https://stackoverflow.com/questions/22601051
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RussianCould you be facing an
extern "C"
problem?
gcc undefined reference even though ld finds the library and it contains the desired function
题
I work on a number of projects for which I must cross compile a number of libraries, some internal, some not. When working on a cross compiled application for one of our systems, I had to import some cross compiled internal libraries for my application. I'm using autotools for the application within Eclipse. The problem happens regardless of whether I'm in Eclipse or not. It happens regardless of platform for which I'm compiling, so all of my various versions of gcc encounter the same linking error. When I compile the application, the individual modules (*.c) compile fine, but when the final gcc command is issued to link everything into the final program, I get an 'undefined reference to GetCanMpdConfig' error.
Now, here's the kicker: the linker actually finds the file (I've verified this with -Wl,--verbose to get gcc to print the linker script). I direct your attention specifically to the line regarding -lcanmpdconf :
Making clean in src
make[1]: Entering directory `/home/amarshall3/workspace/can_mpd/src'
test -z "can_mpd" || rm -f can_mpd
rm -f *.o
make[1]: Leaving directory `/home/amarshall3/workspace/can_mpd/src'
make[1]: Entering directory `/home/amarshall3/workspace/can_mpd'
make[1]: Nothing to be done for `clean-am'.
make[1]: Leaving directory `/home/amarshall3/workspace/can_mpd'
Making all in src
make[1]: Entering directory `/home/amarshall3/workspace/can_mpd/src'
i686-linux-gnu-g++ -DPACKAGE_NAME=\"can_mpd\" -DPACKAGE_TARNAME=\"can_mpd\" -DPACKAGE_VERSION=\"1.13\" -DPACKAGE_STRING=\"can_mpd\ 1.13\" -DPACKAGE_BUGREPORT=\"\" -DPACKAGE_URL=\"\" -DPLATFORM=generic_x86 -I. -DBUILDSTAMP="\"`date '+%F %T'`\"" -I../dependencies/canmpdconf/1.0/generic_x86/include -I../dependencies/mow2monitor/1.0/generic_x86/include -DGENERIC_X86 -g -ggdb -O0 -Wall -Wl,--verbose -MT can_mpd-can_mpd.o -MD -MP -MF .deps/can_mpd-can_mpd.Tpo -c -o can_mpd-can_mpd.o `test -f 'can_mpd.cpp' || echo './'`can_mpd.cpp
mv -f .deps/can_mpd-can_mpd.Tpo .deps/can_mpd-can_mpd.Po
i686-linux-gnu-g++ -DPACKAGE_NAME=\"can_mpd\" -DPACKAGE_TARNAME=\"can_mpd\" -DPACKAGE_VERSION=\"1.13\" -DPACKAGE_STRING=\"can_mpd\ 1.13\" -DPACKAGE_BUGREPORT=\"\" -DPACKAGE_URL=\"\" -DPLATFORM=generic_x86 -I. -DBUILDSTAMP="\"`date '+%F %T'`\"" -I../dependencies/canmpdconf/1.0/generic_x86/include -I../dependencies/mow2monitor/1.0/generic_x86/include -DGENERIC_X86 -g -ggdb -O0 -Wall -Wl,--verbose -MT can_mpd-mpd_can.o -MD -MP -MF .deps/can_mpd-mpd_can.Tpo -c -o can_mpd-mpd_can.o `test -f 'mpd_can.cpp' || echo './'`mpd_can.cpp
mv -f .deps/can_mpd-mpd_can.Tpo .deps/can_mpd-mpd_can.Po
