Raymond Toy pushed to branch issue-473-make-cr-exp-signal-underflow at cmucl / cmucl

Commits:

• c84c6c27
  by Raymond Toy at 2026-02-16T18:52:48-08:00

  Make core-math exp silently return NaN when given NaN
  
  This makes exp match what many other core-math routines do with NaN,
  like log, sin, tan, and sinh, which silently return NaN.
  
  This also makes it match what fdlibm does, as mentioned in the
  comments in e_exp.c.
  

1 changed file:

• src/lisp/irrat.c

Changes:

 lisp_exp(double x)

 {

 #ifdef FEATURE_CORE_MATH

+    /*

+     * For consistency, silently return NaN when x is NaN.  Do not

+     * signal an invalid operation, even if invalid operation trap is

+     *  enabled.  This is what fdlibm does, and also what many of the

+     *  other core-math routines do.

+     */

+

+    if (isnan(x)) {

+	return x;

+    }

+    

     /*

      * Can't depend on cr_exp to signal underflow.  It seems the

      * underflow has been constant-folded to zero.  Hence, check for