Support Note Question  How do I compile a CANLIB program using gcc (cygwin or MinGW) in Windows? Answer You should be able to use the Microsoft version of the canlib32 import library. Here's an example when compiling using gcc from cygwin: c:\program files\kvaser\canlib\samples\candemo>which gcc gcc is an external : C:\cygwin\bin\gcc.exe c:\program files\kvaser\canlib\samples\candemo>gcc --version gcc (GCC) 3.4.4 (cygming special) (gdc 0.12, using dmd 0.125) Copyright (C) 2004 Free Software Foundation, Inc. This is free software; see the source for copying conditions.  There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. c:\program files\kvaser\canlib\samples\candemo>gcc -o candump_cygwin -I..\..\inc candemo.cpp -L..\..\lib\ms -lcanlib32 candemo.cpp: In function `void InitDriver()': candemo.cpp:158: warning: passing NULL used for non-pointer converting 4 of `canStatus canIoCtl(int, unsigned int, void*, unsigned int)' candemo.cpp:166: warning: converting of negative value `-0x000000001' to `unsigned int' candemo.cpp:169: warning: converting of negative value `-0x000000002' to `unsigned int' candemo.cpp:172: warning: converting of negative value `-0x000000003' to `unsigned int' candemo.cpp:175: warning: converting of negative value `-0x000000004' to `unsigned int' candemo.cpp:178: warning: converting of negative value `-0x000000005' to `unsigned int' candemo.cpp:181: warning: converting of negative value `-0x000000006' to `unsigned int' candemo.cpp:184: warning: converting of negative value `-0x000000007' to `unsigned int' candemo.cpp:187: warning: converting of negative value `-0x000000004' to `unsigned int' candemo.cpp: In function `int main(int, char**)': candemo.cpp:468: warning: passing NULL used for non-pointer converting 4 of `canStatus canIoCtl(int, unsigned int, void*, unsigned int)' candemo.cpp:674: warning: converting to non-pointer type `int' from NULL c:\program files\kvaser\canlib\samples\candemo>   Q: Why doesn't the following work? c:\program files\kvaser\canlib\samples\simple> gcc –o simple_cygwin –L../../lib/ms –lcanlib32 simple.o simple.o:simple.c:(.text+0xd4): undefined reference to `_canGetErrorText@12' This problem has to do with the way gcc handles arguments for the linker (object files and libraries). Unlike other arguments, they are order-dependent. Here's an excerpt from the gcc online manual: (http://gcc.gnu.org/onlinedocs/gcc/Link-Options.html#Link-Options) |-l |library    Search the library named library when linking. (The second    alternative with the library as a separate argument is only for    POSIX compliance and is not recommended.)    It makes a difference where in the command you write this option;    the linker searches and processes libraries and object files in the    order they are specified. Thus, `foo.o -lz bar.o' searches library    `z' after file foo.o but before bar.o. If bar.o refers to functions    in `z', those functions may not be loaded. ... As you can see, you need to put the "-lcanlib32" after "simple.o" for everything should work as you expect.