I am learning C++ and, in order to do so, am writing a sample wxWidgets application.
However, none of the documentation I can find on the wxWidgets website tell me what library names to pass to the linker.
Now, apart from wxWidgets, is there a general rule of thumb or some other convention by which I should/would know, for any library, what the names of the object files are against which I am linking?
We have more of a "rule of ring finger", instead of a thumb
Generally, if you compile the library by hand, it will produce several library files (usually .a .lib or something similar, depending entirely on your compiler and your ./configure) these are produced (typically) because of a makefile's build script.
Now a makefile can be edited in any way the developer pleases, but there are some good conventions (there is, in fact, a standard) many follow- and there are tools to auto generate the make files for the library (see automake)
Makefiles are usually consistent
You can simply use the makefile to generate the files, and if it's compliant, the files will be placed in a particular folder (the lib folder I believe?) all queued up and ready to use!
Keep in mind, a library file is simply the implementation of your code in precompiled format, you could create a library yourself from your code quite easily using the ar tool. Because it is code, just like any other code, you don't necessarily want to include all of the library files for a given library. For instance with wxWidgets if you're not using rich text, you certainly don't want to waste the extra space in your end executable by including that library file. Later if you want to use it, you can add it to your project (just like adding a .cpp file)
Oh and also with wxWidgets, in their (fantastic) documentation, each module will say what header you need to include, and what library it is a part of.
Happiness
Libraries are amazing, magical, unicorns of happiness. Just try not to get too frustrated with them and they'll prance in the field of your imagination for the rest of your programming career!
After a bit more Googling, I found a page on the wxWidgets wiki which relates to the Code::Blocks IDE, but which also works for me. By adding the following to the linker options, it picks up all the necessary files to link:
`wx-config --libs`
(So that does not solve my "general rule" problem; for any library I am working with, I still have to find out what files to link against, but at least this solves the problem for wxWidgets).
The build instructions are different for each platform and so you need to refer to the platform-specific files such as docs/gtk/install.txt (which mentions wx-config) or docs/msw/install.txt to find them.
FWIW wxWidgets project would also definitely gratefully accept any patches to the main manual improving the organization of the docs.
Related
How can I use a library such as the GMP library in C++ in such a manner that the file can be compiled normally without having the person compiling to install the GMP themselves. This is for personal use(so no license issues etc.). I just want my client to be able to compile my C++ code which needs the GMP library. I tried using g++ -E option, and it kinda works, but the problem is that on top of it are included many files which are themselves part of the library(and not available without the lbrary). Also the linker needs the availability of the library even if I do do that successfully.
How do I copy the entire library per se, maintaining a single file of code, such that it compiles and doesn't cause problems. I'm quite sure it is doable, because copying some functions works like a charm, but I can't copy paste the 3000 line code manually, so how to do it?
If I understand you correctly, I guess what you want is to have your source and the entire GMP library in one file? And you want to do that automated?
I think there is no standard way to do this. You could write a script in you favorite language (bash, python, etc) which traverses the GMP code tree, appending the files (first the header files, then the cpp files) to your file while ignoring all local #include-lines. And hope that there are not too many macros etc which rely on the folder structure to be intact.
However, you could (and probably should) just supply the library and a adequate Makefile with your source code. Then the client wouldn't need to install the GMP lib, but could unpack the archive and run make. If the constraint is to do this in one file, maybe it is wiser to change that constraint...
I'm new to C++ and wonder if it is good practice to include a library by source code. If it is, what would be the best way to achieve this? Just copying in a subfolder and using include?
In my special case, I have written a small library and I'm going to use it on two different microprocessors. Compiling the library separately, copying all headers and using this "package" seems to be overkill for me.
Compiling the library separately is what should be done.
It's not that overkill either : you're just compiling the .o files for your library, then wrapping them in an archive and handling that archive around.
