How to Compile Asterisk module like (app_Voicemail.c)

First :

At starting of the file add this lines

#ifndef AST_MODULE
#define AST_MODULE "app_voicemail"
#endif

AFTER THAT COMPILE THE MODULE

cd /usr/src/asterisk-1.6.1.8/apps/

gcc -shared app_voicemail.c -o app_voicemail.so

cp app_voicemail.so /usr/lib/asterisk/modules/

CLI> restart now