eiffel-org/documentation/trunk/eiffel/Language_reference/void-safe-programming-eiffel/index.wiki

[[Property:title|Void-safe programming in Eiffel]]
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=About void-safe software development using Eiffel=

When you develop software in Eiffel, you can be assured (at compile time) that your system will not attempt (at run time) to apply a feature to a void reference. That is, Eiffel prevents situations in which systems fail at run time with the error: "Feature call on void target".

Throughout the history of Eiffel, a small number of important new capabilities, agents for example, have been added. Always these innovations have added significantly to the power of Eiffel, and have been carefully designed to cause a minimum of impact on existing software. Void-safe Eiffel is such an innovation. 

However, it is not quite right to refer to it as "void-safe Eiffel". In fact, it is Eiffel ... and it is void-safe, just as it is statically typed.  

Still, the reality is that Eiffel did not always provide void-safety, and that has the potential to cause confusion among both new and seasoned Eiffel developers. New developers will find for awhile that parts of the Eiffel documentation were written prior to the advent of void-safety, and may not have been updated yet. Experienced Eiffel programmers will find that software that compiled in versions of Eiffel before it became void-safe, may not compile anymore with void-safe capabilities enabled. 

The result is that we must consider certain questions:

# How is void-safety defined?
# What are the specific elements of the mechanism for void-safety?
# How do these relate to Eiffel before void-safety?
# What do I need to know to produce standard Eiffel software?
# What do I need to know to convert my existing systems to be standard?

To find some answers, continue reading this chapter.