Normally libraries are used as libraries because it is much easier and comfortable that way. If you are using dynamic libraries (.dll or .so) things get even better because you can replace libraries on the fly and things should continue to work smoothly.
You decided to use code repositories instead of libraries which means probably more work for you. If you are happy this way that's OK, but just make sure you do not break any license, some lgpl packages (like Qt) clearly
require their libraries to be linked dynamically.
The best way to do this: hard to say but in your place I would probably use git and include the libraries as submodules.
Just #includeing source code is a bad idea since it means just to copy the code into your own, things can go wrong that way. For example if there is a static variable somewhere in the library code and the same named static variable in your code you will have a conflict.
Instead you should probably compile the library separately and link it, possibly the same way as you would do anyway (ie you build the library and then you link with that library). But the light weight alternative would be just to compile the additional C++ files and then link the object files together to an executable. Details on how you do that is compiler specific.
There's valid reasons for including the library source in this way, for example if your project needs to modify the library during development it would be easier to do so if the rebuilding of the library is done as a part of the build process of the project. With a well designed build process the library shouldn't have to be rebuilt unless there are actual changes to it.
The value of a library is in part that you link it more often than you compile it, leading to a net saving.
If you control all the source, then whatever build process works best for you is fine.
I agree with πάντα ῥεῖ but I'll also add that the reason it is bad practice is because the compiled library can be stored in your computer in a common location and used by tons of different programs, thereby reducing the amount of data your computer has to store, in memory as well as RAM(if more than one running program uses the same library). An example is openGL which is a library that many games use and is probably already in your system somewhere. If you use windows, software installers link up these libraries to their programs and add them if you don't have them. If you use linux, you will be notified if libraries are missing and prompted to install them. All of that aside, you can, technically use un-compiled libraries but that introduces a number of potential licensing problems as well as additional problems with THEIR dependencies.
By copying source code to other projects and "mixing" it with other source code will stop this library from being a "library". Later on you will be tempted to make a small change in one copy (for CPU) or fix a bug and forget to do the same in the other copy.
There might be additional consideration but you should try to keep the code in one place. Do not Repeat Yourself (DRY) is a very strong and fundamental principal of software engineering with many benefits.
I'm sorta new to C++ and I've decided to try and use odeint to do some simulations because python is too slow for my needs.
I found this package, which I want to play with. I'm just not totally sure how to install or where to place these libraries. Is there something for C++ similar to python's pip install?
Side note: I'm trying to do this using Eclipse Kepler, but I'm not married to that idea.
I recommend not putting the code into your own project - that is a rather quick and dirty solution. The correct way to use a library in C++ (in fact, in any programming language that I know) is to keep all libraries separate from your own projects, at a separate location on your filesystem.
You then tell your environment where to find the library files and tell your project to use them. It's always the same basic idea, whether you are using Makefiles or Visual Studio project files.
Look at the documentation of this library. It says:
odeint is a header-only library, no linking against pre-compiled code
is required
This means that the "library files" I just mentioned are just header files. That makes it much easier for you, because you don't have to deal with linker options. In C++, the location where additional (project-external) header files can be found is usually called the "include path".
Your new problem should therefore be: How to tell Eclipse Kepler my include path?
Entering this new problem into Google (as "eclipse kepler include path") yields a few interesting results. It will eventually lead you to the Eclipse documentation about include paths, where you can learn how to edit the C++ include path.
Now that everything is set up, you can finally use the library's header files in your projects via lines like the following:
#include <boost/numeric/odeint.hpp>
Do you notice the < >? They make a big difference, because they are the C++ way of saying "this is not part of my project, please get it from my include path". Just like headers which are part of the language (e.g. <vector> or <iostream>).
All of this may appear troublesome at first, and perhaps you even gain little from it at the beginning, but in the long run, for many different projects and many different libraries, it's the only way to prevent chaos.
