How I found interesting things about C and C++ languages while learning Symbian C++

It is interesting to see that while reading Symbian C++ code you discover things related to C or C++ language that are not quite the same as you already knew them.
Due to the limitations that a smart-phone has (mostly in terms of power consumption which, from a software perspective, translates into number of CPU cycles required to do something, and in terms of memory size), its corresponding software has to tackle in a very accurate manner some aspects which could be neglected by a PC desktop programmer.

I remember that while browsing a Symbian documentation I read somewhere that:


C++ introduces a memory overhead compared to C (a program compiled in C++ will be bigger than one compiled in C), so if you decide for writing an operating system in C++ you have to be more careful than when writing in C.

One thing which kept my attention when having first contact with Symbian was the fact that you should always use the appropriate data types. This was not very surprising for me taking into account that I have an embedded programming background and I know that I have to be very careful when using unsigned int and when int.
But this is not everything. Symbian even has dedicated typedef’ed data types for each C built-in type (except char and void), and it is strongly recommended to use those instead of C types.

While looking at some examples in Symbian C++ other strange things, like inline constructors, private copy-constructors, private static methods, overloading the new operator with new(ELeave), macros like TRAP and TRAPD, popped into my attention and revealed hidden aspects of C++ language.

Generally if you know C++ it would be quite simple to start writing software for Symbian smartphones. But if this is true, why I read everywhere about the steep Symbian learning curve?

Descriptors – a milestone in the Symbian C++ learning curve?

I guess many C enthusiast programmers wanting to switch to Symbian code developing, faced some issues when learning about Symbian descriptors. Even if many useful and helpful resources can be found on the Internet, especially those written by Jo Stichbury (personally I would recommend this one a weblog completely dedicated to descriptors, but there are also other ones which can be found on Symbian developer communities or on Nokia forums), some misunderstandings still persist.

Personally I almost do not know anything about descriptors, I have just some scarce knowledge about Symbian in general, but I am struggling to improve.

Let me tell you how I see the things from a beginner perspective.

First of all two things are important to mention just from the beginning: descriptors (which are somehow equivalent of C arrays) are safer than ordinary C arrays and they are heavily used in transferring data, either on binary format or text.

Before going deeper into descriptors’ understanding I think it is required to clarify why is it so unsafe to use null terminated strings, like those implemented in C.

What is a nul (and it is rather more correct to call it NUL instead of NULL, which has more to do with dynamically allocated pointers – NULL could be something like ((void*)0)) terminated character array?

Let’s turn to Wikipedia and see what is there explained.