I want to embed python code in C++ console application vs2015. I followed the tutorial https://docs.python.org/3/extending/embedding.html, the very first example, 5.1 Very High Level Embedding. But when I built (in release mode) it shows an error: unresolved external symbol ___imp__py_initialize.
I guess error occurred cause I don't Include some .lib or .obj files, so I include python.h and python.lib but I'm not sure.
(I'm not good in English, so excuse me ...)
If you are sure that you have set the input and library directories correctly, then the cause of the linker problem might be that you are mixing codes of different bitnesses. Make sure that for example, you are not linking against the 64-bit versions of the Python libs in a 32-bit application.
"unresolved external symbol" is a linker error that means you forgot to link to a .lib file.
The Visual C++ project settings you need to embed Python are (for example Python 3.5):
C/C++, General, Additional include directories: C:\Python35\include
Linker, General, Additional library directories: C:\Python35\libs
You don't need to manually specify the .lib file because pyconfig.h auto-links to it when included.
Related
I'm trying to create a native HoloLens 2 C++ application with OpenXR. In the Microsoft OpenXR-MixedReality example I discovered the XrSceneLib_uwp project which has the configuration type set as static library (.lib) in the Visual Studio properties. Accordingly to that I tried to add it as a library in my solution which also has a Core Application (C++/WinRT) in it where I want to use the functions from XrSceneLib_uwp. In my thinking it makes sens because I can use the library for example to create a holographic title scene without much effort. The problem here is that when I build my solution I'm getting linker errors and I don't know how to fix them. I'm also relatively new to Visual Studio (22 in my case) and most likely I'm just doing someting wrong in the linking process.
Linker error when I try to build:
Error LNK2019 unresolved external symbol xrGetInstanceProcAddr referenced in function "public: __cdecl `anonymous namespace'::ImplementXrApp::ImplementXrApp(struct engine::XrAppConfiguration)" (??0ImplementXrApp#?A0x934f03db##QEAA#UXrAppConfiguration#engine###Z) CoreApp3 \repos\CoreApp3\CoreApp3\XrSceneLib_uwp.lib(XrApp.obj) 1
My solution explorer
Here is what I do:
I copy and paste the shared and openxr_preview folders from the OpenXR-MixedReality .zip file in my project folder.
Add XrSceneLib_uwp.vcxproj in /shared/XrSceneLib as an existing project to my solution.
Add the path to the copied shared and openxr_preview folders in Properties->Configuration Properties->C/C++->General->Additional Include Directories.
Add also the path to XrSceneLib_uwp.vcxproj in Additional Include Directories in my main project (CoreApp).
Add reference in CoreApp to XrSceneLib_uwp (Add->Reference->Projects).
After that everything works fine and I can even build the solution. But when I try to use the library I'm getting these linker errors. I don't understand why it works in the OpenXR-MixedReality examples but not when I try to implement it on an different project. What am I missing? I assume that XrSceneLib may not have been designed to be used externally in other projects but at the same time I think it should be possible somehow.
I also tried to add Additional Library Directories and the missing object files but either I have done something wrong or it just simply does not work.
I really appreciate any help.
I think the linker is failing to find the OpenXR Loader. The sample projects in the microsoft/OpenXR-MixedReality github repo link to the OpenXR Loader using the NuGet package manager. I get the same linker error if I purposely remove the NuGet package references from the sample projects.
You can either link to the OpenXR Loader using NuGet or you can build the OpenXR Loader youself. Take a look at the "Using OpenXR in an existing project" section on the microsoft site:
https://learn.microsoft.com/en-us/windows/mixed-reality/develop/native/openxr-getting-started#using-openxr-in-an-existing-project
I'm using the <XZY> IDE to compile my program, and have some trouble to import/integrate a specific library with it.
I get error messages like
fatal error: 3rdPartyLib.h: No such file or directory
for a
#include "3rdPartyLib.h"
statement
ld.exe: cannot find `lib3rdParty.a`
for specifying
3rdParty
in the additional libraries
At least I got some error message like
undefined reference to `lib3rdParty::foo()'
What can I do to fix this?
It's a common misconception, that the current IDE used, is responsible for getting errors like stated in the question.
See for example
c++ lib in two same project ,one can work but the other can 't
Issue linking libxml++ and glib libraries with CodeBlocks IDE for C++ Windows
...
The problem is almost never related to the currently used IDE.
In the most cases the solution boils down, to supply the actual toolchain's compiler/linker with the appropriate path's to search for included headers, to be linked libraries.
One of the major applicable answers for the linker related problems are
What is an undefined reference/unresolved external symbol error and how do I fix it?
undefined reference to `WinMain#16'
Most of the common IDEs provide features to configure this for a specific project. Here are some samples
Eclipse-CDT
Include path settings:
Library & library search path settings
Visual Studio 2013
Code Blocks
**DEV C++ (Bloodshed C++)
As from their FAQ:
9. How can i use the OpenGL library and others ?
All the libraries that comes with Mingw reside in the Lib directory. They are all named in the following way: lib*.a
To link a library with your project, just add in Project options, Further option files :
-lopengl32
This is for including the libopengl32.a library. To add any other library, just follow the same syntax:
Type -l (L in lowercase) plus the base name of the library (filename without lib and the .a extension).
You may also consider putting a -L option there to add directory pathes searched for libraries.
