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Re: [PATCH] -Warray-bounds TLC


On Sat, 2015-04-18 at 00:15 +0200, Marc Glisse wrote:
> >
> > extern void bad (const char *__assertion)  __attribute__ ((__noreturn__));
> > struct link_map { long int l_ns; };
> > extern struct link_namespaces
> >  {
> >    unsigned int _ns_nloaded;
> >  } _dl_ns[1];
> > void _dl_close_worker (struct link_map *map)
> > {
> >  long int nsid = map->l_ns;
> >  struct link_namespaces *ns = &_dl_ns[nsid];
> >  (nsid != 0) ? (void) (0) : bad ("nsid != 0");
> >  --ns->_ns_nloaded;
> > }
> 
> It looks close enough to me. The actual access to _dl_ns[nsid] only ever 
> happens for an index that is out of range. The last line of the function 
> can never make sense (unreachable or undefined behavior), it is good that 
> the compiler tells you about it.

I guess, but it left me very confused because the compiler didn't point
me at the last line, it pointed me at the '*ns = &_dl_ns[nsid]' line.
If there was a lot of stuff in between that line, the line with the call
to the noreturn function, and the ns->ns_loaded line (like there is in
the real glibc), it is very hard to understand what the compiler is
trying to tell me when it only points out the first line as where the
error is.

Steve Ellcey


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