Specifications

CAVR-4
Part 2. Compiler reference
Data representation
143
ptrdiff_t
ptrdiff_t is the type of the signed integer required to hold the difference between two
pointers to elements of the same array. The following table shows the
typedef of
ptrdiff_t depending on the processor option:
Note: Subtracting the start address of an object from the end address can yield a
negative value, because the object can be larger than what the
ptrdiff_t can represent.
See this example:
char buff[60000]; /* Assuming ptrdiff_t is a 16-bit */
char *p1 = buff; /* signed integer type. */
char *p2 = buff + 60000;
ptrdiff_t diff = p2 - p1;
intptr_t
intptr_t is a signed integer type large enough to contain a void *. In the AVR IAR
C/C++ Compiler, the size of intptr_t is long int when using the Large memory
model and int in all other cases.
uintptr_t
uintptr_t is equivalent to intptr_t, with the exception that it is unsigned.
Structure types
The members of a struct are stored sequentially in the order in which they are
declared: the first member has the lowest memory address.
ALIGNMENT
The struct and union types inherit the alignment requirements of their members. In
addition, the size of a
struct is adjusted to allow arrays of aligned structure objects.
GENERAL LAYOUT
Members of a struct (fields) are always allocated in the order given in the declaration.
The members are placed in memory according to the given alignment (offsets), which
always is 1.
Generic processor option Typedef
-v0 and -v1 signed int
-v2, -v3, -v4, -v5, and -v6 signed long
Table 36: ptrdiff_t typedef