Qt Creator
In order to add include paths you have to open up the .pro file and then add
the directories to the INCLUDEPATH variable. These paths are separated by spaces. Reference can be found here.
If none of the above samples applies for your actually used IDE/toolchain, I hope you're able to get the point of abstraction:
It's an issue how to provide compiling/linking options to your actual toolchain. The IDE used to setup the context is a minor point here.
For eclipse I use the pkg-config plugin where possible:
https://marketplace.eclipse.org/content/pkg-config-support-eclipse-cdt
Failing that this configuration window:
Using netbeans 7.2 and the most recent version of MinGW (using installer) I can't use the libnoise library. I am properly including the header files, the auto completion confirms this, however the library is simply not working. There is a .lib file and a .dll. I have tried every possible combination of adding them under project > properties > Build > Linker as well as putting the .dll in the base project directory. Despite all this I am still getting undefined reference errors whenever I try and run the code. Does anyone know what to do?
I know that it is possible to link import library files (*.lib) with MinGW, but I still suggest to recompile libnoise.
With the current Makefile, this is not very easy and may break. Thus I've written a CMake script, which doesn't only work on Windows, but should work on all CMake supported platforms. In addition to this, I've cleaned up the directory structure. The code itself hasn't been touched and when you build a library it should essentially be the same as the current one.
libnoise on GitHub
After you've built your shared library, you'll have a libnoise.dll.a and libnoise.dll file. You then add libnoise.dll.a to the linking settings and put the DLL itself next to the binary, or in the working directory.
You have to link the lib file (= adding it to linker libraries) and put the dll to
<project root>/dist/<...>/
(where your exe is put to). There's no need to add the dll to linker too.
Can you please post the error message you get?
I have a problem using boost.asio. I use Windows XP and Visual Studio 2005
I followed these steps:
I downloaded the latest version (http://sourceforge.net/projects/boost/files/boost/1.46.1/) of W: \boost_1_46_1
I set the environment variable INCLUDE : W:\boost_1_46_1
In the properties of my project (VS->tools->Options project&solutions->vcc++directories) I added $(INCLUDE)
I added in my file. h this:
I get the following error:
LINK : fatal error LNK1104: cannot open file 'libboost_system-vc80-mt-gd-1_46_1.lib
This is a linker error. Find the lib, and go to linker input, and add it there. Be sure to set the libpath as well. This picture should guide you:
The boost::asio library needs to be built. ( Many other boost 'libraries are headers only and do not need to be built ). Building it yourself is a small challenge. Better to use the pre-built binary installer which is here
Once you have the built libraries, one way or another, you have to tell the linker where they are. However, you do not need to specify each individual library by name, just specify the folder that contains them. The easiest way to do this IMHO is to create an environment variable called BOOSTROOT which you you set equal to the folder where you installed boost. Then you tell the linker to look for libraries in $(BOOSTROOT)/lib
We have a large project using VS2008 and boost 1_42. I'm trying to upgrade to VS2010 and boost 1_44. I installed VS2010 and boost 1_44 and converted the project. Now I am trying to build, and everything compiles, but fails when linking:
LINK : fatal error LNK1104: cannot open file 'libboost_thread-vc90-mt-1_42.lib'
I have changed the include and lib directories to point to the new boost 1_44 files and I have renamed the old boost 1_42 directory.
Why is the linker still looking for a vc90-1_42 file, when it is only using 1_44 headers? Is there a way that I can determine WHY the linker wants this file? The linker obviously thinks it needs the file, but why?
I have cleaned the project and I am re-building to ensure any old build files are erased.
I've run into exactly this problem a couple of times too. It's usually been some old temporary files but like in your case cleaning didn't always do the trick straight away. Does your project include any static libs that might have been built with 1.42?
Something you can try which may or may not be helpful in tracking down your issue:
Rename the old boost directory back to it's original name
Clean the solution
Under C/C++->Command Line->Additional Options add "/showIncludes"
Under Linker->Command Line->Additional Options add "/verbose:lib"
Rebuild all
Then when you build you'll be able to see at which point 1.42 headers are included, etc. in the output window. Somehow doing this helped me in tracking down where the problem was.
Along with changing the lib directory, you need to change the name of the boost library. That's in the Linker | Input section of the project settings.
Your added comment makes it clear that the dependency on the Boost 1.42 library was being created indirectly by another library that hadn't been rebuilt.
For this you basically have two choices: either add that library as a project to your main solution, and make sure it has enough dependency information that it'll be re-built when you upgrade Boost, or use the /Zl compiler switch when you build your library. This tells the compiler you're building a library so you do not want to embed library dependencies like this.
Boost uses
#pragma comment(lib)
command to inform the linker of libraries it needs to link with. It is not an error. If Boost says you need it, it's likely you do.
On How can I find out why the linker wants this file?
There are programs which will go through your app and dlls/libs and report the content of manifests and what the binaries report they depend on. You could then scan the report for the unexpected libraries being included. We used this mainly to find libs including the previous version of the VC runtime.
Have not used the one we had in about 5 years though, now if only I could remember the name of the app!
DependancyWalker (depends.exe) will allow you to see dependancies of dll/exe but not static libs.
You could open each binary as a 'file' in MSVS and look at the manifest content by hand, but I imaging this would be a bit painful. I've not tried this with a static lib.