Re: [9fans] bug in authdial()

[erik quanstrom]

On Sat May 21 15:19:06 PDT 2016, 9...@9netics.com wrote:
> > <   char exitsts[2*ERRMAX];
> > ---
> >>    Waitmsg *exitsts = nil;
> > 
> > is likely to generate used-and-not-set on amd64.
> > 
> > - erik
> 
> i'm not sure i understand how. can you explain?

since the only code path that uses exitsts sets it unconditionally,
setting a declaration time is going to be optimized out.  when the
optimizer elides setting of a variable it emits the set and not used
diagnostic.

gcc doesn't do this with the usual flags, which is why it may be unexpected.
i've included a test program that makes this a little easier to read.
the test program emits the diagnostic "warning: warn.c:9 set and not used: s"

- erik

---
#include <u.h>
#include <libc.h>

void
main(void)
{
        char *s;

        s = nil;
        s = "xyz";
        print("s=%s\n", s);
        exits("");
}