i686-linux-gnu-g++ -DPACKAGE_NAME=\"can_mpd\" -DPACKAGE_TARNAME=\"can_mpd\" -DPACKAGE_VERSION=\"1.13\" -DPACKAGE_STRING=\"can_mpd\ 1.13\" -DPACKAGE_BUGREPORT=\"\" -DPACKAGE_URL=\"\" -DPLATFORM=generic_x86 -I. -DBUILDSTAMP="\"`date '+%F %T'`\"" -I../dependencies/canmpdconf/1.0/generic_x86/include -I../dependencies/mow2monitor/1.0/generic_x86/include -DGENERIC_X86 -g -ggdb -O0 -Wall -Wl,--verbose -MT can_mpd-mpd_multiplexing.o -MD -MP -MF .deps/can_mpd-mpd_multiplexing.Tpo -c -o can_mpd-mpd_multiplexing.o `test -f 'mpd_multiplexing.cpp' || echo './'`mpd_multiplexing.cpp
mv -f .deps/can_mpd-mpd_multiplexing.Tpo .deps/can_mpd-mpd_multiplexing.Po
i686-linux-gnu-g++ -DPACKAGE_NAME=\"can_mpd\" -DPACKAGE_TARNAME=\"can_mpd\" -DPACKAGE_VERSION=\"1.13\" -DPACKAGE_STRING=\"can_mpd\ 1.13\" -DPACKAGE_BUGREPORT=\"\" -DPACKAGE_URL=\"\" -DPLATFORM=generic_x86 -I. -DBUILDSTAMP="\"`date '+%F %T'`\"" -I../dependencies/canmpdconf/1.0/generic_x86/include -I../dependencies/mow2monitor/1.0/generic_x86/include -DGENERIC_X86 -g -ggdb -O0 -Wall -Wl,--verbose -MT can_mpd-serial_can_provider.o -MD -MP -MF .deps/can_mpd-serial_can_provider.Tpo -c -o can_mpd-serial_can_provider.o `test -f 'provider/serial_can_provider.cpp' || echo './'`provider/serial_can_provider.cpp
mv -f .deps/can_mpd-serial_can_provider.Tpo .deps/can_mpd-serial_can_provider.Po
i686-linux-gnu-g++ -DPACKAGE_NAME=\"can_mpd\" -DPACKAGE_TARNAME=\"can_mpd\" -DPACKAGE_VERSION=\"1.13\" -DPACKAGE_STRING=\"can_mpd\ 1.13\" -DPACKAGE_BUGREPORT=\"\" -DPACKAGE_URL=\"\" -DPLATFORM=generic_x86 -I. -DBUILDSTAMP="\"`date '+%F %T'`\"" -I../dependencies/canmpdconf/1.0/generic_x86/include -I../dependencies/mow2monitor/1.0/generic_x86/include -DGENERIC_X86 -g -ggdb -O0 -Wall -Wl,--verbose -MT can_mpd-komodo_can_provider.o -MD -MP -MF .deps/can_mpd-komodo_can_provider.Tpo -c -o can_mpd-komodo_can_provider.o `test -f 'provider/komodo_can_provider.cpp' || echo './'`provider/komodo_can_provider.cpp
mv -f .deps/can_mpd-komodo_can_provider.Tpo .deps/can_mpd-komodo_can_provider.Po
i686-linux-gnu-gcc -DPACKAGE_NAME=\"can_mpd\" -DPACKAGE_TARNAME=\"can_mpd\" -DPACKAGE_VERSION=\"1.13\" -DPACKAGE_STRING=\"can_mpd\ 1.13\" -DPACKAGE_BUGREPORT=\"\" -DPACKAGE_URL=\"\" -DPLATFORM=generic_x86 -I. -g -O2 -MT komodo.o -MD -MP -MF .deps/komodo.Tpo -c -o komodo.o `test -f 'can/komodo/komodo.c' || echo './'`can/komodo/komodo.c
mv -f .deps/komodo.Tpo .deps/komodo.Po
i686-linux-gnu-g++ -DBUILDSTAMP="\"`date '+%F %T'`\"" -I../dependencies/canmpdconf/1.0/generic_x86/include -I../dependencies/mow2monitor/1.0/generic_x86/include -DGENERIC_X86 -g -ggdb -O0 -Wall -Wl,--verbose -L../dependencies/canmpdconf/1.0/generic_x86/lib -L../dependencies/mow2monitor/1.0/generic_x86/lib -Wl,--verbose -o can_mpd can_mpd-can_mpd.o can_mpd-mpd_can.o can_mpd-mpd_multiplexing.o can_mpd-serial_can_provider.o can_mpd-komodo_can_provider.o komodo.o -lcanmpdconf -lmow2monitor -lpthread -ldl
GNU ld (GNU Binutils for Ubuntu) 2.23.52.20130913
Supported emulations:
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elf32_x86_64
elf_x86_64
elf_l1om
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GNU ld (GNU Binutils for Ubuntu) 2.23.52.20130913
Supported emulations:
elf_i386
i386linux
elf32_x86_64
elf_x86_64
