How does g++ link an objective file .o built by gcc?

[Dingjun Chen <Dingjun.Chen@geotechairborne.com>]

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HI, everyone,

I have a question for you.

I have multiple c++ files .cc (main program is C++) and one c file 'librtd-dm6620.c'. Of course I will use g++ to build the executable. For that 'librtd-dm6620.c' file I still want to build its .o file via gcc because there are some possibly fatal warnings if I use g++ to build this .c file. If this .c file is built with gcc, there is no any warning and it is perfect in compilation.

Finally, I want to build the executable by linking all .o files via g++.  The problem is that the .o file built by gcc is not really linked by g++.  All defined functions in 'librtd-dm6620.c' cannot be found by the g++ linker 'ld'.

I use CMake to build the executable. Could someone tell me how to link an objective file built by gcc into C++ executable? Did I miss some special compiling options for the c file 'librtd-dm6620.c'?

Please see the error information in the file attached for details.

I look forward to your help and hearing from you.

Thanks & Regards,

Dingjun
Dingjun Chen  | Software Developer

[Geotech Airborne Geophysical Surveys]

Geotech Ltd. dba Geotech Airborne | 270 INDUSTRIAL PKY S | AURORA ON CA | L4G 3T9
T: +1 905 841 5004 | Dingjun.Chen@geotechairborne.com<mailto:Dingjun.Chen@geotechairborne.com> | www.geotechairborne.com<www.geotech.ca>

