Atmel CAVR-4 Manual De Usuario

CAVR-4

Part 2. Compiler reference

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

 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

 is equivalent to 

intptr_t

, with the exception that it is unsigned.

The members of a 

struct

 are stored sequentially in the order in which they are 

declared: the first member has the lowest memory address.

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.

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.

-v0

 and -v1

signed

 int

-v2

, -v3, -v4, -v5, and -v6

signed

 long