Atmel CAVR-4 Manual De Usuario

CAVR-4

Part1. Using the compiler

The following is a list of programming techniques that will, when followed, save 
memory and stack space:

●

If stack space is limited, avoid long call chains and recursive functions.

●

Avoid using large non-scalar types, such as structures, as parameters or return type; 
in order to save stack space, you should instead pass them as pointers or, in C++, as 
references.

It is possible to declare and define functions using one of two different styles:

●

Prototyped

●

Kernighan & Ritchie C (K&R C)

Both styles are included in the C standard; however, it is recommended to use the 
prototyped style, since it makes it easier for the compiler to find problems in the code. 
In addition, using the prototyped style will make it possible to generate more efficient 
code, since type promotion (implicit casting) is not needed. The K&R style is only 
supported for compatibility reasons.

To make the compiler verify that all functions have proper prototypes, use the compiler 
option Require prototypes (

--require_prototypes

).

In prototyped function declarations, the type for each parameter must be specified.

int test(char, int);

/* declaration */

int test(char a, int b)

/* definition */

{

  .....

}

In K&R style—traditional pre-ISO/ANSI C—it is not possible to declare a function 
prototyped. Instead, an empty parameter list is used in the function declaration. Also, 
the definition looks different.

int test(); 

/* old declaration */

int test(a,b) 

/* old definition */

char a;

int b;

{

  .....

}