Compiling libmodbus in Qt Creator on Windows throws undefined reference to '_imp_…' errors

Question

I have the source .h and .c files for libmodbus ( http://libmodbus.org/releases/libmodbus-3.0.6.tar.gz ). I dumped them into my Qt Project after learning that Qt is smart enough to know the difference b/wc and c++ files.

I include modbus.h in main.cpp and I get about 50 errors (most of which are undefined reference errors). Note I did get libmodbus working in ubuntu using codeblocks and it was communicating fine. I'm trying this in windows now and both Qt and codeblocks seem to be angry at me.

Here is my .pro file. QT += core QT += widgets

QT       -= gui

TARGET   = testModBus
CONFIG   += console
CONFIG   -= app_bundle

TEMPLATE = app

QMAKE_CXXFLAGS  += -w
QMAKE_CFLAGS    += -w


SOURCES += main.cpp \
modbus.c \
modbus-data.c \
modbus-rtu.c \
modbus-tcp.c

HEADERS += \
config.h \
modbus.h \
modbus-private.h \
modbus-rtu.h \
modbus-rtu-private.h \
modbus-tcp.h \
modbus-tcp-private.h \
modbus-version.h \
zModBus.h \
inttypes.h \
stdint.h

And here is my Qt Output when I try to Compile:

18:03:02: Starting: "E:\Qt\Tools\mingw48_32\bin\mingw32-make.exe" 
E:\Qt\5.2.1\mingw48_32\bin\qmake.exe -spec win32-g++ -o Makefile ..\testModBus\testModBus.pro
E:/Qt/Tools/mingw48_32/bin/mingw32-make -f Makefile.Release
mingw32-make[1]: Entering directory 'C:/Users/SSK/Desktop/qtProjects/build-testModBus-Desktop_Qt_5_2_1_MinGW_32bit-Release'
g++ -Wl,-s -Wl,-subsystem,console -mthreads -o release\testModBus.exe release/main.o release/modbus.o release/modbus-data.o release/modbus-rtu.o release/modbus-tcp.o  -lglu32 -lopengl32 -lgdi32 -luser32 -LE:\Qt\5.2.1\mingw48_32\lib -lQt5Widgets -lQt5Gui -lQt5Core 


release/modbus-tcp.o:modbus-tcp.c:(.text+0x24f): undefined reference to `_imp__select@20'
release/modbus-tcp.o:modbus-tcp.c:(.text+0x2a3): undefined reference to `_imp__recv@16'
release/modbus-tcp.o:modbus-tcp.c:(.text+0x2d7): undefined reference to `_imp__recv@16'
release/modbus-tcp.o:modbus-tcp.c:(.text+0x30d): undefined reference to `_imp__shutdown@8'
release/modbus-tcp.o:modbus-tcp.c:(.text+0x31c): undefined reference to `_imp__closesocket@4'

Makefile.Release:85: recipe for target 'release\testModBus.exe' failed
release/modbus-tcp.o:modbus-tcp.c:(.text+0x363): undefined reference to `_imp__setsockopt@20'
release/modbus-tcp.o:modbus-tcp.c:(.text+0x394): undefined reference to `_imp__ioctlsocket@12'
release/modbus-tcp.o:modbus-tcp.c:(.text+0x3c6): undefined reference to `_imp__connect@12'

mingw32-make[1]: Leaving directory 'C:/Users/SSK/Desktop/qtProjects/build-testModBus-Desktop_Qt_5_2_1_MinGW_32bit-Release'
makefile:34: recipe for target 'release' failed


