Update pow() tests to check for both errno==EDOM _and_ result==Nan, and

document why this happens.  Remove exp() errno check because not needed.

diff --git a/src/backend/utils/adt/float.c b/src/backend/utils/adt/float.c
index 441f766f0ba4dd38b85377de930fa2010b100a1b..128f147debd342b9f440d3cc9e54ebb7b360a8d0 100644 (file)
--- a/src/backend/utils/adt/float.c
+++ b/src/backend/utils/adt/float.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *       $PostgreSQL: pgsql/src/backend/utils/adt/float.c,v 1.138 2007/01/03 19:34:23 tgl Exp $
+ *       $PostgreSQL: pgsql/src/backend/utils/adt/float.c,v 1.139 2007/01/03 22:05:00 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1440,17 +1440,24 @@ dpow(PG_FUNCTION_ARGS)
 
        /*
         * pow() sets errno only on some platforms, depending on whether it
-        * follows _IEEE_, _POSIX_, _XOPEN_, or _SVID_, and some return Nan,
-        * so we check and set result properly.
+        * follows _IEEE_, _POSIX_, _XOPEN_, or _SVID_, so we try to avoid
+        * using errno.  However, some platform/CPU combinations return
+        * errno == EDOM and result == Nan, so we have to check for that and
+        * set result properly.  For example, Linux on Pentium, pre-Xeon
+        * hardware returns EDOM/Nan for (-1) ^ 1e19, but (-1) ^ 1e18 retuns
+        * 1 -- basically a negative base raised to a very high power causes
+        * it on some CPUs.
         */
        errno = 0;
        result = pow(arg1, arg2);
-       if (errno == ERANGE || isnan(result))
+       if (errno == EDOM && isnan(result))
        {
                if ((fabs(arg1) > 1 && arg2 >= 0) || (fabs(arg1) < 1 && arg2 < 0))
                        result = (arg1 >= 0) ? get_float8_infinity() : -get_float8_infinity();
-               else
+               else if (fabs(arg1) != 1)
                        result = 0;
+               else
+                       result = 1;
        }
        
        CHECKFLOATVAL(result, isinf(arg1) || isinf(arg2), arg1 == 0);
@@ -1467,20 +1474,7 @@ dexp(PG_FUNCTION_ARGS)
        float8          arg1 = PG_GETARG_FLOAT8(0);
        float8          result;
 
-       /*
-        * exp() sets errno only on some platforms, depending on whether it
-        * follows _IEEE_, _POSIX_, _XOPEN_, or _SVID_, and some return Nan,
-        * so we check and set result properly.
-        */
-       errno = 0;
        result = exp(arg1);
-       if (errno == ERANGE || isnan(result))
-       {
-               if (arg1 >= 0)
-                       result = get_float8_infinity();
-               else
-                       result = 0;
-       }
 
        CHECKFLOATVAL(result, isinf(arg1), false);
        PG_RETURN_FLOAT8(result);