A specific solution to the multiple definition of ' xxxxxx ' appears when the file is compiled _c language

Problem:
Originally has a single file tcpclient.c, run Gcc-o tcpclient tcpclient.c can successfully complete the compilation, and download to the target board tcpserver successful communication;
Now the tcpclient.c of the bottom part of the communication is extracted, placed in a single file nettrans.c, and Netrans.h as a header file;
Then, use the command

Copy Code code as follows:

Gcc-o tcpclient nettrans.c tcpclient.c

compilation, and can always be compiled successfully.
However, using makefile to compile, there are always the following multiple definition of class errors:

Copy Code code as follows:

dingq@u1110-120628:~/hwsvn/2sw/1prj_linux/pdu/src/branches/pdu-isocket/isocket$ make
GCC NETTRANS.O tcpclient.o-o tcpclient
tcpclient.o:in function ' NetTrans ':
/home/dingq/hwsvn/2sw/1prj_linux/pdu/src/branches/pdu-isocket/isocket/nettrans.c:30:multiple definition of ' NetTrans '
Nettrans.o:/home/dingq/hwsvn/2sw/1prj_linux/pdu/src/branches/pdu-isocket/isocket/nettrans.c:30:first defined Here
/USR/LIB/GCC/I686-LINUX-GNU/4.6.1/.. /.. /.. /i386-linux-gnu/crt1.o:in function ' _start ':
(. text+0x18): Undefined reference to ' main '
Collect2:ld returned 1 exit status
Make: * * * [client] Error 1

content of Makefile:

Copy Code code as follows:

CC = gcc
Cross_compile = arm-linux-
CROSS_CC = $ (cross_compile) gcc
Ccflags =-g3-wall-o0
Ldflags =
RM =-RM-RF
Src_client = NETTRANS.C tcpclient.c
Src_server = tcpserver.c
Obj_client = $ (SRC_CLIENT:%.C=%.O)
Obj_server = $ (SRC_SERVER:%.C=%.O)
. Phony:all
All:client
$ (obj_client): $ (src_client)
$ (CC) $ (ccflags)-C $<-O $@
$ (Obj_server): $ (src_server)
$ (CROSS_CC) $ (ccflags)-C $<-O $@
Client: $ (obj_client)
$ (CC) $ (ldflags) $ (obj_client)-O tcpclient
Server: $ (obj_server)
$ (CROSS_CC) $ (ldflags) $ (obj_server)-O tcpserver
. Phony:clean
Clean:
$ (RM) *.O tcpclient tcpserver

Solution:
1. The use of ordinary command compilation can be successful, but the use of makefile is not successful, indicating that the problem on the makefile;
Double-check the makefile specific compilation execution process:

Copy Code code as follows:

dingq@u1110-120628:~/hwsvn/2sw/1prj_linux/pdu/src/branches/pdu-isocket/isocket$ make Clean;make
RM-RF *.O tcpclient TCPServer
Gcc-g3-wall-o0-c Nettrans.c-o NETTRANS.O
Gcc-g3-wall-o0-c Nettrans.c-o TCPCLIENT.O
GCC NETTRANS.O tcpclient.o-o tcpclient
tcpclient.o:in function ' NetTrans ':
/home/dingq/hwsvn/2sw/1prj_linux/pdu/src/branches/pdu-isocket/isocket/nettrans.c:30:multiple definition of ' NetTrans '
Nettrans.o:/home/dingq/hwsvn/2sw/1prj_linux/pdu/src/branches/pdu-isocket/isocket/nettrans.c:30:first defined Here
/USR/LIB/GCC/I686-LINUX-GNU/4.6.1/.. /.. /.. /i386-linux-gnu/crt1.o:in function ' _start ':
(. text+0x18): Undefined reference to ' main '
Collect2:ld returned 1 exit status
Make: * * * [client] Error 1

The original generation NETTRANS.O and TCPCLIENT.O both use the same source file nettrans.c;
So, it's makefile.

Copy Code code as follows:

$ (obj_client): $ (src_client)
$ (CC) $ (ccflags)-C $<-O $@

There is a problem with this place, the pattern rule should be used to match the target file and the dependent file;
change makefile as follows:

Copy Code code as follows:

CC = gcc
Cross_compile = arm-linux-
CROSS_CC = $ (cross_compile) gcc
Ccflags =-g3-wall-o0
Ldflags =
RM =-RM-RF
Src_client = NETTRANS.C tcpclient.c
Src_server = tcpserver.c
Obj_client = $ (SRC_CLIENT:%.C=%.O)
. Phony:all
All:client
%.O:%.c
$ (CC) $ (ccflags)-C $<-O $@
Client: $ (obj_client)
$ (CC) $ (ldflags) $ (obj_client)-O tcpclient
Server: $ (obj_server)
$ (CROSS_CC) $ (ccflags)-C $ (src_server)-O $ (obj_server)
$ (CROSS_CC) $ (ldflags) $ (obj_server)-O tcpserver
. Phony:clean
Clean:
$ (RM) *.O tcpclient tcpserver

Recompile to successfully generate TcpClient.
solve the problem.