[Dragokas]

https://github.com/alliedmodders/sou...onSys.cpp#L170
https://github.com/alliedmodders/sou...k_ext.cpp#L106
https://github.com/alliedmodders/sou...xtension.h#L40

Possible,

#include "smsdk_ext.h"

or

SMEXT_LINK(&g_Sample);

is missing.

/** 
 * @brief Exposes plugin's main interface.
 */
#define SMEXT_LINK(name) SDKExtension *g_pExtensionIface = name;

https://wiki.alliedmods.net/Writing_...Sample_Project