Context: I'm using Qt 5.9.3 on Windows, building for MinGW 32-bit. The Qt part is a side issue though - the problem seems to be with MinGW. The version of MinGW is 4.3.0, supplied prebuilt as part of the Qt installation.
I'm building a library which talks to a USB device over HID. Everything compiles fine, but it fails at the link stage with
./..\..\object\debug\usb_hid_device.o: In function `ZN8MyApp3USB5Win3213getDevicePathB5cxx11Ell':
<MYPATH>/../../source/win32/usb_hid_device.cpp:99: undefined reference to `HidD_GetAttributes(void*, _HIDD_ATTRIBUTES*)#8'
./..\..\object\debug\usb_hid_device.o: In function `ZN8MyApp3USB5Win3214CHIDDeviceImplC2EllRNS_15LogPerComponentE':
<MYPATH>/../../source/win32/usb_hid_device.cpp:200: undefined reference to `HidD_FlushQueue(void*)#4'
The linker command is
g++ -shared -mthreads -Wl,-subsystem,windows -Wl,--out-implib,<MYPATH>\bin\debug\libusb_hid_comms.a -o <MYPATH>\bin\debug\usb_hid_comms.dll object_script.usb_hid_comms.Debug -lhid -lsetupapi -LC:\Qt\Qt5.9.3\5.9.3\mingw53_32\lib C:\Qt\Qt5.9.3\5.9.3\mingw53_32\lib\libQt5Guid.a C:\Qt\Qt5.9.3\5.9.3\mingw53_32\lib\libQt5Cored.a
If I omit -lhid I get the same errors. I also get the same errors if I remove -lhid and explicitly set the path and filename to libhid.a. If I deliberately mistype the path and filename, it comes up with an error, so I know the command-line is getting parsed correctly. But for whatever reason, MinGW appears to not be linking with one of its own library files.
I've also tried removing -lsetupapi and I get the linker errors I'd expect for the functions defined in there. Likewise the Qt library files. But it seems that specifically for libhid.a, MinGW can see the library file but just isn't going to link with it.
Has anyone else seen this? Or can anyone else with the same (or similar) version of MinGW confirm or deny that they can link with libhid.a? Or is there something obviously wrong with what I'm doing?
I've just found the answer. I'm posting an answer myself so that other people know in future, because I think this is still a valid question which people might want to know about.
The problem is the include file hidsdi.h. The majority of other header files which pull in Win32 API calls have extern "C" around the function declarations. However this one doesn't! The result is that we end up with C++ name mangling for linker symbols, instead of the C-style "_" in front of the linker symbols.
The solution is to use
extern "C"
{
#include <hidsdi.h>
}
and then everything works fine.
The version of hidsdi.h with the older version of MinGW (which I'm porting from) did have that protection around the function declarations. However it looks like it's gone in the newer version.
Related
I was trying to include the GMP library, which was simply the code below(I did nothing else):
#include <gmpxx.h>
However, when I tried to compile the code, the following error from g++ compiler occured:
myCode.cpp:3:10: fatal error: gmpxx.h: No such file or directory
#include <gmpxx.h>
^~~~~~~~~~~~~~~~~~~~~~
I have tried everything I searched online, putting the GMP lib here and there, adding INFINITE includepaths in c_cpp_properties.json, still, it keeps showing the message, although, I can find the file through "Go to Definition" option.
Is there any known solution to this?
It's not enough to configure VS Code includes, you need to pass those options to the compiler as well.
You don't mention your platform at all, so I'm going to use an example from my personal machine, a Macbook Pro with the fmt library.
When compiling with the fmt library, I have to provide three more options to the compiler.
-I/usr/local/include // Tells the compiler where to look for extra includes
-L/usr/local/lib // Tells the compiler where to look for extra libraries
-lfmt // fmt-specific command to use fmt library
So the full command ends up looking like this:
g++ -Wall -std=c++17 -I/user/local/include -L/usr/local/lib -lfmt main.cpp
I need all three options because fmt is installed in a non-standard location that the compiler doesn't check by default. According to the documentation, you can get away with just -lgmp and -lgmpxx if you installed the library in a standard location (happens by default with *nix and a package manager, I imagine).
If you use build tasks in VS Code, this can be set up and automated for you.
Sort briefing what I am trying to do:
I want to use vnode-lp on my windows PC. I’ve installed MinGW. I’ve installed the necessary dependencies like LAPACK & BLAS libraries as well as Profil/BIAS. The installation of all libraries passed the make and make install process without errors. I hope (!) I’ve managed to install it correctly.
