undefined reference to `SetPduPowerConsumptionCnt'的解决办法
问题：
程序模型用C++语言编写，在程序模型和调用函数之间添加了一个接口文件modelc.cpp，用来让用c语言程序调用程序模型中的函数；
新添加了两个函数setPduPowerConsumptionCnt()和setPduPowerConsumptionTot()，用来清除PDU模型中的总功耗和功耗计数器；
编译时出现错误提示：
dingq@wd-u1110:~/hwsvn/2sw/1prj_linux/pdu/src/branches/pdu-isocket$ make clean;make rm -f *.o pdu arm-linux-g++ -g3 -Wall -o0 -I../../../tools/eldk42/arm/usr/include/ -I../../../tools/eldk42/arm/usr/include/C++/4.2.2/ -c main.cpp -o main.o arm-linux-g++ -g3 -Wall -o0 -I../../../tools/eldk42/arm/usr/include/ -I../../../tools/eldk42/arm/usr/include/C++/4.2.2/ -c model.cpp -o model.o arm-linux-g++ -g3 -Wall -o0 -I../../../tools/eldk42/arm/usr/include/ -I../../../tools/eldk42/arm/usr/include/C++/4.2.2/ -c modelc.cpp -o modelc.o arm-linux-g++ -g3 -Wall -o0 -I../../../tools/eldk42/arm/usr/include/ -I../../../tools/eldk42/arm/usr/include/C++/4.2.2/ -c IniFile.cpp -o IniFile.o arm-linux-g++ -g3 -Wall -o0 -I../../../tools/eldk42/arm/usr/include/ -I../../../tools/eldk42/arm/usr/include/C++/4.2.2/ -c ClientSocket.cpp -o ClientSocket.o arm-linux-g++ -g3 -Wall -o0 -I../../../tools/eldk42/arm/usr/include/ -I../../../tools/eldk42/arm/usr/include/C++/4.2.2/ -c Thread.cpp -o Thread.o arm-linux-g++ -g3 -Wall -o0 -I../../../tools/eldk42/arm/usr/include/ -I../../../tools/eldk42/arm/usr/include/C++/4.2.2/ -c SensorReader.cpp -o SensorReader.o arm-linux-g++ -g3 -Wall -o0 -I../../../tools/eldk42/arm/usr/include/ -I../../../tools/eldk42/arm/usr/include/C++/4.2.2/ -c LcdWriter.cpp -o LcdWriter.o arm-linux-g++ -g3 -Wall -o0 -I../../../tools/eldk42/arm/usr/include/ -I../../../tools/eldk42/arm/usr/include/C++/4.2.2/ -c Monitor.cpp -o Monitor.o arm-linux-g++ -g3 -Wall -o0 -I../../../tools/eldk42/arm/usr/include/ -I../../../tools/eldk42/arm/usr/include/C++/4.2.2/ -c Helper.cpp -o Helper.o arm-linux-g++ -g3 -Wall -o0 -I../../../tools/eldk42/arm/usr/include/ -I../../../tools/eldk42/arm/usr/include/C++/4.2.2/ -c Mutex.cpp -o Mutex.o arm-linux-g++ -g3 -Wall -o0 -I../../../tools/eldk42/arm/usr/include/ -I../../../tools/eldk42/arm/usr/include/C++/4.2.2/ -c serial.cpp -o serial.o arm-linux-gcc -g3 -Wall -o0 -c frm_package.c -o frm_package.o arm-linux-gcc -g3 -Wall -o0 -c nettrans.c -o nettrans.o arm-linux-gcc -g3 -Wall -o0 -c sensor-att7053.c -o sensor-att7053.o arm-linux-g++ -L../../../tools/lib/ -lpthread -o pdu main.o model.o modelc.o IniFile.o ClientSocket.o Thread.o SensorReader.o LcdWriter.o Monitor.o Helper.o Mutex.o serial.o frm_package.o nettrans.o sensor-att7053.o sensor-att7053.o: In function `reset_EnergyPort': /home/dingq/hwsvn/2sw/1prj_linux/pdu/src/branches/pdu-isocket/sensor-att7053.c:83: undefined reference to `SetPduPowerConsumptionCnt' /home/dingq/hwsvn/2sw/1prj_linux/pdu/src/branches/pdu-isocket/sensor-att7053.c:92: undefined reference to `SetPduPowerConsumptionTot' collect2: ld returned 1 exit status make: *** [pdu] Error 1
解决办法：
1. 忘了在modelc.cpp的函数实现中添加extern "C"了。
extern "C" int setPduPowerConsumptionCnt(int index, unsigned int val) {
if (index > 8 || index < 1) {
printf("Error: The index available is between 1 and 8.\n");
return -1;
}
model->Channels()[index-1].TheEnergyPort().SetPowerConsumptionCount(val);
return 0;
}
添加之后，再次编译，错误仍然存在。
查找了半天，原来头文件modelc.h中和实现文件modelc.cpp中的函数名差了一个符号，头文件中是小写的s，setPduPowerConsumptionCnt，而实现文件中用了大写的S，SetPduPowerConsumptionCnt；而使用vim编辑器时，没有设定区分大小写，导致没有很容易一眼看出来。
修改之后，成功编译。
问题解决。
