isfinite on HP-UX 11

[Bruno Haible]

On HP-UX 11.11, with CC="cc -Ae -O", I'm observing this test failure:

  test-isfinite.c:54: assertion failed
  sh[10]: 1712 Abort(coredump)
  FAIL: test-isfinite

The cause is that isfinite.c is miscompiled by "cc -O": The comparison
x - x == 0 is "simplified" to x == x; this simplification is wrong for
Infinity values. This patch avoids this bug:


2010-12-31  Bruno Haible  <address@hidden>

        isfinite: Avoid compiler bug of "cc -O" on HP-UX 11.11.
        * lib/isfinite.c (zerof, zerod, zerol): New variables.
        (gl_isfinitef, gl_isfinited, gl_isfinitel): Use them instead of literal
        zero.

--- lib/isfinite.c.orig Sat Jan  1 03:49:46 2011
+++ lib/isfinite.c      Sat Jan  1 03:44:20 2011
@@ -23,17 +23,30 @@
 #include "isnand-nolibm.h"
 #include "isnanl-nolibm.h"
 
+/* The "cc" compiler on HP-UX 11.11, when optimizing, simplifies the test
+   x - y == 0.0  to  x == y, a simplification which is invalid when x and y
+   are Infinity.  Disable this optimization.  */
+#if defined __hpux && !defined __GNUC__
+static float zerof;
+static double zerod;
+static long double zerol;
+#else
+# define zerof 0.f
+# define zerod 0.
+# define zerol 0.L
+#endif
+
 int gl_isfinitef (float x)
 {
-  return !isnanf (x) && x - x == 0.f;
+  return !isnanf (x) && x - x == zerof;
 }
 
 int gl_isfinited (double x)
 {
-  return !isnand (x) && x - x == 0.;
+  return !isnand (x) && x - x == zerod;
 }
 
 int gl_isfinitel (long double x)
 {
-  return !isnanl (x) && x - x == 0.L;
+  return !isnanl (x) && x - x == zerol;
 }