Wireshark · Wireshark-dev: [Wireshark-dev] how to use the wireshark source code to develop application?

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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!