shared library plugin and calling functions from main program (Bluez)

Question

I am coding plugin for Bluez 5.18 in C, I want create my own BLE GATT profile as plugin (shared library). I need call function from main code, when I complile it, there is no error, but while loading plugin, it crash on undefined symbol - unsatisfied reference to function (for example gatt_service_add). But some functions are accessible from main program - all functions with prefix "btd_".

When I list symbols from main program using nm program, functions with prefix "btd_" are global symbols (T mark in list) and functions as "gatt_service_add" is local symbol (t mark in list)

So my question is, how can I use functions like "gatt_service_add" in my plugin without undefined symbol error? Am I missing some parameters while compiling? Note that I cant change main program, so I need solution only for my plugin. Using only functions with "btd_" prefix I dont know how to create working own gatt profile etc... so acceptable solution can be also working gatt profile only with accessible functions ("btd_" prefix + some help functions from /lib)

I complile my plugin with this parameters:

gcc -DHAVE_CONFIG_H -I/usr/include/glib-2.0 -I/usr/include/dbus-1.0 -I/usr/include/bluetooth -I/usr/lib/dbus-1.0/include -I/usr/lib/glib-2.0/include -I"/home/<user>/Workspace/bluez" -O3 -Wall -c -fmessage-length=0 -fPIC -MMD -MP -MF"gatt-example.d" -MT"gatt-example.d" -o "gatt-example.o" "../gatt-example.c"
gcc -Wl,-E -shared -o "bluez-plugin.so"  ./gatt-example.o  /home/<user>/Workspace/bluez/lib/.libs/libbluetooth-internal.a -ldbus-1 -lglib-2.0

Answer 1

For now, you cant create BLE GATT profile as external plugin in Bluez 5.18 (also in 5.19), and it is only possible using builtin plugin

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Answer 2

Local symbols cannot be accessed by other modules. That's the very definition of local symbols. You are missing no compiler flags, it's just not possible.