Multiple definition of '__imp___C_specific_handler'

[pingal]

I'm facing some compilation issues as I've migrated my working cpp-project from VS to QT. The app is using low-level windows sockets API's. In one of my header file I've used struct addrinfo which requires

#include <ws2tcpip.h>

Due to which I'm getting these errors

If I comment this include, the compiler doesn't recognize struct addrinfo as shown below

Here is my .pro file

QT += quick

CONFIG += c++17

DEFINES += _WIN32_WINNT=0x0602
LIBS += -LC:/Windows/System32 -lWs2_32
# You can make your code fail to compile if it uses deprecated APIs.
# In order to do so, uncomment the following line.
#DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000    # disables all the APIs deprecated before Qt 6.0.0

SOURCES += \
        ClientResponse.cpp \
        Listen.cpp \
        ServerQueries.cpp \
        base64.cpp \
        client.cpp \
        clientlistwrapper.cpp \
        main.cpp \

RESOURCES += qml.qrc

# Additional import path used to resolve QML modules in Qt Creator's code model
QML_IMPORT_PATH =

# Additional import path used to resolve QML modules just for Qt Quick Designer
QML_DESIGNER_IMPORT_PATH =

# Default rules for deployment.
qnx: target.path = /tmp/$${TARGET}/bin
else: unix:!android: target.path = /opt/$${TARGET}/bin
!isEmpty(target.path): INSTALLS += target

HEADERS += \
    ClientResponse.h \
    Listen.h \
    ServerQueries.h \
    base64.h \
    client.h \
    clientlistwrapper.h \
    thread_args.h

FORMS +=

DISTFILES +=

P.S: The same projects builds and run on VS flawlessly.

[JonB]

@pingal
This is only a hunch. Your "undefined references" look like symbols from MSVC compiler to me, while you seem to be using MinGW for your compiler/linker?

[pingal]

![a0fc3fc0-7aa0-4f3c-bd37-2a0b773ef31e-image.png](https://ddgobkiprc33d.cloudfront.net

I'm using MinGW compiler in QT

[JonB]

@pingal
I know you are. The question is about your use of -lWs2_32. Does that pull in a .a file (MinGW) or a .lib file (MSVC)? Does that have a runtime .DLL file which is MSVC or MinGW? Does the .DLL have any further unsatisfied dependencies?

Another possibility: you are using 64-bit MinGW. Are you building for 32- or 64-bit? If 64-bit, does -lWs2_32 target 32-bit? Does e.g. https://stackoverflow.com/questions/35003396/mingw-w64-searches-for-libws2-32-dll-instead-of-ws2-32-dll apply to your case? The accepted solution there claims -LC:\Windows\system32 <your files> ws2_32.dll works.

If that is not the issue. I would concentrate initially on the first error message, "multiple definition", and only look at the further errors after resolving that. I would write a tiny standalone program with #include <ws2tcpip.h> and a minimal socket connect() or similar and get that linking successfully. If that works you need to go look at the code you have using sockets, it might have e.g. MSVC-only #ifs which change the behaviour with a non-MSVC compiler that you need to address.

[pingal]

@JonB

Thank you. I have created a tiny standalone executable on QT which identified the problem, as i think the below line was pulling .lib file

LIBS += -LC:/Windows/System32 -lWs2_32

I've replaced it with the following and now the app compiled.

LIBS += -lws2_32

[JonB]

@pingal
That is a funny one! Windows should be case-insensitive, filename-wise. However, it looks like MinGW linker is case-sensitive to some degree.