The order of volatile accesses is undefined in this statement
Technical Note 99411
1/5/2018 11:33 AM
The message below is issued if two or more variables in a C statement are volatile.
Warning[Pa082]: undefined behavior: the order of volatile accesses is undefined in this statement
The important information in the message is the text ...order of volatile accesses is undefined... That is, the IAR C/C++ Compiler will (because it follows the ISO/ANSI standard) access the variables in an order that is not defined.
volatile is (typically) used for variables that are accessed from several threads in the application and for the Special Function Registers that are the connection in/out of the chip. Study how the
volatile variables in this C statement are used and decide if you must make a change or not.
One way to avoid the warning is to break up the C statement, so that each new C statement holds only one access to a
volatile variable. In following example, the variables
ADC are volatile and will issue the Warning[Pa082].
This code example will give the [Pa082] warning:
intAnalogSample[internalChannelSelect] = ADC[internalChannelSelect];
The following change will make the C source predictable. Note that the temporary variables are NOT volatile:
i = internalChannelSelect;
k = ADC[i];
intAnalogSample[i] = k;
To avoid the warning you can break up the C statement, so that each C statement holds only one access to a
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