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MDEV-38670 Unary minus on empty string returns -0 #4632

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MDEV-38670 Unary minus on empty string returns -0 #4632

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96 changes: 96 additions & 0 deletions mysql-test/main/func_math.result
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Original file line number Diff line number Diff line change
Expand Up @@ -3739,3 +3739,99 @@ cast(1 as unsigned) - cast(2 as unsigned)
-1
set sql_mode=default;
# End of 10.5 tests
#
# MDEV-38670 Minus string is converted to -0
#
# Testing arithmetic operations with signed zero
SELECT -0.0 + 0.0;
-0.0 + 0.0
0.0
SELECT 0.0 + -0.0;
0.0 + -0.0
0.0
SELECT -0.0 + -0.0;
-0.0 + -0.0
0.0
SELECT -0.0 - 0.0;
-0.0 - 0.0
0.0
SELECT 0.0 - '';
0.0 - ''
0
Warnings:
Warning 1292 Truncated incorrect DOUBLE value: ''
SELECT -0.0;
-0.0
0.0
SELECT 0.0 * -1.0;
0.0 * -1.0
0.00
SELECT 0e0*-1e0;
0e0*-1e0
0
SELECT -'';
-''
0
Warnings:
Warning 1292 Truncated incorrect DOUBLE value: ''
SELECT ABS(-0.0);
ABS(-0.0)
0.0
SELECT -0.0 % 1.0;
-0.0 % 1.0
0.0
# Testing comparison functions with signed zero
SELECT CASE WHEN -0.0=0.0 THEN 1.0 ELSE 0.0 END;
CASE WHEN -0.0=0.0 THEN 1.0 ELSE 0.0 END
1.0
SELECT CASE WHEN -''=0.0 THEN 1.0 ELSE 0.0 END;
CASE WHEN -''=0.0 THEN 1.0 ELSE 0.0 END
1.0
Warnings:
Warning 1292 Truncated incorrect DOUBLE value: ''
SELECT CASE WHEN 0e0*-1e0=0.0 THEN 1.0 ELSE 0.0 END;
CASE WHEN 0e0*-1e0=0.0 THEN 1.0 ELSE 0.0 END
1.0
# Testing with table data
CREATE TABLE t1 (a DOUBLE, b DOUBLE);
INSERT INTO t1 VALUES
(0.0, 1.0),
(-0.0, 1.0),
(1.0, 0.0),
(1.0, -0.0),
(0.0, 0.0),
(-0.0, -0.0);
SELECT a, b, a + b AS sum_ab, a - b AS diff_ab, a * b AS mul_ab FROM t1;
a b sum_ab diff_ab mul_ab
0 1 1 -1 0
0 1 1 -1 0
1 0 1 1 0
1 0 1 1 0
0 0 0 0 0
0 0 0 0 0
SELECT a, b, IFNULL(a, b) AS ifnull_ab, NULLIF(a, b) AS nullif_ab FROM t1;
a b ifnull_ab nullif_ab
0 1 0 0
0 1 0 0
1 0 1 1
1 0 1 1
0 0 0 NULL
0 0 0 NULL
SELECT a, b, CASE WHEN a > 0 THEN a ELSE b END AS case_ab FROM t1;
a b case_ab
0 1 1
0 1 1
1 0 1
1 0 1
0 0 0
0 0 0
SELECT a, b, COALESCE(a, b) AS coalesce_ab FROM t1;
a b coalesce_ab
0 1 0
0 1 0
1 0 1
1 0 1
0 0 0
0 0 0
DROP TABLE t1;
# End of 13 tests
54 changes: 54 additions & 0 deletions mysql-test/main/func_math.test
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Expand Up @@ -1998,3 +1998,57 @@ select cast(1 as unsigned) - cast(2 as unsigned);
set sql_mode=default;

--echo # End of 10.5 tests
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@gkodinov gkodinov Feb 12, 2026

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It is customary to end a test file with a version test end echo command. Please add one for the target version: 13 in your case I believe, unless the final reviewer requests otherwise.


