[PATCH] gas: range-check 3rd argument of .align et al

[Jan Beulich]

Negative values would have been silently converted to large positive
ones, which may not be the user's intention. Similarly overly large
values would have been silently truncated. Warn them instead, and zap
such values.
---
I've noticed this while pondering whether to assign meaning to negative
values: Don't pad if fewer than the (negated) number would be inserted.
Thoughts towards such an extension?

In !BFD64 configurations the "less than 0" check could in principle
cause regressions, as large enough positive values would appear to be
negative once returned from get_absolute_expression(). Such code would
break anyway, however, once assembled with a BFD64 assembler (and that
property may appear simply because of some secondary target that other
binutils as a whole are configured to also support).

--- a/gas/read.c
+++ b/gas/read.c
@@ -1598,7 +1598,13 @@ s_align (signed int arg, int bytes_p)
       else
 	{
 	  ++input_line_pointer;
-	  max = get_absolute_expression ();
+	  offsetT val = get_absolute_expression ();
+	  max = val;
+	  if (val < 0 || max != val)
+	    {
+	      as_warn (_("ignoring out of range alignment maximum"));
+	      max = 0;
+	    }
 	}
     }