Summary

In this chapter, we have studied, in detail, one of the best C++ patterns for writing exception-safe and error-safe code. The ScopeGuard pattern allows us to schedule an arbitrary action, a fragment of C++ code, to be executed upon completion of a scope. The scope may be a function, the body of a loop, or just a scope inserted into the program to manage the lifetime of local variables. The actions that are executed to the end may be conditional on the successful completion of the scope, however, that is defined. The ScopeGuard pattern works equally well when success or failure are indicated by return codes or exceptions, although in the latter case we can automatically detect the failure (with return codes, the programmer has to explicitly specify which return values mean success and which do not). We have observed the evolution of the ScopeGuard pattern as more recent language features are used. In its optimal form, ScopeGuard provides a simple declarative way to specify post...