generate a c++ library using the g++ compiler. My library has another C library as dependency and I have compiled it in order to obtain the .so files.
I have the following structure:
src:
include/linux:
libcustom.a
libcustom.la
libcustom.so
libcustom.so.0
libcustom.so.0.0.0
Now, when I have all the .o files of my cpp classes, and I want to link the library, I execute the following command:
g++ -shared -L/usr/lib/R/lib -Wl,-Bsymbolic-functions -Wl,-z,relro -o mylibrary.so File1.o File2.o File3.o -L./include/linux -lc++ -lutil -lm -lcustom -Wl,-rpath='$ORIGIN/include/linux' -L/usr/lib/R/lib -lR
But it throws me the error:
libcustom.so.0: cannot open shared object file: No such file or directory
I am executing the command from the src directory.
I know it could be fixed editing the LD_LIBRARY_PATH, but the idea it is someone can use my library without the need of configuring anything, so I am trying to do that with the c++'s -rpath flag.
Any idea how can I fix it, or the reason for the error?
The error message you got seems to come from the run-time loader ld.so instead of the linker ld (I know the names are confusing). You have to distinguish between finding so's at link-time and at run-time. The -L flag you give at link-time has nothing to do with localizing the library at run-time.
Your rpath=./include/linux value is not correct, because dot is not recognized by the ld as relative path. Relative searching path should be given like
-Wl,-rpath='$ORIGIN/include/linux'
where the $ORIGIN represents the folder where your executable (not mylibrary.so) locates. Make sure to use single quote and not double quote because the string $ORIGIN should be passed to the linker literally and hard coded into the executable file.
More details goes
how to link to shared lib from shared lib with relative path
ld: Using -rpath,$ORIGIN inside a shared library (recursive)

Undefined symbol in static lib linked into dynamic library

here is my issue:
At runtime my program which load shared library fail to load one, it says:
libCommunicationModule.so: undefined symbol __builtin_delete
the context:
compiler: gcc 3.4
Linux Debian 4.0 (old stuff ....)
I have a static library: libtgi_cppd.a , I don't have the source of this library.
This lib is linked into the shared library libCommunicationModule.so with these options
-Wl,-whole-archive -ltgi_cppd
I enabled -y option on __builtin_delete to check:
libtgi_cppd.a(ClientAPI_cpp.o): reference to __builtin_delete
libtgi_cppd.a(ClientInterface.o): reference to __builtin_delete
libtgi_cppd.a(ClientAPI_cpp.o): reference to __builtin_delete
I try to add to link command -lstdc++ -lgcc before and after -whole-archive, no change.
$ nm libCommunicationModule.so | grep __builtin
result is always like this:
U __builtin_delete
U __builtin_new
U __builtin_vec_new
What can I do to solve this issue?
Thank you
Full command as requiered:
g++ -Wl,-y -Wl,__builtin_delete -Wl,--trace -Wl,-rpath,/usr/local/qt/lib -shared
-Wl,-soname,libCommunicationModule-x11-Debug.so.6 -Wl,-rpath,/home/sncf/AGC_IHM/AGC/Tms/Gui/Components/CommunicationModule/x11/Debug
-o libCommunicationModule-x11-Debug.so.6.0.1 x11/Debug/Obj/CommunicationModule-Build.o x11/Debug/Obj/CommunicationModuleFilesAutoGen.o x11/Debug/Obj/CommunicationModuleParamsAutoGen.o
x11/Debug/Obj/CommunicationModule.o
x11/Debug/Obj/CommunicationModuleAutoGen.o
x11/Debug/Obj/CommDebugDlg.o
x11/Debug/Obj/moc_CommunicationModule.o x11/Debug/Obj/moc_CommDebugDlg.o
-L/usr/local/qt/lib
-L/usr/X11R6/lib -lBuildInformations-x11-Debug
-lBagsLib-x11-Debug -lConfigParamsLib-x11-Debug
-lIniLib-x11-Debug -lModuleHandling-x11-Debug
-lGenericRuntimeInfoLib-x11-Debug
-lDebugLib-x11-Debug -lTCNLib-x11-Debug
-lGUITools-x11-Debug -lQtEventsLib-x11-Debug
-lPackUnpack-x11-Debug -L/home/sncf/AGC_IHM/AGC/Tms/Gui/ProjectLib/x11
-L/home/sncf/AGC_IHM/AGC/Tms/Gui/Components/AGCTCNClientAPI/2004.09.21/posix_linux_i586/lib
-lqt-mt -lXext -lX11 -lm -lpthread -Wl,-whole-archive -ltgi_cppd -lstdc++ -lgcc
You linked against a library which was compiled/linked by another compiler/linker version. What you need is to link against a library which was compiled and linked by the same compiler/linker as used by yourself, or you have to make sure, that the libraries are at least binary compatible.
