MPLAB C Compiler for PIC24 MCUs and dsPIC DSCs ... - Microchip

Using the Compiler on the Command Line
TABLE 3-6: WARNING/ERROR OPTIONS NOT IMPLIED BY -WALL
Option Definition
-W Print extra warning messages for these events:
• A nonvolatile automatic variable might be changed by a
call to longjmp. These warnings are possible only in
optimizing compilation. The compiler sees only the calls
to setjmp. It cannot know where longjmp will be called;
in fact, a signal handler could call it at any point in the
code. As a result, a warning may be generated even
when there is in fact no problem, because longjmp
cannot in fact be called at the place that would cause a
problem.
• A function could exit both via return value; and
return;. Completing the function body without passing
any return statement is treated as return;.
• An expression-statement or the left-hand side of a
comma expression contains no side effects. To suppress
the warning, cast the unused expression to void. For
example, an expression such as x[i,j] will cause a
warning, but x[(void)i,j] will not.
• An unsigned value is compared against zero with < or