> > +#define DEBUG(Expression) \
> > + do { \
> > + _Pragma("GCC diagnostic push") \
> > + _Pragma("GCC diagnostic ignored \"-Wunused-value\"") \
> > + if ((FALSE)) { \
> > + (VOID) Expression; \
>
> So what is the point of the VOID cast here? Usually, these are added
> to avoid unused value warnings, but these are disabled explicitly via
> the pragma.
```
$ cat test.c
static int a = 0;
void foo()
{
if ((0)) {
(void)((void *)(long)0, a);
}
}
$ clang -c -Wall test.c -o test.o
test.c:6:12: warning: expression result unused; should this cast be to
'void'? [-Wunused-value]
(void)((void *)(long)0, a);
^ ~
1 warning generated.
```
Without the pragmas, various DEBUG statements sent into the macro
generate unused *value* warnings exactly such as the above. Once we
suppress these unused value warnings, the existence of the
comma-operator separated list of values, cast to void, avoids unused
*variable* warnings, such as the unused variable warning that would
otherwise occur about `a` above - allowing `a` to instead just be
optimised away when it becomes unused in this way, as we want.
For the other questions, let me get back to you! Thank you.
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