Now the Problem:
Now I’ve tried to get a simple program compiled with basically northing in it just an #include “vnode.h”. First I tried it with Microsoft Visual Studio. Since this gave me several errors I tried to compile it with g++ using MinGW. This gives me the same errors. It starts with
./matrix.w:90:17: error: ‘v_bias’ is not a namespace-name
The Question:
How to include vnodelp into an c++ program and compile it without errors under windows, am I missing something?
Off-topic:
I am trying to get this running for over a week now and don’t know what to do anymore.
C++ is most definitely not C, and packages designed for C++ will never compile and run as C code. So, what you're trying to do really can't be done unless you do some fancy stuff by creating a .dll or something like that, and even then I think you wouldn't get the functionality you want. Why not write your code in C++ and compile with g++ or a similar compiler?
I have managed to finally solve this issue. In case someone has the same problem here is the solution.
I have missed something in the call. Here is the full call that has worked for me:
g++ -o2 –Wall –Wno-deprecated –DNDEBUG – DPROFIL_VNODE – DMAXORDER=50 –I(path to profil bias)/include –I(path to profil bias)/include/BIAS –I(path to profil bias)/src/Base –I(path to vnodelp)/FADBAD++ -I../include –DNDEBUG –c –o (filename).o (filename).cc
g++ -L(path to profil bias)/lib –L(path to lapack)/lib –L../lib –o (filename) (filename).o –lvnode –lProfil –lBias –llr (path to lapack)/lib/liblapack.lib (path to lapack)/lib/libblas.lib –lstd++
funfact:
This also complies with gcc instead of g++
I am trying to work through this tutorial on OpenCL, on a Windows 10 dev system which has integrated Intel HD graphics. I have installed Intel's OpenCL SDK. I have added the include directory from the SDK install into Properties > C/C++ General > Paths and Symbols > Includes. I am using MinGW as my compiler for Eclipse
In response to a number of linker errors that popped up when I first tried to compile the project, I set up the linker in eclipse to point to opencl.lib as outlined in this answer.
That took care of the linker errors, but there's an offending line from the tutorial which makes it impossible for the tutorial boiler-plate to compile:
87 cl_int result = program.build({ device }, "");
Set up as I am, this gives me the following warning and error:
..\src\main.cpp:93:32: warning: extended initializer lists only available with -std=c++11 or -std=gnu++11
..\src\main.cpp:93:45: error: no matching function for call to 'cl::Program::build(<brace-enclosed initializer list>, const char [1])'
If I'm reading this correctly (I haven't used C++ since before C++11 was a thing), the compiler is first warning me that it doesn't properly recognize what {device} is supposed to be (a vector of devices which has only one entry in it, initialized earlier in the code). Then, since it doesn't recognize {device}, the compiler errors out because it can't find a signature for cl::Program::build with arguments that match whatever-the-heck it's interpreting {device} to be.
Following the warning's advice, I followed the instructions given in this answer to add the -std=c++11 option for the compiler. However, when I do that the linker errors come back. Trying to compile with these options results in about thirty errors which all basically say they can't find any reference for the CL calls in the library files. For example:
C:/Program Files (x86)/Intel/OpenCL SDK/6.3/include/CL/cl.hpp:1753: undefined reference to `clGetPlatformInfo#20'
How do I make the compiler behave? I think I remember reading somewhere that the order of compiler options in the command line matters withe regards to linking, could that be messing up my compile since I added the -std=c++11 option?
I (sort of) figured out why the compiler was unhappy--the library I was linking was the x64 library for OpenCL installed in [base Intel dir]\OpenCL SDK\6.3\lib\x64, but (I think?) my compiler is not set up to create x64 apps. When I link to the .lib file in OpenCL SDK\6.3\lib\x86 my linker errors disappeared.
The actual error is a linker error. Undefined reference to get_driver_instance.
Any ideas what the problem is?
This is what I did to install.
Download and install MinGW to C:\MinGW. http://www.mingw.org/
Download boost and move the boost folder to C:\MinGW\include
Download Connector/C++ 1.1.3 http://dev.mysql.com/downloads/connector/cpp/
Move the mysql_connector/include/*.h (recursively) to C:\MinGW\include\
Move the mysql_connector/lib/mysqlcppconn-static.lib to C:\MinGW\lib\libmysqlcppconn-static.a
Move the mysql_connector/lib/mysqlconncpp.dll to C:\MinGW\lib\mysqlconncpp.dll
Alter cppconn/config.h to remove dupication
Copy the C++ example and name it test.cpp http://dev.mysql.com/doc/refman/5.1/en/connector-cpp-examples-complete-example-1.html
add "using namespace sql::mysql" to the file (as recommended)
run "g++ test.cpp -L C:\MinGW\lib -l mysqlcppconn-static"
It's likely in a namespace.
