From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andrew Cagney <ac131313@cygnus.com>
To: David Taylor <taylor@cygnus.com>, gdb-patches@sources.redhat.com, Michael Snyder <msnyder@cygnus.com>
Subject: Re: [RFA] regcache.c (register_fetched) + related changes
Date: Wed, 28 Feb 2001 18:27:00 -0000
Message-id: <3A9DB30C.62C07D74@cygnus.com>
References: <200102282113.QAA18390@texas.cygnus.com> <3A9D8655.C57F3DB6@cygnus.com>
X-SW-Source: 2001-02/msg00541.html

Andrew Cagney wrote:

> Yes.  My suggestion, hinted at in the last e-mail, would be to combine
> the two disjoint operations:
> 
>         supply_register(....);
>         set_register_cache(..., -1)
> 
> into an atomic cache transaction:
> 
>         supply_unavailable_register(....)

PS/2:  The comment on supply_register() in regcache.c reads:

   [....]
   If VAL is a NULL pointer, then it's probably an unsupported register.
   We just set its value to all zeros.  We might want to record this
   fact, and report it to the users of read_register and friends.  */

Nothing is recorded.  The register is simply set to zero.

Checking the target code, this ``feature'' is used a lot (eg
alphabsd-nat.c):

      if (CANNOT_FETCH_REGISTER (i))
        supply_register (i, NULL);
      else
        supply_register (i, (char *) &gregsetp->r_regs[i]);

GDB really should record this cache state giving:

	valid
	unavailable
	invalid
	unsupported

Alternativly, the states unavailable and unsupported could be merged.

remote.c, which puts the cache into ``unavailable'' state, also writes
zeros into the register.

Thoughts? Especially from the people that added introspect support.

	Andrew