On June 7, 2014 1:54:06 PM CEST, Steven Bosscher <stevenb....@gmail.com> wrote: >On Sat, Jun 7, 2014 at 12:59 PM, Eric Botcazou wrote: >>> >In Ada we don't mark (external) variables as addressable if we >don't >>> >see their address taken. >>> >>> You have to (now). The testing was of course to detect this... >> >> Well, you need to define what TREE_ADDRESSABLE means now, because >according to >> >> /* In VAR_DECL, PARM_DECL and RESULT_DECL nodes, nonzero means >address >> of this is needed. So it cannot be in a register. >> [...] >> #define TREE_ADDRESSABLE(NODE) ((NODE)->base.addressable_flag) >> >> your change is clearly wrong and the Ada compiler clearly right. > >"Clearly"? > >An external variable is a VAR_DECL that cannot be in a register. It >can be loaded into a register (or stored into), and for that its >address is needed. So I would expect an external variable to be marked >addressable by default. > >I was always surprised that this was not the case before Richi's >change.
Well, honza was as well, so I thought I must be wrong. > >> And auditing >> the various front-ends might also be in order here if they really >need to mark >> every single external variable as addressable to be safe wrt >aliasing. > >Right. And this should have been done (clearly ;-) ) before the patch >was committed... I thought that bootstrap and regtest plus what I remember from debug sessions was enough. Anyway, an easy fix is to make all globals TREE_ADDRESSABLE somewhere in the varpool code. But I have no idea how to audit the frontends and judge their language specific knowledge they put into deciding whether a deck may have its address taken. Richard. >Ciao! >Steven
