不同 gtk 主题，滚动条问题

我现在在学习GTK+，但是装好gtk+之后，编译出错，编译命令是gcc `pkg-config --cflags --libs gtk+-3.0` -o demo demo.c

demo.c:(.text+0x1f): undefined reference to `gtk_init'
demo.c:(.text+0x29): undefined reference to `gtk_window_new'
demo.c:(.text+0x32): undefined reference to `gtk_window_get_type'
demo.c:(.text+0x44): undefined reference to `g_type_check_instance_cast'
demo.c:(.text+0x51): undefined reference to `gtk_window_set_title'
demo.c:(.text+0x56): undefined reference to `gtk_container_get_type'
demo.c:(.text+0x68): undefined reference to `g_type_check_instance_cast'
demo.c:(.text+0x75): undefined reference to `gtk_container_set_border_width'
demo.c:(.text+0x8b): undefined reference to `g_type_check_instance_cast'
demo.c:(.text+0xac): undefined reference to `g_signal_connect_data'
demo.c:(.text+0xb8): undefined reference to `gtk_widget_show_all'
demo.c:(.text+0xbd): undefined reference to `gtk_main'
/tmp/ccIrR4KQ.o: In function `destroy':
demo.c:(.text+0xde): undefined reference to `gtk_main_quit'
collect2: ld 返回 1


到底是哪里出错了，大侠们帮帮忙