passing address of floating-point parameter

[Dale Worley]

In article <64623 at bbn.BBN.COM> cjross at bbn.com (chris ross) writes:

   foo (x, y)
   float x, y;
   { }

   Apparently, the Sun and MIPS compilers do not hide the fact that the
   parameter in the first routine is actually on the stack as a (double).
   Should they, or, as with va_arg, must the programmer explicitly take the
   type promotion into account?  Does ANSI specify the proper behavior?

According to ANSI C, x and y are passed in as doubles but must be
converted to floats upon entry.  In particular, &x has type "pointer
to float".  However, most K+R compilers promote x and y to doubles, so
&x has type "pointer to double".  That is, not only is the value
passed in as a double, it remains a double once it is passed in.
Section 3.7.1 of the Rationale describes this situation, and notes it
as a "Quiet Change".

Dale Worley		Compass, Inc.			worley at compass.com
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