On Mon, Jun 30, 2014 at 11:37:50PM +0200, Marc Glisse wrote: > On Mon, 30 Jun 2014, Jeff Law wrote: > > >On 06/29/14 03:22, Marc Glisse wrote: > >> > >>After looking at PR 61597, I updated the 2 conditions to: > >> > >>+ if ((TREE_CODE (valbase) == VAR_DECL > >>+ && !is_global_var (valbase)) > >>+ || TREE_CODE (valbase) == PARM_DECL) > >> > >>a PARM_DECL is a local variable and returning its address is wrong, > >>isn't it? > >Right. It can live in either a caller or callee allocated slot. > > The "caller" case scares me a bit. Is it really wrong to return the > address in that case? The slot still exists after returning if the > caller is responsible for it.
At least on powerpc64, which uses a caller allocated parameter save area, returning the address of something in the parameter save area merits a warning. The ABIs explicitly state that the parameter save area is not preserved over function calls. Also note that anything left in a caller allocated parameter save area will potentially be trashed by arguments written for the next call. -- Alan Modra Australia Development Lab, IBM
