diff options
Diffstat (limited to 'src/backend/utils/adt/float.c')
| -rw-r--r-- | src/backend/utils/adt/float.c | 34 |
1 files changed, 23 insertions, 11 deletions
diff --git a/src/backend/utils/adt/float.c b/src/backend/utils/adt/float.c index 08ebbf4678e..086631dd19f 100644 --- a/src/backend/utils/adt/float.c +++ b/src/backend/utils/adt/float.c @@ -1583,7 +1583,7 @@ dpow(PG_FUNCTION_ARGS) if (arg2 == floor(arg2)) { /* y is integral; it's odd if y/2 is not integral */ - double halfy = arg2 * 0.5; /* should be computed exactly */ + double halfy = arg2 / 2; /* should be computed exactly */ if (halfy != floor(halfy)) yisoddinteger = true; @@ -1608,17 +1608,29 @@ dpow(PG_FUNCTION_ARGS) if (errno == EDOM || isnan(result)) { /* - * We eliminated all the possible domain errors above, or should - * have; but if pow() has a more restrictive test for "is y an - * integer?" than we do, we could get here anyway. Historical - * evidence suggests that some platforms once implemented the test - * as "y == (long) y", which of course misbehaves beyond LONG_MAX. - * There's not a lot of choice except to accept the platform's - * conclusion that we have a domain error. + * We handled all possible domain errors above, so this should be + * impossible. However, old glibc versions on x86 have a bug that + * causes them to fail this way for abs(y) greater than 2^63: + * + * https://sourceware.org/bugzilla/show_bug.cgi?id=3866 + * + * Hence, if we get here, assume y is finite but large (large + * enough to be certainly even). The result should be 0 if x == 0, + * 1.0 if abs(x) == 1.0, otherwise an overflow or underflow error. */ - ereport(ERROR, - (errcode(ERRCODE_INVALID_ARGUMENT_FOR_POWER_FUNCTION), - errmsg("a negative number raised to a non-integer power yields a complex result"))); + if (arg1 == 0.0) + result = 0.0; /* we already verified y is positive */ + else + { + double absx = fabs(arg1); + + if (absx == 1.0) + result = 1.0; + else if (arg2 >= 0.0 ? (absx > 1.0) : (absx < 1.0)) + float_overflow_error(); + else + float_underflow_error(); + } } else if (errno == ERANGE) { |