Re: 2.6.14 assorted warnings

[Al Viro <viro@ftp.linux.org.uk>]

On Sun, Oct 30, 2005 at 10:15:31PM +0000, Alan Cox wrote:
> gcc is a *LOT* smarter than you give it credit for. It will not warn for
> cases where it isn't able to tell how foo is used passed with &foo. It
> will warn for cases where it can

static inline __attribute__((always_inline)) int bar(int n, int *idx)
{
        if (n != 1) 
                return 0; 
        *idx = 1;
        return 1;  
}
void baz(int *v, int n)
{
        int idx;
        int p = bar(n, &idx);
        if (__builtin_expect(!p, 0))
                return; 
        *v |= idx;
}

and try gcc -Wall on that.  Watch it warn about idx being possibly
uninitialized.  Replace __builtin_expect(!p, 0) with !p and see
the warning go away.  That, BTW, is a trimmed-down source of bogus
warning in bio.c.  And a lot of its analogs all over the tree.