From fac83dbd6fe1ac3d4125bfa39f287f95bffe6cda Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Wed, 4 Nov 2020 18:11:15 -0500 Subject: [PATCH] Remove underflow error in float division with infinite divisor. float4_div and float8_div correctly produced zero for zero divided by infinity, but threw an underflow error for nonzero finite values divided by infinity. This seems wrong; at the very least it's inconsistent with the behavior recently implemented for numeric infinities. Remove the error and allow zero to be returned. This patch also removes a useless isinf() test from the overflow checks in these functions (non-Inf divided by Inf can't produce Inf). Extracted from a larger patch; this seems significant outside the context of geometric operators, so it deserves its own commit. Kyotaro Horiguchi Discussion: https://postgr.es/m/CAGf+fX70rWFOk5cd00uMfa__0yP+vtQg5ck7c2Onb-Yczp0URA@mail.gmail.com --- src/include/utils/float.h | 8 ++++---- src/test/regress/expected/float4-misrounded-input.out | 6 ++++++ src/test/regress/expected/float4.out | 6 ++++++ src/test/regress/expected/float8.out | 6 ++++++ src/test/regress/sql/float4.sql | 1 + src/test/regress/sql/float8.sql | 1 + 6 files changed, 24 insertions(+), 4 deletions(-) diff --git a/src/include/utils/float.h b/src/include/utils/float.h index e2aae8ef177..79bf8daca80 100644 --- a/src/include/utils/float.h +++ b/src/include/utils/float.h @@ -225,9 +225,9 @@ float4_div(const float4 val1, const float4 val2) if (unlikely(val2 == 0.0f) && !isnan(val1)) float_zero_divide_error(); result = val1 / val2; - if (unlikely(isinf(result)) && !isinf(val1) && !isinf(val2)) + if (unlikely(isinf(result)) && !isinf(val1)) float_overflow_error(); - if (unlikely(result == 0.0f) && val1 != 0.0f) + if (unlikely(result == 0.0f) && val1 != 0.0f && !isinf(val2)) float_underflow_error(); return result; @@ -241,9 +241,9 @@ float8_div(const float8 val1, const float8 val2) if (unlikely(val2 == 0.0) && !isnan(val1)) float_zero_divide_error(); result = val1 / val2; - if (unlikely(isinf(result)) && !isinf(val1) && !isinf(val2)) + if (unlikely(isinf(result)) && !isinf(val1)) float_overflow_error(); - if (unlikely(result == 0.0) && val1 != 0.0) + if (unlikely(result == 0.0) && val1 != 0.0 && !isinf(val2)) float_underflow_error(); return result; diff --git a/src/test/regress/expected/float4-misrounded-input.out b/src/test/regress/expected/float4-misrounded-input.out index 38b847a1adb..7b4964e1799 100644 --- a/src/test/regress/expected/float4-misrounded-input.out +++ b/src/test/regress/expected/float4-misrounded-input.out @@ -137,6 +137,12 @@ SELECT 'Infinity'::float4 / 'Infinity'::float4; NaN (1 row) +SELECT '42'::float4 / 'Infinity'::float4; + ?column? +---------- + 0 +(1 row) + SELECT 'nan'::float4 / 'nan'::float4; ?column? ---------- diff --git a/src/test/regress/expected/float4.out b/src/test/regress/expected/float4.out index 310402b6ee2..dde8c343ce4 100644 --- a/src/test/regress/expected/float4.out +++ b/src/test/regress/expected/float4.out @@ -137,6 +137,12 @@ SELECT 'Infinity'::float4 / 'Infinity'::float4; NaN (1 row) +SELECT '42'::float4 / 'Infinity'::float4; + ?column? +---------- + 0 +(1 row) + SELECT 'nan'::float4 / 'nan'::float4; ?column? ---------- diff --git a/src/test/regress/expected/float8.out b/src/test/regress/expected/float8.out index 2304b579d2b..63da7338937 100644 --- a/src/test/regress/expected/float8.out +++ b/src/test/regress/expected/float8.out @@ -120,6 +120,12 @@ SELECT 'Infinity'::float8 / 'Infinity'::float8; NaN (1 row) +SELECT '42'::float8 / 'Infinity'::float8; + ?column? +---------- + 0 +(1 row) + SELECT 'nan'::float8 / 'nan'::float8; ?column? ---------- diff --git a/src/test/regress/sql/float4.sql b/src/test/regress/sql/float4.sql index 1fcf823c21b..14e54714826 100644 --- a/src/test/regress/sql/float4.sql +++ b/src/test/regress/sql/float4.sql @@ -49,6 +49,7 @@ SELECT ' INFINITY x'::float4; SELECT 'Infinity'::float4 + 100.0; SELECT 'Infinity'::float4 / 'Infinity'::float4; +SELECT '42'::float4 / 'Infinity'::float4; SELECT 'nan'::float4 / 'nan'::float4; SELECT 'nan'::float4 / '0'::float4; SELECT 'nan'::numeric::float4; diff --git a/src/test/regress/sql/float8.sql b/src/test/regress/sql/float8.sql index f103871cdb2..7e817198533 100644 --- a/src/test/regress/sql/float8.sql +++ b/src/test/regress/sql/float8.sql @@ -42,6 +42,7 @@ SELECT ' INFINITY x'::float8; SELECT 'Infinity'::float8 + 100.0; SELECT 'Infinity'::float8 / 'Infinity'::float8; +SELECT '42'::float8 / 'Infinity'::float8; SELECT 'nan'::float8 / 'nan'::float8; SELECT 'nan'::float8 / '0'::float8; SELECT 'nan'::numeric::float8;