Atmel CAVR-4 Manual De Usuario

CAVR-4

Descriptions of language extensions

Reference Guide

Redeclarations of 

typedef

 that occur in the same scope are allowed, but a warning is 

issued.

Assignment and pointer difference is allowed between pointers to types that are 
interchangeable but not identical; for example, 

unsigned

 

char

 * and 

char

 *. This 

includes pointers to integral types of the same size. A warning is issued.

Assignment of a string constant to a pointer to any kind of character is allowed, and no 
warning will be issued.

Assignment of pointers is allowed in cases where the destination type has added type 
qualifiers that are not at the top level (for example, 

int

 

**

 to 

int

 

const **

). It is also 

allowed to compare and take the difference of such pointers.

External and static declarations in other scopes are visible. In the following example, the 
variable 

y

 can be used at the end of the function, even though it should only be visible 

in the body of the 

if

 statement. A warning is issued.

int test(int x)

{

  if (x)

  {

    extern int y;

    y = 1;

  }

  return y;

}

A non-

lvalue

 array expression is converted to a pointer to the first element of the array 

when it is used.