elf_l1om
elf_k1om
i386pep
i386pe
using internal linker script:
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==================================================
attempt to open /usr/lib/gcc/i686-linux-gnu/4.8/../../../i386-linux-gnu/crt1.o succeeded
/usr/lib/gcc/i686-linux-gnu/4.8/../../../i386-linux-gnu/crt1.o
attempt to open /usr/lib/gcc/i686-linux-gnu/4.8/../../../i386-linux-gnu/crti.o succeeded
/usr/lib/gcc/i686-linux-gnu/4.8/../../../i386-linux-gnu/crti.o
attempt to open /usr/lib/gcc/i686-linux-gnu/4.8/crtbegin.o succeeded
/usr/lib/gcc/i686-linux-gnu/4.8/crtbegin.o
attempt to open can_mpd-can_mpd.o succeeded
can_mpd-can_mpd.o
attempt to open can_mpd-mpd_can.o succeeded
can_mpd-mpd_can.o
attempt to open can_mpd-mpd_multiplexing.o succeeded
can_mpd-mpd_multiplexing.o
attempt to open can_mpd-serial_can_provider.o succeeded
can_mpd-serial_can_provider.o
attempt to open can_mpd-komodo_can_provider.o succeeded
can_mpd-komodo_can_provider.o
attempt to open komodo.o succeeded
komodo.o
attempt to open ../dependencies/canmpdconf/1.0/generic_x86/lib/libcanmpdconf.so succeeded
-lcanmpdconf (../dependencies/canmpdconf/1.0/generic_x86/lib/libcanmpdconf.so)
attempt to open ../dependencies/canmpdconf/1.0/generic_x86/lib/libmow2monitor.so failed
attempt to open ../dependencies/canmpdconf/1.0/generic_x86/lib/libmow2monitor.a failed
attempt to open ../dependencies/mow2monitor/1.0/generic_x86/lib/libmow2monitor.so succeeded
-lmow2monitor (../dependencies/mow2monitor/1.0/generic_x86/lib/libmow2monitor.so)
attempt to open ../dependencies/canmpdconf/1.0/generic_x86/lib/libpthread.so failed
attempt to open ../dependencies/canmpdconf/1.0/generic_x86/lib/libpthread.a failed
attempt to open ../dependencies/mow2monitor/1.0/generic_x86/lib/libpthread.so failed
attempt to open ../dependencies/mow2monitor/1.0/generic_x86/lib/libpthread.a failed
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attempt to open /usr/lib/gcc/i686-linux-gnu/4.8/../../../i386-linux-gnu/libpthread.so succeeded
opened script file /usr/lib/gcc/i686-linux-gnu/4.8/../../../i386-linux-gnu/libpthread.so
opened script file /usr/lib/gcc/i686-linux-gnu/4.8/../../../i386-linux-gnu/libpthread.so
attempt to open /lib/i386-linux-gnu/libpthread.so.0 succeeded
/lib/i386-linux-gnu/libpthread.so.0
attempt to open /usr/lib/i386-linux-gnu/libpthread_nonshared.a succeeded
attempt to open ../dependencies/canmpdconf/1.0/generic_x86/lib/libdl.so failed
attempt to open ../dependencies/canmpdconf/1.0/generic_x86/lib/libdl.a failed
attempt to open ../dependencies/mow2monitor/1.0/generic_x86/lib/libdl.so failed
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attempt to open /usr/lib/gcc/i686-linux-gnu/4.8/libdl.so failed
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attempt to open /usr/lib/gcc/i686-linux-gnu/4.8/../../../i386-linux-gnu/libdl.so succeeded
-ldl (/usr/lib/gcc/i686-linux-gnu/4.8/../../../i386-linux-gnu/libdl.so)
attempt to open ../dependencies/canmpdconf/1.0/generic_x86/lib/libstdc++.so failed