Execute command ldd and it will list out all shared libraries using by your program.
Check the environment variable LIBPATH /LD_PATH in your execution environment. And make sure all those libraries are present in that path
Make sure all library files have sufficient permission

boost test - 'undefined reference' errors

I have two simple files:
runner.cpp:
#define BOOST_TEST_DYN_LINK
#define BOOST_TEST_MODULE Main
#include <boost/test/unit_test.hpp>
and test1.cpp:
#define BOOST_TEST_DYN_LINK
#ifdef STAND_ALONE
# define BOOST_TEST_MODULE Main
#endif
#include <boost/test/unit_test.hpp>
BOOST_AUTO_TEST_SUITE( Foo)
BOOST_AUTO_TEST_CASE( TestSomething )
{
BOOST_CHECK( true );
}
BOOST_AUTO_TEST_SUITE_END()
To compile, I'm using:
$ g++ -I/e/code/boost_1_52_0 -o runner -lboost_unit_test_framework runner.cpp test1.cpp
I get the following error:
C:\DOCUME~1\ADMINI~1\LOCALS~1\Temp\ccU0cDSz.o:runner.cpp:(.text+0x8c): multiple definition of `main'
c:/pdev/mingw/bin/../lib/gcc/i686-pc-mingw32/4.7.2/../../../libboost_unit_test_framework.a(unit_test_main.o):unit_test_main.cpp:(.text.startup+0x0): first defined here
c:/pdev/mingw/bin/../lib/gcc/i686-pc-mingw32/4.7.2/../../../libboost_unit_test_framework.a(unit_test_main.o):unit_test_main.cpp:(.text.startup+0x14): undefined reference to `init_unit_test_suite(int, char**)'
C:\DOCUME~1\ADMINI~1\LOCALS~1\Temp\ccU0cDSz.o:runner.cpp:(.text+0x52): undefined reference to `_imp___ZN5boost9unit_test9framework17master_test_suiteEv'
C:\DOCUME~1\ADMINI~1\LOCALS~1\Temp\ccU0cDSz.o:runner.cpp:(.text+0xb0): undefined reference to `_imp___ZN5boost9unit_test14unit_test_mainEPFbvEiPPc'
C:\DOCUME~1\ADMINI~1\LOCALS~1\Temp\ccU0cDSz.o:runner.cpp:(.text$_ZN5boost9unit_test13test_observerD2Ev[__ZN5boost9unit_test13test_observerD2Ev]+0xe): undefined reference to `_imp___ZTVN5boost9unit_test13test_observerE'
C:\DOCUME~1\ADMINI~1\LOCALS~1\Temp\ccU0cDSz.o:runner.cpp:(.text$_ZN5boost9unit_test13test_observerC2Ev[__ZN5boost9unit_test13test_observerC2Ev]+0xe): undefined reference to `_imp___ZTVN5boost9unit_test13test_observerE'
C:\DOCUME~1\ADMINI~1\LOCALS~1\Temp\ccU0cDSz.o:runner.cpp:(.text$_ZN5boost9unit_test15unit_test_log_tC1Ev[__ZN5boost9unit_test15unit_test_log_tC1Ev]+0x22): undefined reference to `_imp___ZTVN5boost9unit_test15unit_test_log_tE'
C:\DOCUME~1\ADMINI~1\LOCALS~1\Temp\cciSdkmB.o:test1.cpp:(.text+0x88): undefined reference to `_imp___ZN5boost9unit_test15unit_test_log_t14set_checkpointENS0_13basic_cstringIKcEEjS4_'
C:\DOCUME~1\ADMINI~1\LOCALS~1\Temp\cciSdkmB.o:test1.cpp:(.text+0x136): undefined reference to `_imp___ZN5boost10test_tools9tt_detail10check_implERKNS0_16predicate_resultERKNS_9unit_test12lazy_ostreamENS5_13basic_cstringIKcEEjNS1_10tool_levelENS1_10check_typeEjz'
