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  4. Generate a makefile without a main function from Qmake - "undefined reference to `main' "

Generate a makefile without a main function from Qmake - "undefined reference to `main' "

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  • N Offline
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    NikoBir
    wrote on 8 Nov 2022, 10:15 last edited by
    #3

    Thanks for your answer, yes it's my pro file that I want to build.
    I added TEMPLATE += lib because I read that I need to use this variable if I want to build without a main function.

    J 1 Reply Last reply 8 Nov 2022, 11:47
    0
    • N NikoBir
      8 Nov 2022, 10:15

      Thanks for your answer, yes it's my pro file that I want to build.
      I added TEMPLATE += lib because I read that I need to use this variable if I want to build without a main function.

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      jsulm
      Lifetime Qt Champion
      wrote on 8 Nov 2022, 11:47 last edited by
      #4

      @NikoBir said in Generate a makefile without a main function from Qmake - "undefined reference to `main' ":

      I added TEMPLATE += lib because I read that I need to use this variable if I want to build without a main function

      That is clear. My question is whether you had something else there and then changed to lib. If that's the case then delete everything in build folder, run qmake and build.

      https://forum.qt.io/topic/113070/qt-code-of-conduct

      S 1 Reply Last reply 8 Nov 2022, 20:24
      0
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        NikoBir
        wrote on 8 Nov 2022, 12:14 last edited by
        #5

        Ah ! I misunderstood ! Yes, I had nothing before. I even didn't had a TEMPLATE variable.
        Like you said I removed everything in the build folder, ran qmake and built but I have the same issue.

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        • N NikoBir
          8 Nov 2022, 09:46

          Hello everyone !

          I'm currently trying to generate protobuf files with qmake.
          But when I execute the makefile, I have :

          • My correctly generated protobuf files (yes !).
          • An error : "undefined reference to `main' "

          I don't want to have a main function, I just want to generate some files. So, I don't need to have a main function .... But Qmake really want it....
          How can I explain him that it's just fine and cool ?

          I tested to change my TEMPLATE in my .pro but it changes nothing ...

          These files are in the same folder :

          My .pro :

          QT -= gui
          TEMPLATE += lib
          INCLUDEPATH += /usr/include/
          LIBS += /usr/lib/libprotobuf.so
          PROTOS = comGRPC.proto
          include(protobuf.pri)
          

          My .pri :

          PROTOPATH += .
          PROTOPATH += ../Protocol
          PROTOPATHS =
          for(p, PROTOPATH):PROTOPATHS += --proto_path=$${p}
          
          protobuf_decl.name = protobuf header
          protobuf_decl.input = PROTOS
          protobuf_decl.output = ${QMAKE_FILE_BASE}.pb.h
          protobuf_decl.commands = /usr/bin/protoc --cpp_out="." $${PROTOPATHS} ${QMAKE_FILE_NAME}
          protobuf_decl.variable_out = GENERATED_FILES
          QMAKE_EXTRA_COMPILERS += protobuf_decl
          
          protobuf_impl.name = protobuf implementation
          protobuf_impl.input = PROTOS
          protobuf_impl.output = ${QMAKE_FILE_BASE}.pb.cc
          protobuf_impl.depends = ${QMAKE_FILE_BASE}.pb.h
          protobuf_impl.commands = $$escape_expand(\n)
          protobuf_impl.variable_out = GENERATED_SOURCES
          QMAKE_EXTRA_COMPILERS += protobuf_impl
          
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          jsulm
          Lifetime Qt Champion
          wrote on 8 Nov 2022, 12:18 last edited by
          #6

          @NikoBir said in Generate a makefile without a main function from Qmake - "undefined reference to `main' ":

          LIBS += /usr/lib/libprotobuf.so

          This line is wrong please seee here how to do it properly: https://doc.qt.io/qt-6/qmake-variable-reference.html#libs), but not the cause for your issue I think.
          Can you provide a minimal reproducible project, so others can try?

          https://forum.qt.io/topic/113070/qt-code-of-conduct

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            NikoBir
            wrote on 8 Nov 2022, 13:11 last edited by
            #7

            Thank you, yes I can !
            I created this repository with my zipped project. I added the includes and libs.

            https://github.com/QtForumHelp/undefined_reference_to_main_Qmake-Protobuf

            J 1 Reply Last reply 8 Nov 2022, 13:20
            0
            • N NikoBir
              8 Nov 2022, 13:11

              Thank you, yes I can !
              I created this repository with my zipped project. I added the includes and libs.

              https://github.com/QtForumHelp/undefined_reference_to_main_Qmake-Protobuf

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              jsulm
              Lifetime Qt Champion
              wrote on 8 Nov 2022, 13:20 last edited by
              #8

              @NikoBir I will check (it does not build for me). But your LIBS is still wrong...

              https://forum.qt.io/topic/113070/qt-code-of-conduct

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                NikoBir
                wrote on 8 Nov 2022, 13:38 last edited by
                #9

                Ok I will correct it !

                1 Reply Last reply
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                • J jsulm
                  8 Nov 2022, 11:47

                  @NikoBir said in Generate a makefile without a main function from Qmake - "undefined reference to `main' ":

                  I added TEMPLATE += lib because I read that I need to use this variable if I want to build without a main function

                  That is clear. My question is whether you had something else there and then changed to lib. If that's the case then delete everything in build folder, run qmake and build.

                  S Offline
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                  SGaist
                  Lifetime Qt Champion
                  wrote on 8 Nov 2022, 20:24 last edited by SGaist 11 Oct 2022, 19:29
                  #10

                  Hi,

                  @jsulm said in Generate a makefile without a main function from Qmake - "undefined reference to `main' ":

                  @NikoBir said in Generate a makefile without a main function from Qmake - "undefined reference to `main' ":

                  I added TEMPLATE += lib because I read that I need to use this variable if I want to build without a main function

                  That is clear. My question is whether you had something else there and then changed to lib. If that's the case then delete everything in build folder, run qmake and build.

                  In addition to what @jsulm, TEMPLATE should contain a single value. Here you likely have something else. So just in case, replace it with TEMPLATE = lib.

                  Interested in AI ? www.idiap.ch
                  Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

                  P 1 Reply Last reply 10 Nov 2022, 09:58
                  3
                  • S SGaist
                    8 Nov 2022, 20:24

                    Hi,

                    @jsulm said in Generate a makefile without a main function from Qmake - "undefined reference to `main' ":

                    @NikoBir said in Generate a makefile without a main function from Qmake - "undefined reference to `main' ":

                    I added TEMPLATE += lib because I read that I need to use this variable if I want to build without a main function

                    That is clear. My question is whether you had something else there and then changed to lib. If that's the case then delete everything in build folder, run qmake and build.

                    In addition to what @jsulm, TEMPLATE should contain a single value. Here you likely have something else. So just in case, replace it with TEMPLATE = lib.

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                    Paul Colby
                    wrote on 10 Nov 2022, 09:58 last edited by
                    #11

                    @SGaist wrote:

                    TEMPLATE should contain a single value. Here you likely something else. So just in case, replace it with TEMPLATE = lib.

                    Indeed, as per the docs, TEMPLATE defaults to app. So by using += the TEMPLATE ends up being app lib, which is not what you want :)

                    So, as @SGaist indicated, drop the + from that line so:

                    TEMPLATE = lib
                    

                    Cheers.

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                      NikoBir
                      wrote on 10 Nov 2022, 15:01 last edited by
                      #12

                      Thank you all ! It worked !!!!!

                      Yes the solution was TEMPLATE = lib !

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                      10 Nov 2022, 15:01

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