use G_BEGIN_DECLS/G_END_DECLS.
#if defined(SUPPORT_VIEWER) G_BEGIN_DECLS void viewmem_read(VIEWMEM_T *cfg, UINT32 adrs, BYTE *buf, UINT32 size); void viewmem_write(VIEWMEM_T *cfg, UINT32 adrs, BYTE *buf, UINT32 size); G_END_DECLS #endif