Microchip Technology XC8 Standard Compiler (Workstation) SW006021-1 SW006021-1 User Manual

®

DS52053A-page 22

 2012 Microchip Technology Inc.

2.4.11.2

DIFFERENCES

All compilers have performed right shifting as described in this section.

2.4.11.3

MIGRATION TO THE CCI

No action required.

If a union defines several members of different types and you use one member identi-
fier to try to access the contents of another (whether any conversion is applied to the 
result) is implementation-defined behavior in the standard. In the CCI, no conversion is 
applied and the bytes of the union object are interpreted as an object of the type of the 
member being accessed, without regard for alignment or other possible invalid condi-
tions.

2.4.12.1

EXAMPLE

The following shows an example of a union defining several members.

union {

signed char code;

unsigned int data;

float offset;

} foobar;

Code that attempts to extract offset by reading data is not guaranteed to read the 
correct value.

float result;

result = foobbar.data;

2.4.12.2

DIFFERENCES

All compilers have not converted union members accessed via other members.

2.4.12.3

MIGRATION TO THE CCI

No action required.

The type of a bit-field specified as a plain int will be identical to that of one defined 
using unsigned int. This is quite different to other objects where the types int, 
signed

 and signed int are synonymous. It is recommended that the signedness of 

the bit-field be explicitly stated in all bit-field definitions.

2.4.13.1

EXAMPLE

The following shows an example of a structure tag containing bit-fields which are 
unsigned integers and with the size specified.

struct OUTPUTS {

int direction :1;

int parity    :3;

int value     :4;

};