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Scanning dependencies of target vtem_xyz
[  4%] Building CXX object CMakeFiles/vtem_xyz.dir/src/adcGS.cc.o
[  8%] Building CXX object CMakeFiles/vtem_xyz.dir/src/c_8x16.cc.o
[ 12%] Building CXX object CMakeFiles/vtem_xyz.dir/src/dac6620.cc.o
[ 16%] Building CXX object CMakeFiles/vtem_xyz.dir/src/dongle_interface.cc.o
[ 20%] Building CXX object CMakeFiles/vtem_xyz.dir/src/emstream.cc.o
[ 25%] Building CXX object CMakeFiles/vtem_xyz.dir/src/fmenu.cc.o
[ 29%] Building CXX object CMakeFiles/vtem_xyz.dir/src/frqdom.cc.o
[ 33%] Building CXX object CMakeFiles/vtem_xyz.dir/src/gmenu.cc.o
[ 37%] Building CXX object CMakeFiles/vtem_xyz.dir/src/graph.cc.o
[ 41%] Building CXX object CMakeFiles/vtem_xyz.dir/src/gsc24dsi_interface.cc.o
[ 45%] Building CXX object CMakeFiles/vtem_xyz.dir/src/keybrd.cc.o
[ 50%] Building CXX object CMakeFiles/vtem_xyz.dir/src/mouse.cc.o
[ 54%] Building CXX object CMakeFiles/vtem_xyz.dir/src/processdngl.cc.o
[ 58%] Building CXX object CMakeFiles/vtem_xyz.dir/src/processxyz.cc.o
[ 62%] Building CXX object CMakeFiles/vtem_xyz.dir/src/runproc.cc.o
[ 66%] Building CXX object CMakeFiles/vtem_xyz.dir/src/serialmsg.cc.o
[ 70%] Building CXX object CMakeFiles/vtem_xyz.dir/src/simulant.cc.o
[ 75%] Building CXX object CMakeFiles/vtem_xyz.dir/src/systemid.cc.o
[ 79%] Building CXX object CMakeFiles/vtem_xyz.dir/src/Vtem24.cc.o
[ 83%] Building CXX object CMakeFiles/vtem_xyz.dir/src/_d_aes.cc.o
[ 87%] Building CXX object CMakeFiles/vtem_xyz.dir/src/_d_hexbin.cc.o
[ 91%] Building CXX object CMakeFiles/vtem_xyz.dir/src/_d_serial.cc.o
[ 95%] Building C object CMakeFiles/vtem_xyz.dir/src/librtd-dm6620.c.o
[100%] Linking CXX executable ../bin/vtem_xyz
CMakeFiles/vtem_xyz.dir/src/dac6620.cc.o(.text+0x576): In function `OpenDAC()':
: undefined reference to `OpenBoard6620(DM6620_Board_Descriptor**, int)'
CMakeFiles/vtem_xyz.dir/src/dac6620.cc.o(.text+0x5b1): In function `StartDAC()':
: undefined reference to `SetDACUpdateEnable6620(DM6620_Board_Descriptor*, int, int, int, int)'
CMakeFiles/vtem_xyz.dir/src/dac6620.cc.o(.text+0x5be): In function `StartDAC()':
: undefined reference to `DoneTimer6620(DM6620_Board_Descriptor*)'
CMakeFiles/vtem_xyz.dir/src/dac6620.cc.o(.text+0x5cb): In function `StartDAC()':
: undefined reference to `InitBoard6620(DM6620_Board_Descriptor*)'
CMakeFiles/vtem_xyz.dir/src/dac6620.cc.o(.text+0x5e0): In function `StartDAC()':
: undefined reference to `SelectTimerCounter6620(DM6620_Board_Descriptor*, DM6620HR_TIMER_SEL)'
CMakeFiles/vtem_xyz.dir/src/dac6620.cc.o(.text+0x5fd): In function `StartDAC()':
: undefined reference to `ClockDivisor6620(DM6620_Board_Descriptor*, DM6620HR_CLK, unsigned short)'
CMakeFiles/vtem_xyz.dir/src/dac6620.cc.o(.text+0x61a): In function `StartDAC()':
: undefined reference to `SetDACRange6620(DM6620_Board_Descriptor*, DM6620HR_DAC, DM6620HR_DAC_RANGE)'
CMakeFiles/vtem_xyz.dir/src/dac6620.cc.o(.text+0x637): In function `StartDAC()':
: undefined reference to `SetDACRange6620(DM6620_Board_Descriptor*, DM6620HR_DAC, DM6620HR_DAC_RANGE)'
CMakeFiles/vtem_xyz.dir/src/dac6620.cc.o(.text+0x654): In function `StartDAC()':
: undefined reference to `SetDACUpdate6620(DM6620_Board_Descriptor*, DM6620HR_DAC, DM6620HR_DAC_UPDATE)'
CMakeFiles/vtem_xyz.dir/src/dac6620.cc.o(.text+0x671): In function `StartDAC()':
: undefined reference to `SetDACUpdate6620(DM6620_Board_Descriptor*, DM6620HR_DAC, DM6620HR_DAC_UPDATE)'
CMakeFiles/vtem_xyz.dir/src/dac6620.cc.o(.text+0x6b1): In function `StartDAC()':
: undefined reference to `FillDACFIFO6620(DM6620_Board_Descriptor*, DM6620HR_DAC, unsigned short, unsigned short)'
CMakeFiles/vtem_xyz.dir/src/dac6620.cc.o(.text+0x6f8): In function `StartDAC()':
: undefined reference to `FillDACFIFO6620(DM6620_Board_Descriptor*, DM6620HR_DAC, unsigned short, unsigned short)'
CMakeFiles/vtem_xyz.dir/src/dac6620.cc.o(.text+0x71c): In function `StartDAC()':
: undefined reference to `SetDACCycle6620(DM6620_Board_Descriptor*, DM6620HR_DAC, DM6620HR_DAC_CYCLE)'
CMakeFiles/vtem_xyz.dir/src/dac6620.cc.o(.text+0x739): In function `StartDAC()':
: undefined reference to `SetDACCycle6620(DM6620_Board_Descriptor*, DM6620HR_DAC, DM6620HR_DAC_CYCLE)'
CMakeFiles/vtem_xyz.dir/src/dac6620.cc.o(.text+0x766): In function `StartDAC()':
: undefined reference to `SetDACUpdateEnable6620(DM6620_Board_Descriptor*, int, int, int, int)'
CMakeFiles/vtem_xyz.dir/src/dac6620.cc.o(.text+0x78b): In function `StopDAC()':
: undefined reference to `SetDACCycle6620(DM6620_Board_Descriptor*, DM6620HR_DAC, DM6620HR_DAC_CYCLE)'
CMakeFiles/vtem_xyz.dir/src/dac6620.cc.o(.text+0x7a8): In function `StopDAC()':
: undefined reference to `SetDACCycle6620(DM6620_Board_Descriptor*, DM6620HR_DAC, DM6620HR_DAC_CYCLE)'
CMakeFiles/vtem_xyz.dir/src/dac6620.cc.o(.text+0x7d5): In function `StopDAC()':
: undefined reference to `SetDACUpdateEnable6620(DM6620_Board_Descriptor*, int, int, int, int)'
CMakeFiles/vtem_xyz.dir/src/dac6620.cc.o(.text+0x7fa): In function `StopDAC()':
: undefined reference to `FillDACFIFO6620(DM6620_Board_Descriptor*, DM6620HR_DAC, unsigned short, unsigned short)'
CMakeFiles/vtem_xyz.dir/src/dac6620.cc.o(.text+0x81f): In function `StopDAC()':
: undefined reference to `FillDACFIFO6620(DM6620_Board_Descriptor*, DM6620HR_DAC, unsigned short, unsigned short)'
CMakeFiles/vtem_xyz.dir/src/dac6620.cc.o(.text+0x834): In function `StopDAC()':
: undefined reference to `UpdateDAC6620(DM6620_Board_Descriptor*, DM6620HR_DAC)'
CMakeFiles/vtem_xyz.dir/src/dac6620.cc.o(.text+0x849): In function `StopDAC()':
: undefined reference to `UpdateDAC6620(DM6620_Board_Descriptor*, DM6620HR_DAC)'
CMakeFiles/vtem_xyz.dir/src/dac6620.cc.o(.text+0x85f): In function `CloseDAC()':
: undefined reference to `CloseBoard6620(DM6620_Board_Descriptor*)'
collect2: ld returned 1 exit status
make[2]: *** [CMakeFiles/vtem_xyz.dir/build.make:667: ../bin/vtem_xyz] Error 1
make[1]: *** [CMakeFiles/Makefile2:68: CMakeFiles/vtem_xyz.dir/all] Error 2
make: *** [Makefile:84: all] Error 2