Using google protobuf with Qt Creator

VimHar

@blah900 hey. What have you done that made things work. I have installed protobuf using vcpkg and pointing to the static library same as you did in windows.

Except lptotobuf im using llibprotouf. Still facing the undefined erro.

jsulm

@VimHar said in Using google protobuf with Qt Creator:

Except lptotobuf im using llibprotouf

How do you link libprotobuf?

VimHar

@jsulm

LIBS += -LC:/vcpkg/installed/x64-windows/lib/ -llibprotobuf

like this

jsulm

@VimHar said in Using google protobuf with Qt Creator:

-llibprotobuf

-lprotobuf

VimHar

@jsulm Have done that. It says
:-1: error: cannot find -lprotobuf

My files in lib folder are libprotobuf.lib , libprotobuf-lite.lib , libprotoc.lib

jsulm

@VimHar On windows you need libprotobuf.lib to link at build time - do you have it?

VimHar

@jsulm Yes as stated I have these files in lib folder of the path specified,
libprotobuf.lib , libprotobuf-lite.lib , libprotoc.lib

My .pro file

QT += core gui

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

CONFIG += c++17

INCLUDEPATH += C:\vcpkg\installed\x64-windows\include\

LIBS += -LC:/vcpkg/installed/x64-windows/lib/ -lprotobuf

SOURCES +=
main.cpp
mainwindow.cpp
m.pb.cc

HEADERS +=
mainwindow.h
m.pb.h

FORMS +=
mainwindow.ui

jsulm

@VimHar said in Using google protobuf with Qt Creator:

-lprotobuf

Try

-llibprotobuf.lib

VimHar

@jsulm No same error. Cannot find llibprotouf.lib

JonB

@VimHar
There have been inconsistencies in the spellings of what you have typed in your various posts. Why don't you try:

LIBS += C:\vcpkg\installed\x64-windows\lib\libprotobuf.lib

Please use copy & paste of above line. If you get error please copy & paste exact text back here.

VimHar

@JonB said in Using google protobuf with Qt Creator:

LIBS += C:\vcpkg\installed\x64-windows\lib\libprotobuf.lib

QT += core gui

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

CONFIG += c++17

INCLUDEPATH += C:\vcpkg\installed\x64-windows\include\

LIBS += C:\vcpkg\installed\x64-windows\lib\libprotobuf.lib

SOURCES +=
main.cpp
mainwindow.cpp
m.pb.cc

HEADERS +=
mainwindow.h
m.pb.h

FORMS +=
mainwindow.ui

Sorry for the same. Even then Im getting the same undefined error faced by the actual questioner.
i.e "undefined reference to `google::protobuf::internal::AssignDescriptors(google::protobuf::internal::DescriptorTable const*, bool)''

jsulm

@VimHar Was the Protobuf lib built using same compiler? What compiler do you use to build your app?

JonB

@VimHar said in Using google protobuf with Qt Creator:

Even then Im getting the same undefined error faced by the actual questioner.
i.e "undefined reference to `google::protobuf::internal::AssignDescriptors(google::protobuf::internal::DescriptorTable const*, bool)''

Now I do not understand, because this is not the same error at all as you said you were having. You said you got one of:

. :-1: error: cannot find -lprotobuf
Cannot find llibprotouf.lib

These errors mean it could not find the library file to link with --- which is why I wanted to get you to type in the full path --- where the error now is that the library file is found, but you have an unresolved reference. Quite different kinds of error.

I think/suspect the lib file is being found but is the wrong version or built with the wrong compiler or something like that.... Please start by answering @jsulm's question with your best information.

VimHar

hey Thanks..JonB.. The actual intention of mine is the "undefined error" only.
Regarding compilers, I used vcpkg for installing protobuf and Qt uses MinGw64.

Is this the problem??

jsulm

@VimHar said in Using google protobuf with Qt Creator:

Is this the problem??

Probably.
There should be a linker warning in the build log.

JonB

@VimHar said in Using google protobuf with Qt Creator:

I used vcpkg for installing protobuf and Qt uses MinGw64.

I don't know what "vcpkg" is (MSVC??) but it sounds like a different compiler/linker. MinGW library files end in .a not .lib, maybe that is the cause of the "cannot find library" messages? In any case you need to use the smae compiler/linker for everything.

VimHar

Hey,.. Great. I have done re-installing protobuf using Msys following the steps below
https://stackoverflow.com/a/73287395/10432503

Now I can able to run using plain g++ command in the terminal.

But when I do the same in QT , the following error occurs
:-1: error: Dwarf Error: Can't find .debug_ranges section.

My .pro file
QT += core gui

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

CONFIG += c++17

INCLUDEPATH += C:/protobuf-3.21.11/src

LIBS += -LC:/protobuf-3.21.11/src/.libs -lprotobuf

SOURCES +=
main.cpp
mainwindow.cpp
m.pb.cc

HEADERS +=
mainwindow.h
m.pb.h

FORMS +=
mainwindow.ui

Should I add anything more.?

VimHar

Hey Jon,

Im also sharing you the compiler definitions.

Im using

The g++ command works smoothly. But I'm getting this new error when I compile using QT.
FYI, I have two MinGWs one inside QT folder and one inside Msys folder.

Am I missing any? :(

JonB

@VimHar
I know nothing about this area. ":-1: error: Dwarf Error: Can't find .debug_ranges section." implies to me you have incompatible compilers or incompatible options or something.

VimHar

What you said is right. Thanks Jon. Reach out incase you got any. I will try.