how to use the wireshark source code to develop application?

["??????????" <237825552 () qq com>]

I want to store some information about packets and transmit among files,so i create a file in wireshark root 
directory,named performance.h:


//performance.h
#include <glib.h>
typedef struct performance_s
{
        gfloat time[100];
        gfloat delay[100];
        guint32 packetSize[100];
        guint32 payload;
        guint32 index;
        guint32 temp_size;
        gfloat temp_time;
}performance;
extern peformance* performance_test;



in the file ,i declare a struct and declare a pointer to it,then i want to use the variable "performance_test" in file 
wiretap/libpcap.c, epan/dissectors/packet-ieee80211.c,so i define the variable "peformance_test" in performance.c in 
wireshark root directory  and include the head file in wiretap/libpcap.c, epan/dissectors/packet-ieee80211.c ,but once 
i use the variable in these two files,when i compile the wireshark project,it come up with one error:undefined 
reference to 'peformance_test'.


it looks like the variable peformance_test should be defined and used in the same file ,if i want to use it in 
different files,i think i should modify the makefile.common to change the compile process ,but i don't know how .could 
someone help me fix it,please!

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