Re: [lwip-users] Errors during build of lwip in Windows

[Giuseppe Modugno]

Il 15/04/2023 01:58, Giuseppe Modugno ha scritto:
[...]
> Now I enabled LWIP_MQTT_APP and I receive the following errors during 
> build:
>
> [ 99%] Linking C executable example_app.exe
> liblwipcontribexamples.a(mqtt_example.obj): In function 
> `mqtt_connection_cb':
> C:/temp/lwip/contrib/examples/mqtt/mqtt_example.c:100: undefined 
> reference to `mqtt_sub_unsub'
> C:/temp/lwip/contrib/examples/mqtt/mqtt_example.c:104: undefined 
> reference to `mqtt_sub_unsub'
> liblwipcontribexamples.a(mqtt_example.obj): In function 
> `mqtt_example_init':
> C:/temp/lwip/contrib/examples/mqtt/mqtt_example.c:116: undefined 
> reference to `mqtt_client_new'
> C:/temp/lwip/contrib/examples/mqtt/mqtt_example.c:118: undefined 
> reference to `mqtt_set_inpub_callback'
> C:/temp/lwip/contrib/examples/mqtt/mqtt_example.c:123: undefined 
> reference to `mqtt_client_connect'
> collect2.exe: error: ld returned 1 exit status
> mingw32-make.exe[2]: *** [CMakeFiles\example_app.dir\build.make:128: 
> example_app.exe] Error 1
> mingw32-make.exe[1]: *** [CMakeFiles\Makefile2:358: 
> CMakeFiles/example_app.dir/all] Error 2
> mingw32-make.exe: *** [Makefile:135: all] Error 2
>
> I couldn't understand why, because mqtt.c is really compiled and linked 
> in liblwipallapps.a.

I think I understood. In CMakeLists.txt there's the following line:

target_link_libraries(example_app ${LWIP_SANITIZER_LIBS} lwipallapps 
lwipcontribexamples lwipcontribapps lwipcontribaddons 
lwipcontribportwindows lwipcore lwipmbedtls)

I don't know exactly why, but the problem disappeared in my build system 
after postponing lwipallapps, such as:

target_link_libraries(example_app ${LWIP_SANITIZER_LIBS} 
lwipcontribexamples lwipallapps lwipcontribapps lwipcontribaddons 
lwipcontribportwindows lwipcore lwipmbedtls)


> Lastly another strange behaviour. If I enable LWIP_HTTPD_APP, the build 
> process is ok, but I can't see the web page on the browser when I type 
> the URL http://192.168.1.200.
[...]

I suspect there's a problem with WinPcap libraries. If I try to connect 
to the http server from another machine, it works. Even ping to lwip 
doesn't work from the Windows host machine.

Do you know how this can be solved?