From: Tom Lane Date: Sun, 29 Apr 2018 19:21:45 +0000 (-0400) Subject: Avoid wrong results for power() with NaN input on some platforms. X-Git-Tag: REL9_4_18~16 X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=44ccd11cbbe60940689e35ac83a65ea4e219a983;p=postgresql Avoid wrong results for power() with NaN input on some platforms. Per spec, the result of power() should be NaN if either input is NaN. It appears that on some versions of Windows, the libc function does return NaN, but it also sets errno = EDOM, confusing our code that attempts to work around shortcomings of other platforms. Hence, add guard tests to avoid substituting a wrong result for the right one. It's been like this for a long time (and the odd behavior only appears in older MSVC releases, too) so back-patch to all supported branches. Dang Minh Huong, reviewed by David Rowley Discussion: https://postgr.es/m/75DB81BEEA95B445AE6D576A0A5C9E936A73E741@BPXM05GP.gisp.nec.co.jp --- diff --git a/src/backend/utils/adt/float.c b/src/backend/utils/adt/float.c index 0b4637f100..5b712736e7 100644 --- a/src/backend/utils/adt/float.c +++ b/src/backend/utils/adt/float.c @@ -1409,14 +1409,15 @@ dpow(PG_FUNCTION_ARGS) * pow() sets errno only on some platforms, depending on whether it * follows _IEEE_, _POSIX_, _XOPEN_, or _SVID_, so we try to avoid using * errno. However, some platform/CPU combinations return errno == EDOM - * and result == Nan for negative arg1 and very large arg2 (they must be + * and result == NaN for negative arg1 and very large arg2 (they must be * using something different from our floor() test to decide it's * invalid). Other platforms (HPPA) return errno == ERANGE and a large - * (HUGE_VAL) but finite result to signal overflow. + * (HUGE_VAL) but finite result to signal overflow. Also, some versions + * of MSVC return errno == EDOM and result == NaN for NaN inputs. */ errno = 0; result = pow(arg1, arg2); - if (errno == EDOM && isnan(result)) + if (errno == EDOM && isnan(result) && !isnan(arg1) && !isnan(arg2)) { if ((fabs(arg1) > 1 && arg2 >= 0) || (fabs(arg1) < 1 && arg2 < 0)) /* The sign of Inf is not significant in this case. */ diff --git a/src/test/regress/expected/float8-exp-three-digits-win32.out b/src/test/regress/expected/float8-exp-three-digits-win32.out index 2dd648d6b9..8e4cbb0504 100644 --- a/src/test/regress/expected/float8-exp-three-digits-win32.out +++ b/src/test/regress/expected/float8-exp-three-digits-win32.out @@ -340,6 +340,36 @@ SELECT power(float8 '144', float8 '0.5'); 12 (1 row) +SELECT power(float8 'NaN', float8 '0.5'); + power +------- + NaN +(1 row) + +SELECT power(float8 '144', float8 'NaN'); + power +------- + NaN +(1 row) + +SELECT power(float8 'NaN', float8 'NaN'); + power +------- + NaN +(1 row) + +SELECT power(float8 '1', float8 'NaN'); + power +------- + 1 +(1 row) + +SELECT power(float8 'NaN', float8 '0'); + power +------- + 1 +(1 row) + -- take exp of ln(f.f1) SELECT '' AS three, f.f1, exp(ln(f.f1)) AS exp_ln_f1 FROM FLOAT8_TBL f diff --git a/src/test/regress/expected/float8-small-is-zero.out b/src/test/regress/expected/float8-small-is-zero.out index 5da743374c..e3e004451c 100644 --- a/src/test/regress/expected/float8-small-is-zero.out +++ b/src/test/regress/expected/float8-small-is-zero.out @@ -344,6 +344,36 @@ SELECT power(float8 '144', float8 '0.5'); 12 (1 row) +SELECT power(float8 'NaN', float8 '0.5'); + power +------- + NaN +(1 row) + +SELECT power(float8 '144', float8 'NaN'); + power +------- + NaN +(1 row) + +SELECT power(float8 'NaN', float8 'NaN'); + power +------- + NaN +(1 row) + +SELECT power(float8 '1', float8 'NaN'); + power +------- + 1 +(1 row) + +SELECT power(float8 'NaN', float8 '0'); + power +------- + 1 +(1 row) + -- take exp of ln(f.f1) SELECT '' AS three, f.f1, exp(ln(f.f1)) AS exp_ln_f1 FROM FLOAT8_TBL f diff --git a/src/test/regress/expected/float8-small-is-zero_1.out b/src/test/regress/expected/float8-small-is-zero_1.out index 530842e102..e9487cffa6 100644 --- a/src/test/regress/expected/float8-small-is-zero_1.out +++ b/src/test/regress/expected/float8-small-is-zero_1.out @@ -344,6 +344,36 @@ SELECT power(float8 '144', float8 '0.5'); 12 (1 row) +SELECT power(float8 'NaN', float8 '0.5'); + power +------- + NaN +(1 row) + +SELECT power(float8 '144', float8 'NaN'); + power +------- + NaN +(1 row) + +SELECT power(float8 'NaN', float8 'NaN'); + power +------- + NaN +(1 row) + +SELECT power(float8 '1', float8 'NaN'); + power +------- + 1 +(1 row) + +SELECT power(float8 'NaN', float8 '0'); + power +------- + 1 +(1 row) + -- take exp of ln(f.f1) SELECT '' AS three, f.f1, exp(ln(f.f1)) AS exp_ln_f1 FROM FLOAT8_TBL f diff --git a/src/test/regress/expected/float8.out b/src/test/regress/expected/float8.out index 6221538af5..1bf225ca2b 100644 --- a/src/test/regress/expected/float8.out +++ b/src/test/regress/expected/float8.out @@ -340,6 +340,36 @@ SELECT power(float8 '144', float8 '0.5'); 12 (1 row) +SELECT power(float8 'NaN', float8 '0.5'); + power +------- + NaN +(1 row) + +SELECT power(float8 '144', float8 'NaN'); + power +------- + NaN +(1 row) + +SELECT power(float8 'NaN', float8 'NaN'); + power +------- + NaN +(1 row) + +SELECT power(float8 '1', float8 'NaN'); + power +------- + 1 +(1 row) + +SELECT power(float8 'NaN', float8 '0'); + power +------- + 1 +(1 row) + -- take exp of ln(f.f1) SELECT '' AS three, f.f1, exp(ln(f.f1)) AS exp_ln_f1 FROM FLOAT8_TBL f diff --git a/src/test/regress/sql/float8.sql b/src/test/regress/sql/float8.sql index 92a574ab7b..2b2e175c6d 100644 --- a/src/test/regress/sql/float8.sql +++ b/src/test/regress/sql/float8.sql @@ -108,6 +108,11 @@ SELECT '' AS three, f.f1, |/f.f1 AS sqrt_f1 -- power SELECT power(float8 '144', float8 '0.5'); +SELECT power(float8 'NaN', float8 '0.5'); +SELECT power(float8 '144', float8 'NaN'); +SELECT power(float8 'NaN', float8 'NaN'); +SELECT power(float8 '1', float8 'NaN'); +SELECT power(float8 'NaN', float8 '0'); -- take exp of ln(f.f1) SELECT '' AS three, f.f1, exp(ln(f.f1)) AS exp_ln_f1