Since odeint is a header only library you can place it with your own source code. Simply copy odeint's boost directory where your main.cpp is (assuming you have a main.cpp, but you should get the idea):
your_sources/
main.cpp
boost/
numeric/
odeint/
odeint.hpp
Now you can use the library by including
#include "boost/numeric/odeint.hpp"
A bit of a simple question, though the answer may not be. I am fairly new to C++ and was wondering if it was possible to open a C++ library and see it's code. It sounds like a potentially risky move to accidentally change the core code of the library, but I would still like to see if it is possible. Thank you!
There are too kinds of libraries that C++ can use:
compiled to binary libraries which are linked with linker to your
executable;
headers-only libraries which are just included with include into
your source code
You can "open" headers of headers-only libraries and modify code if you wish (but not recommended).
Also many compiled libraries are open source. You can open source files there. If you want to modify such library, you will need to compile it and link your executable against this modified version.
Yes it s possible to open a c++ library and see its code.
If you want to make changes to any functionality simply create your own version of it giving it a different name, or if you want to add functionality just simply extend the class you are interested in. (read up on inheritance for this).
I'm totally spinning my wheels with getting a couple of 3rd party libraries to work with my c++ programs. I'm looking for some general advice (40,000 foot level) about the general steps that one needs to take when implementing libraries.
First, some specifics: I am using code::blocks in Windows as my IDE. I like this IDE and really don't want to switch to anything else if I don't have to (I've tried visual c++ and also some things in linux). The libraries that I am trying to use are GMP and crypto++.
OK. What I think I know is this: After downloading the library, I unzip the file to a folder. I've been unzipping directly to C:\ with each zip file extracted to its own folder (e.g. c:\cryptopp and c:\gmp). I think that the next step is to build the library, but this is where I get totally stuck. How is this done? There are no executable files among those extracted. From what I can tell, I believe that I do this in code::blocks, but I have no idea how?
Finally, assuming that I can get this done, which I believe creates the .lib files, the last step before actually using the library in my code, is to link into the library. This part, I believe that I understand.
So, my question is broad: do I understand this process overall? And if so, how do I go about building these libraries, if in fact that it the thing that I am missing.
Thanks very much for indulging my ignorance. I'm totally rudderless right now and despite hours and hours on google, I'm making no progress. Also, feel free to correct anything that I have stated as fact that is not correct. Thanks a lot!
Usually libraries have a special file called makefile in them, and are built with a utility called Make (or one of it's variations, whatever works uder windows).
Usually all you have to do is to run Make in the directory where you have unpacked the source files, and it will do the rest itself.
If those libraries you mention (GMP and crypto++; disclaimer: I'm not familiar with either of them) don't have project files for code::blocks then you may still be able to compile them under Windows with MinGW.
If you have installed MinGW you use the MinGW shell to navigate to the appropriate directories which would be /c/cryptopp/ and /c/gmp in your examples - The MinGW shell works like a Unix shell, and has different naming conventions.
Then you need to compile the libraries. Check whether there's a Makefile in those directories, if there isn't you can check whether there's a configure script, which will generate the Makefile. If you have the Makefile you can type make which will compile the libraries with MinGW's port of the GCC compiler.
When the compilation is complete you should have a library in the form of a .a file (say libcryptopp.a) that you can link to your project. In code::blocks you would set the linker path (the -L command line option in GCC) to C:\cryptopp\bin or wherever the library has been compiled, and then add libcryptopp.a to the list of libraries you want to link (this is associated with the -l option in GCC). The convention is to leave out the lib prefix and the .a extension, so you would just add cryptopp to your library list. In the end your linker options should look like -LC:\cryptopp\bin -lcryptopp along with the
Also, to be able to use the libraries you need to add the path to the headers directory to the include path of your project. This is associated to the -I command line option in GCC, so your compiler's command line options would have something like -IC:\cryptopp\include somewhere.
Of course, all of the above assumes that you use code::blocks with GCC. If you're using it with VisualC++ then the principles are the same, but the specific steps differ.