# 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 123
Take care when comparing (subtracting) pointers. For example:
if(cp1 == cp2)
; take appropriate action
The ANSI C standard only allows pointer comparisons when the two pointer targets are
the same object. The address may extend to one element past the end of an array.
Comparisons of pointers to integer constants are even more risky, for example:
if(cp1 == 0x246)
; take appropriate action
A NULL pointer is the one instance where a constant value can be safely assigned to a
pointer. A NULL pointer is numerically equal to 0 (zero), but since they do not guarantee
to point to any valid object and should not be dereferenced, this is a special case
imposed by the ANSI C standard. Comparisons with the macro NULL are also allowed.
8.8 COMPLEX DATA TYPES
The compiler supports complex data types. You can declare both complex integer
types and complex floating types, using the keyword __complex__.
For example, __complex__ float x; declares x as a variable whose real part and
imaginary part are both of type float. __complex__ short int y; declares y to
have real and imaginary parts of type short int.
To write a constant with a complex data type, use the suffix i or j (either one; they
are equivalent). For example, 2.5fi has type __complex__ float and 3i has type
__complex__ int. Such a constant is a purely imaginary value, but you can form
any complex value you like by adding one to a real constant.
To extract the real part of a complex-valued expression exp, write __real__ exp.
Similarly, use __imag__ to extract the imaginary part. For example;
__complex__ float z;
float r;
float i;
r =
__real__ z;
i =
__imag__ z;
The operator, ~, performs complex conjugation when used on a value with a complex
type.
The compiler can allocate complex automatic variables in a noncontiguous fashion; its
even possible for the real part to be in a register while the imaginary part is on the stack
(or vice-versa). The debugging information format has no way to represent noncontig-
uous allocations like these, so the compiler describes noncontiguous complex
variables as two separate variables of noncomplex type. If the variables actual name
is foo, the two fictitious variables are named foo$real and foo$imag.

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