C:\DOCUME~1\ADMINI~1\LOCALS~1\Temp\cciSdkmB.o:test1.cpp:(.text+0x21d): undefined reference to `_imp___ZN5boost9unit_test9ut_detail24auto_test_unit_registrarC1ENS0_13basic_cstringIKcEE'
C:\DOCUME~1\ADMINI~1\LOCALS~1\Temp\cciSdkmB.o:test1.cpp:(.text+0x284): undefined reference to `_imp___ZN5boost9unit_test9ut_detail24auto_test_unit_registrarC1EPNS0_9test_caseEm'
C:\DOCUME~1\ADMINI~1\LOCALS~1\Temp\cciSdkmB.o:test1.cpp:(.text+0x2a4): undefined reference to `_imp___ZN5boost9unit_test9ut_detail24auto_test_unit_registrarC1Ei'
C:\DOCUME~1\ADMINI~1\LOCALS~1\Temp\cciSdkmB.o:test1.cpp:(.text$_ZN5boost9unit_test14make_test_caseERKNS0_9callback0INS0_9ut_detail6unusedEEENS0_13basic_cstringIKcEE[__ZN5boost9unit_test14make_test_caseERKNS0_9callback0INS0_9ut_detail6unusedEEENS0_13basic_cstringIKcEE]+0x1d): undefined reference to `_imp___ZN5boost9unit_test9ut_detail24normalize_test_case_nameENS0_13basic_cstringIKcEE'
C:\DOCUME~1\ADMINI~1\LOCALS~1\Temp\cciSdkmB.o:test1.cpp:(.text$_ZN5boost9unit_test14make_test_caseERKNS0_9callback0INS0_9ut_detail6unusedEEENS0_13basic_cstringIKcEE[__ZN5boost9unit_test14make_test_caseERKNS0_9callback0INS0_9ut_detail6unusedEEENS0_13basic_cstringIKcEE]+0x5b): undefined reference to `_imp___ZN5boost9unit_test9test_caseC1ENS0_13basic_cstringIKcEERKNS0_9callback0INS0_9ut_detail6unusedEEE'
collect2.exe: error: ld returned 1 exit status
I'm using g++ 4.7.2 on MinGW, with boost 1.52.0.
I get the same errors when only trying to compile test1.cpp - except the "multiple main definition" one.
I perused the official documentation for quite a while, but its scarce on details regarding linking options. When I compiled the boost libs, besides unit_test_framework, I also got prg_exec_monitor and test_exec_monitor; perhaps I should link these somehow ? I tried many combinations, but all resulted in some kind of undefined reference linker error.
Complete list of boost generated libraries - I have them all in the project root:
libboost_prg_exec_monitor-mgw47-mt-1_52.a
libboost_prg_exec_monitor-mgw47-mt-1_52.dll
libboost_prg_exec_monitor-mgw47-mt-1_52.dll.a
libboost_prg_exec_monitor-mgw47-mt-d-1_52.a
libboost_prg_exec_monitor-mgw47-mt-d-1_52.dll
libboost_prg_exec_monitor-mgw47-mt-d-1_52.dll.a
libboost_test_exec_monitor-mgw47-mt-1_52.a
libboost_test_exec_monitor-mgw47-mt-d-1_52.a
libboost_unit_test_framework-mgw47-mt-1_52.a
libboost_unit_test_framework-mgw47-mt-1_52.dll
libboost_unit_test_framework-mgw47-mt-1_52.dll.a
libboost_unit_test_framework-mgw47-mt-d-1_52.a
libboost_unit_test_framework-mgw47-mt-d-1_52.dll
libboost_unit_test_framework-mgw47-mt-d-1_52.dll.a
With help from #llonesmiz, a number of issues were identified.
