# Vault 7: Projects

This publication series is about specific projects related to the Vault 7 main publication.

### Protego

# MPLAB XC16 C-Compiler

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Supported Data Types and Variables
 2012-2013 Microchip Technology Inc. DS50002071C-page 121
8.7 POINTER TYPES
There are two basic pointer types supported by the MPLAB XC16 C Compiler: data
pointers and function pointers. Data pointers hold the addresses of variables which can
be indirectly read, and possibly indirectly written, by the program. Function pointers
hold the address of an executable function which can be called indirectly via the pointer.
8.7.1 Combining Type Qualifiers and Pointers
It is helpful to first review the ANSI C standard conventions for definitions of pointer
types.
Pointers can be qualified like any other C object, but care must be taken when doing
so as there are two quantities associated with pointers. The first is the actual pointer
itself, which is treated like any ordinary C variable and has memory reserved for it. The
second is the target, or targets, that the pointer references, or to which the pointer
points. The general form of a pointer definition looks like the following:
target_type_&_qualifiers * pointers_qualifiers pointers_name;
Any qualifiers to the right of the * (i.e., next to the pointers name) relate to the pointer
variable itself. The type and any qualifiers to the left of the * relate to the pointers tar-
gets. This makes sense since it is also the * operator that dereferences a pointer, which
allows you to get from the pointer variable to its current target.
Here are three examples of pointer definitions using the volatile qualifier. The fields
in the definitions have been highlighted with spacing:
volatile int * vip ;
int * volatile ivp ;
volatile int * volatile vivp ;
The first example is a pointer called vip. It contains the address of int objects that
are qualified volatile. The pointer itself  the variable that holds the address  is not
volatile; however, the objects that are accessed when the pointer is dereferenced
are treated as being volatile. In other words, the target objects accessible via the
pointer may be externally modified.
The second example is a pointer called ivp which also contains the address of int
objects. In this example, the pointer itself is volatile, that is, the address the pointer
contains may be externally modified; however, the objects that can be accessed when
dereferencing the pointer are not volatile.
The last example is of a pointer called vivp which is itself qualified volatile, and
which also holds the address of volatile objects.
Bear in mind that one pointer can be assigned the addresses of many objects; for
example, a pointer that is a parameter to a function is assigned a new object address
every time the function is called. The definition of the pointer must be valid for every
target address assigned.
Note: Care must be taken when describing pointers. Is a const pointer a pointer
that points to const objects, or a pointer that is const itself? You can talk
about pointers to const and const pointers to help clarify the definition,
but such terms may not be universally understood.

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