release/modbus-tcp.o:modbus-tcp.c:(.text+0x3e2): undefined reference to `_imp__WSAGetLastError@0'
release/modbus-tcp.o:modbus-tcp.c:(.text+0x444): undefined reference to `_imp__select@20'
release/modbus-tcp.o:modbus-tcp.c:(.text+0x47f): undefined reference to `_imp__getsockopt@20'
release/modbus-tcp.o:modbus-tcp.c:(.text+0x517): undefined reference to `_imp__send@16'
release/modbus-tcp.o:modbus-tcp.c:(.text+0x597): undefined reference to `_imp__WSAStartup@8'
release/modbus-tcp.o:modbus-tcp.c:(.text+0x624): undefined reference to `_imp__socket@12'
release/modbus-tcp.o:modbus-tcp.c:(.text+0x65e): undefined reference to `_imp__htons@4'
release/modbus-tcp.o:modbus-tcp.c:(.text+0x66f): undefined reference to `_imp__inet_addr@4'
release/modbus-tcp.o:modbus-tcp.c:(.text+0x6c8): undefined reference to `_imp__closesocket@4'
release/modbus-tcp.o:modbus-tcp.c:(.text+0x74c): undefined reference to `_imp__getaddrinfo@16'
release/modbus-tcp.o:modbus-tcp.c:(.text+0x780): undefined reference to `_imp__socket@12'
release/modbus-tcp.o:modbus-tcp.c:(.text+0x7bb): undefined reference to `_imp__freeaddrinfo@4'
release/modbus-tcp.o:modbus-tcp.c:(.text+0x7d5): undefined reference to `_imp__closesocket@4'
release/modbus-tcp.o:modbus-tcp.c:(.text+0x82f): undefined reference to `gai_strerrorW'
release/modbus-tcp.o:modbus-tcp.c:(.text+0x8bc): undefined reference to `_imp__select@20'
release/modbus-tcp.o:modbus-tcp.c:(.text+0x96c): undefined reference to `_imp__socket@12'
release/modbus-tcp.o:modbus-tcp.c:(.text+0x9ab): undefined reference to `_imp__setsockopt@20'
release/modbus-tcp.o:modbus-tcp.c:(.text+0x9f0): undefined reference to `_imp__htons@4'
release/modbus-tcp.o:modbus-tcp.c:(.text+0xa0a): undefined reference to `_imp__inet_addr@4'
release/modbus-tcp.o:modbus-tcp.c:(.text+0xa2a): undefined reference to `_imp__bind@12'
release/modbus-tcp.o:modbus-tcp.c:(.text+0xa45): undefined reference to `_imp__listen@8'
release/modbus-tcp.o:modbus-tcp.c:(.text+0xa69): undefined reference to `_imp__htonl@4'
release/modbus-tcp.o:modbus-tcp.c:(.text+0xa85): undefined reference to `_imp__closesocket@4'
release/modbus-tcp.o:modbus-tcp.c:(.text+0xb38): undefined reference to `_imp__getaddrinfo@16'
release/modbus-tcp.o:modbus-tcp.c:(.text+0xb89): undefined reference to `_imp__setsockopt@20'
release/modbus-tcp.o:modbus-tcp.c:(.text+0xb99): undefined reference to `_imp__closesocket@4'
release/modbus-tcp.o:modbus-tcp.c:(.text+0xbc8): undefined reference to `_imp__socket@12'
release/modbus-tcp.o:modbus-tcp.c:(.text+0xbf9): undefined reference to `_imp__freeaddrinfo@4'
release/modbus-tcp.o:modbus-tcp.c:(.text+0xc23): undefined reference to `_imp__bind@12'
release/modbus-tcp.o:modbus-tcp.c:(.text+0xc33): undefined reference to `_imp__closesocket@4'
release/modbus-tcp.o:modbus-tcp.c:(.text+0xc63): undefined reference to `_imp__listen@8'
release/modbus-tcp.o:modbus-tcp.c:(.text+0xc77): undefined reference to `_imp__freeaddrinfo@4'
release/modbus-tcp.o:modbus-tcp.c:(.text+0xca5): undefined reference to `_imp__closesocket@4'
release/modbus-tcp.o:modbus-tcp.c:(.text+0xcda): undefined reference to `gai_strerrorW'
release/modbus-tcp.o:modbus-tcp.c:(.text+0xd61): undefined reference to `_imp__accept@12'
release/modbus-tcp.o:modbus-tcp.c:(.text+0xd8b): undefined reference to `_imp__inet_ntoa@4'
release/modbus-tcp.o:modbus-tcp.c:(.text+0xdc8): undefined reference to `_imp__closesocket@4'
release/modbus-tcp.o:modbus-tcp.c:(.text+0xe19): undefined reference to `_imp__accept@12'
release/modbus-tcp.o:modbus-tcp.c:(.text+0xe57): undefined reference to `_imp__closesocket@4'

e:/qt/tools/mingw48_32/bin/../lib/gcc/i686-w64-mingw32/4.8.0/../../../../i686-w64-mingw32/bin/ld.exe: release/modbus-tcp.o: bad reloc address 0x250 in section `.rdata'
e:/qt/tools/mingw48_32/bin/../lib/gcc/i686-w64-mingw32/4.8.0/../../../../i686-w64-mingw32/bin/ld.exe: final link failed: Invalid operation

collect2.exe: error: ld returned 1 exit status
mingw32-make[1]: *** [release\testModBus.exe] Error 1
mingw32-make: *** [release] Error 2
18:03:04: The process "E:\Qt\Tools\mingw48_32\bin\mingw32-make.exe" exited with code 2.

Answer 1

You need to include ws2_32.lib in your dependencies. Ie in your *.pro file add the line:

LIBS += -lws2_32

Answer 2

Turns out that the error was generated because of __declspec(dllexport) in one of the header files. Removed that and it went away. Then it started throwing a new error which is where I'm currently stuck at.