throw in this and see what happens:
using namespace sql::mysql;
edit: Also, did you look through the approximately 869 other times people have asked this same question on stack overflow before posting?
https://www.google.com/search?q=mysql+get_driver_instance+site:stackoverflow.com
If that isn't it, it can be a problem with c++ name mangling.
https://en.wikipedia.org/wiki/Name_mangling#Name_mangling_in_C.2B.2B
Because the name-mangling systems for such features are not standardized across compilers, few linkers can link object code that was produced by different compilers.
and I think the final answer is here:
http://www.mingw.org/wiki/MixingCompilers
another stack overflow answer saying this:
What problems can appear when using G++ compiled DLL (plugin) in VC++ compiled application?
You'll need to build the connector from source using your g++ compiler:
http://dev.mysql.com/doc/refman/5.1/en/connector-cpp-installation-source.html
I am getting undefined reference to 'mysql_suchandsuch##' messages when trying to link my program with the MySQL libraries supplied with the 5.5 server. When MySQL was installed, I used the default path, which for me on Windows is C:\Program Files\MySQL\MySQL Server 5.5\. Originally, I had thought that the spaces are causing my grief, but I think I've correctly worked out how to point to the library path without spaces (still with no luck). If there's another probable cause, please let me know.
I have reviewed a series of questions on this site trying to resolve my issue...
Question 1
Question 2
Question 3
Question 4
Question 5
Question 6
Question 7
Using mingw/g++, I have tried to link using the following options, based on my own research as well as suggestions here:
-L"C:\Program Files\MySQL\MySQL Server 5.5\lib\" -llibmysql.lib
-L"C:\Program Files\MySQL\MySQL Server 5.5\lib\" -lmysqlclient.lib
-L"C:\Progra~1\MySQL\MySQLS~1.5\lib\" -llibmysql.lib
-LC:\Progra~1\MySQL\MySQLS~1.5\lib\ -lmysqlclient.lib
-L"C:\Progra~1\MySQL\MySQLS~1.5\lib\" -lmysql
In all cases, I have put the -L/-l options at the right-most part of the statement, as I understand this can matter.
I have confirmed the libraries do exist. In the /lib dir, I have libmysql.lib, mysqlclient.lib, and libmysql.dll. I have not tried to link with the .dll, as no tutorial/forum I've reviewed suggested that.
I am not using MAKEFILES.
Does anyone have specific experience with g++/MySQL?
The following commands work fine for me using a GCC 4.6.1 from November 2011:
g++ my.cpp -I D:\Opt\MySQL5.5\include ^
D:\Opt\MySQL5.5\lib\libmysql.dll -o myWithDll.exe
g++ my.cpp -I D:\Opt\MySQL5.5\include ^
-L D:\Opt\MySQL5.5\lib -lmysql -o myWithLib.exe
So both linking against the LIB and the DLL do work.
You may get a warning (see Gaffi's comment). This is because the linker does fuzzy linking for you without you having it specified; normally, it would have failed to link. It is being nice, though, and making it work for you, at the same time warning you about things happening without your having requested them. The way to suppress the warning is to make fuzzy linking explicit:
g++ -Wl,--enable-stdcall-fixup my.cpp -I D:\Opt\MySQL5.5\include ^
D:\Opt\MySQL5.5\lib\libmysql.dll -o myWithDll.exe
g++ -Wl,--enable-stdcall-fixup my.cpp -I D:\Opt\MySQL5.5\include ^
-L D:\Opt\MySQL5.5\lib -lmysql -o myWithLib.exe
This is a Cygwin/RedHat/MinGW extension to the linker; the docs are here:
--enable-stdcall-fixup
--disable-stdcall-fixup
If the link[er] finds a symbol that it cannot resolve, it will attempt to
do “fuzzy linking” by looking for another defined symbol that differs
only in the format of the symbol name (cdecl vs stdcall) and will
resolve that symbol by linking to the match. For example, the
undefined symbol _foo might be linked to the function _foo#12, or the
undefined symbol _bar#16 might be linked to the function _bar. When
the linker does this, it prints a warning, since it normally should
have failed to link, but sometimes import libraries generated from
third-party dlls may need this feature to be usable. If you specify
--enable-stdcall-fixup, this feature is fully enabled and warnings
are not printed. If you specify --disable-stdcall-fixup, this feature is
disabled and such mismatches are considered to be errors. [This option
is specific to the i386 PE targeted port of the linker]
did you try -lmysql as the linker automatically prepends lib and appends .lib