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PATCH: Allow a symbol set to common symbol + value


On Mon, Apr 25, 2005 at 06:20:50PM +0200, Etienne Lorrain wrote:
> --- Dave Korn <dave.korn@artimi.com> wrote:
> > > >   asm volatile (" dataPS2 = %c0 ": : "i" (&MOUSE.data.PS2));
> > 
> >   IIUIC, all you want to do here is initialise an assembler-level variable
> > with the address of MOUSE.data.PS2 at runtime, yes?  So why not make your
> > life a load easier, and do it the other way round:
> > void *dataPS2 = NULL;
> 
>   I do not think my method is that complex, not going through a variable
>  pointer but just defining a symbol to write to. With your pointer I would
>  have to read the content of the pointer and write to this address - and
>  so save another register on the stack to store the address to write to
>  in my interrupt treatment.
>  This address is known at link time so there is no need to put it in
>  a variable pointer.
> 
>   I can accept the argument of H.J. saying that the behaviour I am waiting
>  is not guarantied - but I am sure it was working perfectly in my case,
>  with binutils-2.15.
>  The address is the same, the PS2 mouse is perfectly working in Gujin,
>  and this field is only written under interrupt and only read in C.
> 
>   That is not a real problem for my application, I will initialise to
>  get the MOUSE structure in BSS instead of COMMON.
> 

"dataPS2 = MOUSE" !=  "dataPS2 = MOUSE + 4" when MOUSE is a common
symbol. "dataPS2 = MOUSE" will create a copy of MOUSE and will create
a symbol with value of "MOUSE + 4". Is that intentional? If yes, this
patch will allow "dataPS2 = MOUSE + 4". Can we change "dataPS2 = MOUSE"
to mean the value of MOUSE, not its copy?


H.J.
----
2005-04-25  H.J. Lu  <hongjiu.lu@intel.com>

	* read.c (pseudo_set): Disallow symbol set to common symbol.

	* write.c (write_object_file): Allow a symbol set to common
	symbol + value.

--- gas/read.c.set	2005-04-25 09:24:04.000000000 -0700
+++ gas/read.c	2005-04-25 11:30:11.000000000 -0700
@@ -3301,6 +3301,10 @@ pseudo_set (symbolS *symbolP)
 	{
 	  symbolS *s = exp.X_add_symbol;
 
+	  if (S_IS_COMMON (s) && exp.X_add_number == 0)
+	    as_bad (_("`%s' can't be equated to common symbol '%s'"),
+		    S_GET_NAME (symbolP), S_GET_NAME (s));
+
 	  S_SET_SEGMENT (symbolP, seg);
 	  S_SET_VALUE (symbolP, exp.X_add_number + S_GET_VALUE (s));
 	  symbol_set_frag (symbolP, symbol_get_frag (s));
--- gas/write.c.set	2005-04-20 11:12:17.000000000 -0700
+++ gas/write.c	2005-04-25 11:34:17.000000000 -0700
@@ -1928,8 +1936,13 @@ write_object_file (void)
 	  if (symbol_equated_reloc_p (symp))
 	    {
 	      if (S_IS_COMMON (symp))
-		as_bad (_("`%s' can't be equated to common symbol"),
-			S_GET_NAME (symp));
+		{
+		  expressionS *e = symbol_get_value_expression (symp);
+		  if (e->X_add_number == 0)
+		    as_bad (_("`%s' can't be equated to common symbol `%s'"),
+			    S_GET_NAME (symp),
+			    S_GET_NAME (e->X_add_symbol));
+		}
 	      symbol_remove (symp, &symbol_rootP, &symbol_lastP);
 	      continue;
 	    }


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