Atmel CAVR-4 Manual De Usuario

CAVR-4

Part 2. Compiler reference

Note: ISO/ANSI C allows extra commas in similar situations, for example after the last 
element of the initializers to an array. The reason is, that it is easy to get the commas 
wrong if parts of the list are moved using a normal cut-and-paste operation.

enum 

{

   kOne,

   kTwo,   /* This is now allowed. */

};

A warning is issued if the semicolon at the end of a 

struct

 or union specifier is missing.

In operations on pointers, a pointer to 

void

 is always implicitly converted to another 

type if necessary, and a null pointer constant is always implicitly converted to a null 
pointer of the right type if necessary. In ISO/ANSI C, some operators allow such things, 
while others do not allow them.

In ISO/ANSI C, a label must be followed by at least one statement. Therefore, it is illegal 
to place the label at the end of a block. In the AVR IAR C/C++ Compiler, a warning is 
issued.

To create a standard-compliant C program (so that you will not have to see the warning), 
you can place an empty statement after the label. An empty statement is a single 

;

 

(semi-colon). 

void test()

{

  if (...) goto end;

   /* Do something */

  end:  /* Illegal at the end of block. */

}

Note: This also applies to the labels of switch statements.