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attempt to open /usr/lib/gcc/i686-linux-gnu/4.8/libstdc++.so succeeded
-lstdc++ (/usr/lib/gcc/i686-linux-gnu/4.8/libstdc++.so)
attempt to open ../dependencies/canmpdconf/1.0/generic_x86/lib/libm.so failed
attempt to open ../dependencies/canmpdconf/1.0/generic_x86/lib/libm.a failed
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attempt to open /usr/lib/gcc/i686-linux-gnu/4.8/../../../i386-linux-gnu/libm.so succeeded
-lm (/usr/lib/gcc/i686-linux-gnu/4.8/../../../i386-linux-gnu/libm.so)
attempt to open ../dependencies/canmpdconf/1.0/generic_x86/lib/libgcc_s.so failed
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attempt to open ../dependencies/mow2monitor/1.0/generic_x86/lib/libgcc_s.a failed
attempt to open /usr/lib/gcc/i686-linux-gnu/4.8/libgcc_s.so succeeded
-lgcc_s (/usr/lib/gcc/i686-linux-gnu/4.8/libgcc_s.so)
attempt to open ../dependencies/canmpdconf/1.0/generic_x86/lib/libgcc.so failed
attempt to open ../dependencies/canmpdconf/1.0/generic_x86/lib/libgcc.a failed
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attempt to open /usr/lib/gcc/i686-linux-gnu/4.8/libgcc.a succeeded
attempt to open ../dependencies/canmpdconf/1.0/generic_x86/lib/libc.so failed
attempt to open ../dependencies/canmpdconf/1.0/generic_x86/lib/libc.a failed
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attempt to open ../dependencies/mow2monitor/1.0/generic_x86/lib/libc.a failed
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attempt to open /usr/lib/gcc/i686-linux-gnu/4.8/libc.a failed
attempt to open /usr/lib/gcc/i686-linux-gnu/4.8/../../../i386-linux-gnu/libc.so succeeded
opened script file /usr/lib/gcc/i686-linux-gnu/4.8/../../../i386-linux-gnu/libc.so
opened script file /usr/lib/gcc/i686-linux-gnu/4.8/../../../i386-linux-gnu/libc.so
attempt to open /lib/i386-linux-gnu/libc.so.6 succeeded
/lib/i386-linux-gnu/libc.so.6
attempt to open /usr/lib/i386-linux-gnu/libc_nonshared.a succeeded
(/usr/lib/i386-linux-gnu/libc_nonshared.a)elf-init.oS
(/usr/lib/i386-linux-gnu/libc_nonshared.a)atexit.oS
attempt to open /lib/i386-linux-gnu/ld-linux.so.2 succeeded
/lib/i386-linux-gnu/ld-linux.so.2
attempt to open ../dependencies/canmpdconf/1.0/generic_x86/lib/libgcc_s.so failed
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attempt to open ../dependencies/mow2monitor/1.0/generic_x86/lib/libgcc_s.so failed
attempt to open ../dependencies/mow2monitor/1.0/generic_x86/lib/libgcc_s.a failed
attempt to open /usr/lib/gcc/i686-linux-gnu/4.8/libgcc_s.so succeeded
-lgcc_s (/usr/lib/gcc/i686-linux-gnu/4.8/libgcc_s.so)
attempt to open ../dependencies/canmpdconf/1.0/generic_x86/lib/libgcc.so failed
attempt to open ../dependencies/canmpdconf/1.0/generic_x86/lib/libgcc.a failed
attempt to open ../dependencies/mow2monitor/1.0/generic_x86/lib/libgcc.so failed
attempt to open ../dependencies/mow2monitor/1.0/generic_x86/lib/libgcc.a failed
attempt to open /usr/lib/gcc/i686-linux-gnu/4.8/libgcc.so failed
attempt to open /usr/lib/gcc/i686-linux-gnu/4.8/libgcc.a succeeded
