Atmel CAVR-4 Manual De Usuario

CAVR-4

Descriptions of language extensions

Reference Guide

The following piece of code will generate a warning: 

switch (x)

{

case 1:

  ...;

  break;

default:

}

A good way to convert this into a standard-compliant C program is to place a 

break;

 

statement after the 

default:

 label.

An empty declaration (a semicolon by itself) is allowed, but a remark is issued (provided 
that remarks are enabled).

This is useful when preprocessor macros are used that could expand to nothing. 
Consider the following example. In a debug build, the macros 

DEBUG_ENTER

 and 

DEBUG_LEAVE

 could be defined to something useful. However, in a release build they 

could expand into nothing, leaving the 

;

 character in the code:

void test()

{

  DEBUG_ENTER();

  do_something();

 

  DEBUG_LEAVE();

}

ISO/ANSI C requires that all initializer expressions of static arrays, 

structs

, and 

unions

 are enclosed in braces. 

Single-value initializers are allowed to appear without braces, but a warning is issued.

In the AVR IAR C/C++ Compiler, the following expression is allowed:

struct str

{

  int a;

} x = 10;