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Commit61b200e

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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 doesreturn NaN, but it also sets errno = EDOM, confusing our code thatattempts to work around shortcomings of other platforms. Hence, addguard 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 appearsin older MSVC releases, too) so back-patch to all supported branches.Dang Minh Huong, reviewed by David RowleyDiscussion:https://postgr.es/m/75DB81BEEA95B445AE6D576A0A5C9E936A73E741@BPXM05GP.gisp.nec.co.jp
1 parent85475af commit61b200e

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6 files changed

+129
-3
lines changed

6 files changed

+129
-3
lines changed

‎src/backend/utils/adt/float.c

Lines changed: 4 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -1566,14 +1566,15 @@ dpow(PG_FUNCTION_ARGS)
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* pow() sets errno only on some platforms, depending on whether it
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* follows _IEEE_, _POSIX_, _XOPEN_, or _SVID_, so we try to avoid using
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* errno. However, some platform/CPU combinations return errno == EDOM
1569-
* and result ==Nan for negative arg1 and very large arg2 (they must be
1569+
* and result ==NaN for negative arg1 and very large arg2 (they must be
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* using something different from our floor() test to decide it's
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* invalid). Other platforms (HPPA) return errno == ERANGE and a large
1572-
* (HUGE_VAL) but finite result to signal overflow.
1572+
* (HUGE_VAL) but finite result to signal overflow. Also, some versions
1573+
* of MSVC return errno == EDOM and result == NaN for NaN inputs.
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*/
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errno=0;
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result=pow(arg1,arg2);
1576-
if (errno==EDOM&&isnan(result))
1577+
if (errno==EDOM&&isnan(result)&& !isnan(arg1)&& !isnan(arg2))
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{
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if ((fabs(arg1)>1&&arg2 >=0)|| (fabs(arg1)<1&&arg2<0))
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/* The sign of Inf is not significant in this case. */

‎src/test/regress/expected/float8-exp-three-digits-win32.out

Lines changed: 30 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -340,6 +340,36 @@ SELECT power(float8 '144', float8 '0.5');
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(1 row)
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SELECT power(float8 'NaN', float8 '0.5');
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power
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-------
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NaN
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(1 row)
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SELECT power(float8 '144', float8 'NaN');
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power
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-------
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NaN
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(1 row)
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SELECT power(float8 'NaN', float8 'NaN');
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power
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-------
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NaN
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(1 row)
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SELECT power(float8 '1', float8 'NaN');
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power
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-------
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1
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(1 row)
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SELECT power(float8 'NaN', float8 '0');
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power
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-------
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1
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(1 row)
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343373
-- take exp of ln(f.f1)
344374
SELECT '' AS three, f.f1, exp(ln(f.f1)) AS exp_ln_f1
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FROM FLOAT8_TBL f

‎src/test/regress/expected/float8-small-is-zero.out

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Original file line numberDiff line numberDiff line change
@@ -344,6 +344,36 @@ SELECT power(float8 '144', float8 '0.5');
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12
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(1 row)
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SELECT power(float8 'NaN', float8 '0.5');
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power
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-------
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NaN
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(1 row)
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SELECT power(float8 '144', float8 'NaN');
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power
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-------
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NaN
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(1 row)
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SELECT power(float8 'NaN', float8 'NaN');
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power
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-------
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NaN
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(1 row)
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SELECT power(float8 '1', float8 'NaN');
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power
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-------
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1
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(1 row)
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SELECT power(float8 'NaN', float8 '0');
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power
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-------
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1
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(1 row)
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347377
-- take exp of ln(f.f1)
348378
SELECT '' AS three, f.f1, exp(ln(f.f1)) AS exp_ln_f1
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FROM FLOAT8_TBL f

‎src/test/regress/expected/float8-small-is-zero_1.out

Lines changed: 30 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -344,6 +344,36 @@ SELECT power(float8 '144', float8 '0.5');
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12
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(1 row)
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SELECT power(float8 'NaN', float8 '0.5');
348+
power
349+
-------
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NaN
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(1 row)
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SELECT power(float8 '144', float8 'NaN');
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power
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-------
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NaN
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(1 row)
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SELECT power(float8 'NaN', float8 'NaN');
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power
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-------
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NaN
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(1 row)
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SELECT power(float8 '1', float8 'NaN');
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power
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-------
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1
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(1 row)
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SELECT power(float8 'NaN', float8 '0');
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power
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-------
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1
375+
(1 row)
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347377
-- take exp of ln(f.f1)
348378
SELECT '' AS three, f.f1, exp(ln(f.f1)) AS exp_ln_f1
349379
FROM FLOAT8_TBL f

‎src/test/regress/expected/float8.out

Lines changed: 30 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -340,6 +340,36 @@ SELECT power(float8 '144', float8 '0.5');
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12
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(1 row)
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343+
SELECT power(float8 'NaN', float8 '0.5');
344+
power
345+
-------
346+
NaN
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(1 row)
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SELECT power(float8 '144', float8 'NaN');
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power
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-------
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NaN
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(1 row)
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355+
SELECT power(float8 'NaN', float8 'NaN');
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power
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-------
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NaN
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(1 row)
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SELECT power(float8 '1', float8 'NaN');
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power
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-------
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1
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(1 row)
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SELECT power(float8 'NaN', float8 '0');
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power
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-------
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1
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(1 row)
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343373
-- take exp of ln(f.f1)
344374
SELECT '' AS three, f.f1, exp(ln(f.f1)) AS exp_ln_f1
345375
FROM FLOAT8_TBL f

‎src/test/regress/sql/float8.sql

Lines changed: 5 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -108,6 +108,11 @@ SELECT '' AS three, f.f1, |/f.f1 AS sqrt_f1
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-- power
110110
SELECT power(float8'144', float8'0.5');
111+
SELECT power(float8'NaN', float8'0.5');
112+
SELECT power(float8'144', float8'NaN');
113+
SELECT power(float8'NaN', float8'NaN');
114+
SELECT power(float8'1', float8'NaN');
115+
SELECT power(float8'NaN', float8'0');
111116

112117
-- take exp of ln(f.f1)
113118
SELECT''AS three,f.f1, exp(ln(f.f1))AS exp_ln_f1

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