attempt to open /usr/lib/gcc/i686-linux-gnu/4.8/crtend.o succeeded
/usr/lib/gcc/i686-linux-gnu/4.8/crtend.o
attempt to open /usr/lib/gcc/i686-linux-gnu/4.8/../../../i386-linux-gnu/crtn.o succeeded
/usr/lib/gcc/i686-linux-gnu/4.8/../../../i386-linux-gnu/crtn.o
ld-linux.so.2 needed by /lib/i386-linux-gnu/libpthread.so.0
found ld-linux.so.2 at /lib/i386-linux-gnu/ld-linux.so.2
libm.so.6 needed by /usr/lib/gcc/i686-linux-gnu/4.8/libstdc++.so
found libm.so at /usr/lib/gcc/i686-linux-gnu/4.8/../../../i386-linux-gnu/libm.so
make[1]: Leaving directory `/home/amarshall3/workspace/can_mpd/src'
can_mpd-can_mpd.o: In function `main':
/home/amarshall3/workspace/can_mpd/src/can_mpd.cpp:180: undefined reference to `GetCanMpdConfig(CAN_MPD_CONFIG*, unsigned int*)'
collect2: error: ld returned 1 exit status
make[1]: *** [can_mpd] Error 1
make: *** [all-recursive] Error 1
I have also verified that the library is for the correct platform (x86) and so therefore is in the correct format. I've also verified that it does indeed contain the required symbol (GetCanMpdConfig) with the output of nm:
0000305c B __bss_start
0000305c b completed.6608
w __cxa_finalize@@GLIBC_2.1.3
00000940 t deregister_tm_clones
000009d0 t __do_global_dtors_aux
00002e88 t __do_global_dtors_aux_fini_array_entry
00003058 d __dso_handle
00002ee4 d _DYNAMIC
0000305c D _edata
00003060 B _end
U __errno_location@@GLIBC_2.0
00002ea0 d Errors
U fclose@@GLIBC_2.1
U fgets@@GLIBC_2.0
00001184 T _fini
U fopen@@GLIBC_2.1
U __fprintf_chk@@GLIBC_2.3.4
00000a20 t frame_dummy
00002e84 t __frame_dummy_init_array_entry
000014e8 r __FRAME_END__
00000ef0 T GetCanMpdConfError
00000b60 T GetCanMpdConfig
00000a60 T GetCanMpdConfVersion
U GetConfigFilePath
00003000 d _GLOBAL_OFFSET_TABLE_
w __gmon_start__
00002ec0 d Handlers
000007c4 T _init
w _ITM_deregisterTMCloneTable
w _ITM_registerTMCloneTable
00002e8c d __JCR_END__
00002e8c d __JCR_LIST__
w _Jv_RegisterClasses
00000f20 T read_provider_type
000010c0 T read_serial_baud
00001010 T read_serial_device
00000980 t register_tm_clones
00000a80 T SetCanMpdConfig
U __stack_chk_fail@@GLIBC_2.4
00001170 t __stack_chk_fail_local
U strchr@@GLIBC_2.0
U strlen@@GLIBC_2.0
U strncmp@@GLIBC_2.0
U strncpy@@GLIBC_2.0
U strtol@@GLIBC_2.0
0000305c d __TMC_END__
00000f90 T write_provider_type
00001110 T write_serial_baud
00001060 T write_serial_device
00000930 t __x86.get_pc_thunk.bx
00000f18 t __x86.get_pc_thunk.cx
U __xstat@@GLIBC_2.0
To summarize: 1) Linking order in the gcc commands is correct (-llibname after -o blah.cpp) 2) Linker finds the library (libcanmpdconf.so) 3) Library is in the correct format for the platform (x86) 4) Library contains the symbol (see nm output)
There should be no reason, as far as I can tell, why there should be an undefined reference to any symbol that clearly exists in my library, which the linker can find. Does anybody know of any other ways I can try to troubleshoot this or what might be wrong ?
解决方案
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