Coding when you are using an OS or library that requires a series of calls that build on each other to get the final result requires a set of checks to make sure each stage is successful. If some of the stages also require it partner call to free/close/destroy the items, then the programming logic requires you to be careful in how you tear down the items if there is an error in the middle of the process.
This can be coded several ways, and this post discusses a series of approaches in C++. The code selected for the example is performing Windows OS calls. These are done at the lowest API level without any other library or framework. The code has three places where tear down is required. The flow is complex enough to stop a simple reorganisation of the code to perform the same task. There is no addition error management present so make it easier to read. It is a fully working program and it gets a list of USB devices that the program is allowed access to.
Using the logic that we should use tools that are as simple as possible and only adopt complexity where it is absolutely necessary, it feels like I could use a very early version of C++. What follows are the reasons why I have increased that to C++17. The idea will be to only use these feature and no more. Any new use will be add to this page.
This is just to make sure I can reproduce the exact builds when using Visual Studio’s IDE. The settings tend to be in dialogue boxes that require manual changes. These instructions show where to find the key changes.
Two main sections. There is the IDE settings themselves and also the projects Configuration Properties. Note that debugging is in with the IDE and not with the compiler configuration.
Further down will be a discussion on how to update Visual Studio directly via its XML files.
And that is true of course. To go beyond that we have structures and classes which have explicit construction and operators. However, C++ has inherited C strings which are just a pointer to the first char, but they also have a long history where the construction and operations are well known. So, when a C String is given to a map or vector, it may be thought that it could be doing a deep copy. After all, it is known (by implicit rules) how this could be completed. The size is defined. It is just not stored. Also, the storage is clear – just not managed.
This started out as a task to learn simple class inheritance. To work out the syntax and idiomatic way to use them in C++. I just kept typing things that I thought would work and the compiler would slowly teach me what was wrong.
class rectangle : public shape
rectangle(float half) : shape(half)
This is a series of things that I found out when learning C++. The approach is going to be non-standard and likely to annoy any normal C++ professional. I am interested in languages in general and so I will be doing all my early code without STL at all. I want to learn what features the language offers before starting to use the standard libraries. To this end I try to do do simple version of the features that are already available. That way I can see how these features are implemented in the standard libraries. To me, that feels like a important advantage in learning a language. I did try to read the code for the libraries but it has a lot of very nuanced additions that I will only get to understand much later on. The code is still interesting to step through however as it does offer clues as to how to unpick various implementations.
In learning C++ I dug in and tried to use classes and templates to solve what feels like a typical use case. I found that what I needed was Template Specialisation and that C++ does not support this very well. I came up with 3 different methods and wanted to check what others though was we the best approach. If there was a “preferred idiom in C++”, or an even better solution.