1. Libraries need to be specified after objects and sources which use them.
As described here:
The traditional behavior of linkers is to search for external functions from
left to right in the libraries specified on the command line. This means that a
library containing the definition of a function should appear after any source
files or object files which use it. This includes libraries specified with the
short-cut -l option, as shown in the following command:
$ gcc -Wall calc.c -lm -o calc (correct order)
With some linkers the opposite ordering (placing the -lm option before the file
which uses it) would result in an error,
$ cc -Wall -lm calc.c -o calc (incorrect order)
main.o: In function 'main':
main.o(.text+0xf): undefined reference to 'sqrt'
because there is no library or object file containing sqrt after ‘calc.c’. The
option -lm should appear after the file ‘calc.c’
2. Library paths should be explicitly specified.
If no lib paths are specified, the linker might look for the libs in a series
of default folders, thus loading a different library then intended. This is what
happened in my case - I wanted to link boost_unit_test_framework, but did not
specify a path because I assumed the linker would look in the current folder.
That's what happens at runtime, after all - if the dll is in the same folder
with the exe, it will find it.
I found it a little bit strange the linker would find the lib, since it was
named ibboost_unit_test_framework-mgw47-mt-1_52.dll. When I tried to link to
a non-existing lib, the linker complained though, so I assumed this isn't an
issue, and MinGW 's linker ignores those suffixes.
After some more research, I found this article about MinGW library paths.
The folders MinGW searches for libs can be found in the output of gcc -print-search-dirs.
The article also contains some bash magic to make sense of that output:
gcc -print-search-dirs | sed '/^lib/b 1;d;:1;s,/[^/.][^/]*/\.\./,/,;t 1;s,:[^=]*=,:;,;s,;,; ,g' | tr \; \\012 | grep -v '^ */'
This will print a nice list of those folders. gcc will not, by default,
look in the current directory for libs. I looked in each of them, and found the
lib that was being loaded - libboost_unit_test_framework.a, a static lib.
This brings into light another issue worth mentioning:
3. Static versus dynamic linking
I did not specify whether I want boost_unit_test_framework linked statically or dynamically.
In this case, gcc prefers dynamic linking:
Because of these advantages gcc compiles programs to use shared libraries by
default on most systems, if they are available. Whenever a static library
‘libNAME.a’ would be used for linking with the option -lNAME the compiler
first checks for an alternative shared library with the same name and a ‘.so’
extension.
(so is the extension for dynamic libraries on Unix - on Windows, the equivalent is dll.)
So, what happened is that gcc looked for libboost_unit_test_framework.dll
in all it's default folders, but couldn't find it. Then it looked for
libboost_unit_test_framework.a, and statically linked that. This resulted in
linking errors because the sources have #define BOOST_TEST_DYN_LINK, and
therefore expect to have the lib dynamically linked.
To enforce static or dynamic linking, the -Wl,-Bstatic and -Wl,-Bdynamic
linker options come into play, described here.
If I tell the linker that I want dynamic linking:
$ g++ -I/e/code/boost_1_52_0 runner.cpp test1.cpp -o runner -Wl,Bdynamic -lboost_unit_test_framework
This will fail, because the linker will not be able to find the dll.
4.Summary
The issues were:
libraries where specified before the sources which used them
the lib path wasn't specified
the type of linking wasn't specified
the name of the library was not correct
Final, working command:
$ g++ -I/e/code/boost_1_52_0 -o runner runner.cpp test1.cpp -L. -Wl,-Bdynamic -lboost_unit_test_framework-mgw47-mt-1_52