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Variable Signess : Portability Problem

As you might have already noticed I released my first e-book about these tips & tricks. At the same time I changed the service name, it is not anymore programming tips & tricks, now it is software development tips & tricks. But don’t worry, you are already getting newer information as this trick won’t be in that book.

So, have you ever considered variable signess?

Variable signess means signed or unsigned variable. Let’s use an classic example of char signess.

• Unsigned char (range : 0 -> 255)
• Signed char (range : -127 -> 127)

What does this mean? Well it means if you define char variable as 255 and the it is signed it becomes -1. But the real thing why you should care about this is that on different platforms the default char type has different signess!

Default char signess :

• Windows / Linux : signed char
• Power PC / ARM : unsigned char

So now if you code do this : char myValue = 255; – in Windows it will be -1, but in Power PC it is 255! Yes, this leads to some serious problems. But there is a solution, typedef your own char type with predefined signess :

typedef unsigned char MyUChar; – and – typedef signed char MySChar; – for example. Now you can do this : MyUChar myValue = 255; – and it will be right in Windows and in Power PC.