Re: g77 testsuite failures under hpux 10.20

["John David Anglin" <dave at hiauly1 dot hia dot nrc dot ca>]

> >   In message <200007062319.TAA11417@hiauly1.hia.nrc.ca>you write:
> >  > The obstack_grow call has walked over the rtl.
> > OK.  This is odd since I don't think the RTL should have been allocated
> > in an obstack to begin with since RTL items are part of the garbage
> > collected memory, not obstacked memory.
> 
> It appears that allocation in obstacked memory occurs if ggc_p is zero
> (cf, ggc.h:27):
> 
> /* Language-specific code defines this variable to be either one (if
>    it wants garbage collection), or zero (if it does not).  */
>    extern int ggc_p;

ggc_p is 1, so this is not the problem.

The string is allocated in obstacked memory in hppa_encode_label:

/* In HPUX 8.0's shared library scheme, special relocations are needed
   for function labels if they might be passed to a function
   in a shared library (because shared libraries don't live in code
   space), and special magic is needed to construct their address.

   For reasons too disgusting to describe storage for the new name
   is allocated either on the saveable_obstack (released at function
   exit) or on the permanent_obstack for things that can never change
   (libcall names for example). */

void
hppa_encode_label (sym, permanent)
     rtx sym;
     int permanent;
{
  const char *str = XSTR (sym, 0);
  int len = strlen (str);
  char *newstr;

  newstr = obstack_alloc ((permanent ? &permanent_obstack : saveable_obstack),
			  len + 2);

  if (str[0] == '*')
    *newstr++ = *str++;
  strcpy (newstr + 1, str);
  *newstr = '@';
  XSTR (sym,0) = newstr;
}
/* Construct a constant descriptor for the rtl-expression X.
   It is up to the caller to enter the descriptor in the hash table.  */

hppa_encode_label is called from make_decl_rtl as follows:

#0  hppa_encode_label (sym=0x40098108, permanent=0)
    at ../../gcc/config/pa/pa.c:5963
#1  0x1afd9c in make_decl_rtl (decl=0x4009c700, asmspec=0x0, top_level=1)
    at ../../gcc/varasm.c:829

Finally, the string allocated in hppa_encode_label is overwritten in
record_constant_rtx:

static struct constant_descriptor *
record_constant_rtx (mode, x)
     enum machine_mode mode;
     rtx x;
{
  struct constant_descriptor *ptr;
  char *label;
  rtx rtl;
  struct rtx_const value;

  decode_rtx_const (mode, x, &value);

  /* Put these things in the saveable obstack so we can ensure it won't
     be freed if we are called from combine or some other phase that discards
     memory allocated from function_obstack (current_obstack).  */
  obstack_grow (saveable_obstack, &ptr, sizeof ptr);
  obstack_grow (saveable_obstack, &label, sizeof label);
  obstack_grow (saveable_obstack, &rtl, sizeof rtl);

  /* Record constant contents.  */
  obstack_grow (saveable_obstack, &value, sizeof value);

  return (struct constant_descriptor *) obstack_finish (saveable_obstack);
}

If I was to guess, the obstack must be popped at some point, possibly
after the main program (this is where the @do_lio string is allocated).

Dave
-- 
J. David Anglin                                  dave.anglin@nrc.ca
National Research Council of Canada              (613) 990-0752 (FAX: 952-6605)