Question

I am going through a c++ code base and in the header file (Executor.h) there is the public field definition

typedef std::pair<ExecutionState*,ExecutionState*> StatePair;

Inside the cpp file (Executor.cpp) there is a line

Executor::StatePair 
Executor::fork(ExecutionState &current, ref<Expr> condition, bool isInternal) { /* function definition */ }

in which this field is referenced right before one of the member function definitions

What is the purpose of stating the field name right before the definition ? Is it scoping issues ?

Thanks

Answer 1

The StatePair is a type. Its purpose in front of the function definition is to state the return type of the function

Note the typedef in the definition of StatePair. It introduces a name alias for a type. In this case std::pair<ExecutionState*,ExecutionState*> will also be called StatePair, so you don’t have to write that long type name

The return type of a function names the type that the value returned from the function must belong to. E.g. in the case of

int f();

the function f must return an integer (int), so we could write a definition like this:

int f() {return 0;}

there could be other statements in the function body, but the last one has to be a return with an integer value after it (in the bavode example the value is 0)

As C++ does not care about new lines (treats them as regular white-space), the format

int
f() {...}

is the same as for the above function.