From 4d864de486d63b50b1ba74330021504d2c674c23 Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Sun, 29 Apr 2018 15:21:44 -0400 Subject: [PATCH] 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 --- src/backend/utils/adt/float.c | 7 +++-- .../float8-exp-three-digits-win32.out | 30 +++++++++++++++++++ .../regress/expected/float8-small-is-zero.out | 30 +++++++++++++++++++ .../expected/float8-small-is-zero_1.out | 30 +++++++++++++++++++ src/test/regress/expected/float8.out | 30 +++++++++++++++++++ src/test/regress/sql/float8.sql | 5 ++++ 6 files changed, 129 insertions(+), 3 deletions(-) diff --git a/src/backend/utils/adt/float.c b/src/backend/utils/adt/float.c index 18b3b949ac..9f4afaa08b 100644 --- a/src/backend/utils/adt/float.c +++ b/src/backend/utils/adt/float.c @@ -1479,14 +1479,15 @@ 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 7e1153308f..3fe50b4bf0 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 26b8378150..46adbe1c4b 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 cea27908eb..f215eede10 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 20c985e5df..7159e78d4a 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 215e7a4784..5510fe9d34 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