From: Zhangjin Wu
> Sent: 14 August 2023 11:42
...
> [...]
> > > > Sure it's not pretty, and I'd rather just go back to SET_ERRNO() to be
> > > > honest, because we're there just because of the temptation to remove
> > > > lines that were not causing any difficulties :-/
> > > >
> > > > I think we can do something in-between and deal only with signed returns,
> > > > and explicitly place the test for MAX_ERRNO on the two unsigned ones
> > > > (brk and mmap). It should look approximately like this:
> > > >
> > > > #define __sysret(arg) \
> > > > ({ \
> > > > __typeof__(arg) __sysret_arg = (arg); \
> > > > (__sysret_arg < 0) ? ({ /* error ? */ \
> > > > SET_ERRNO(-__sysret_arg); /* yes: errno != -ret */ \
> > > > ((__typeof__(arg)) -1); /* return -1 */ \
I'm pretty sure you don't need the explicit cast.
(It would be needed for a pointer type.)
Can you use __arg < ? SET_ERRNO(-__arg), -1 : __arg
Thinking, maybe it should be:
#define __sysret(syscall_fn_args)
({
__typeof__(syscall_fn_args) __rval = syscall_fn_args;
__rval >= 0 ? __rval : SET_ERRNO(-__rval), -1;
})
Since, IIRC, the usage is return __sysret(sycall_fn(args));
I'm not sure how public SET_ERRO() is.
But it could include the negate have the value of -1 cast to its argument type?
I think:
error = -(int)(long)(arg + 0u);
will avoid any sign extension - the (int) might not even be needed.
David
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