--echo #
--echo # MDEV-38670 Minus string is converted to -0
--echo #

--source include/have_innodb.inc

# Test arithmetic operations
--echo # Testing arithmetic operations with signed zero

SELECT -0.0 + 0.0;
SELECT 0.0 + -0.0;
SELECT -0.0 + -0.0;

SELECT -0.0 - 0.0;
SELECT 0.0 - '';

SELECT -0.0;
SELECT 0.0 * -1.0;
SELECT 0e0*-1e0;
SELECT -'';


SELECT ABS(-0.0);

SELECT -0.0 % 1.0;

# Test comparison functions
--echo # Testing comparison functions with signed zero

SELECT CASE WHEN -0.0=0.0 THEN 1.0 ELSE 0.0 END;
SELECT CASE WHEN -''=0.0 THEN 1.0 ELSE 0.0 END;
SELECT CASE WHEN 0e0*-1e0=0.0 THEN 1.0 ELSE 0.0 END;


# Test with table data
--echo # Testing with table data

CREATE TABLE t1 (a DOUBLE, b DOUBLE);
INSERT INTO t1 VALUES
(0.0, 1.0),
(-0.0, 1.0),
(1.0, 0.0),
(1.0, -0.0),
(0.0, 0.0),
(-0.0, -0.0);

SELECT a, b, a + b AS sum_ab, a - b AS diff_ab, a * b AS mul_ab FROM t1;
SELECT a, b, IFNULL(a, b) AS ifnull_ab, NULLIF(a, b) AS nullif_ab FROM t1;
SELECT a, b, CASE WHEN a > 0 THEN a ELSE b END AS case_ab FROM t1;
SELECT a, b, COALESCE(a, b) AS coalesce_ab FROM t1;

DROP TABLE t1;
--echo # End of 13 tests
8 changes: 4 additions & 4 deletions sql/item_cmpfunc.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -2496,7 +2496,7 @@ Item_func_ifnull::real_op()
value= args[1]->val_real();
if ((null_value=args[1]->null_value))
return 0.0;
return value;
return normalize_signed_zero(value);
}

longlong
Expand Down Expand Up @@ -3036,7 +3036,7 @@ Item_func_nullif::real_op()
}
value= args[2]->val_real();
null_value= args[2]->null_value;
return value;
return normalize_signed_zero(value);
}

longlong
Expand Down Expand Up @@ -3250,7 +3250,7 @@ double Item_func_case::real_op()
}
res= item->val_real();
null_value=item->null_value;
return res;
return normalize_signed_zero(res);
}


Expand Down Expand Up @@ -3649,7 +3649,7 @@ double Item_func_coalesce::real_op()
{
double res= args[i]->val_real();
if (!args[i]->null_value)
return res;
return normalize_signed_zero(res);
}
null_value=1;
return 0;
Expand Down
20 changes: 10 additions & 10 deletions sql/item_func.cc
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Expand Up @@ -1172,7 +1172,7 @@ double Item_func_plus::real_op()
double value= args[0]->val_real() + args[1]->val_real();
if ((null_value=args[0]->null_value || args[1]->null_value))
return 0.0;
return check_float_overflow(value);
return normalize_signed_zero(check_float_overflow(value));
}

#if defined(__powerpc64__) && GCC_VERSION >= 6003 && GCC_VERSION <= 10002
Expand Down Expand Up @@ -1338,7 +1338,7 @@ double Item_func_minus::real_op()
double value= args[0]->val_real() - args[1]->val_real();
if ((null_value=args[0]->null_value || args[1]->null_value))
return 0.0;
return check_float_overflow(value);
return normalize_signed_zero(check_float_overflow(value));
}


Expand Down Expand Up @@ -1440,7 +1440,7 @@ double Item_func_mul::real_op()
double value= args[0]->val_real() * args[1]->val_real();
if ((null_value=args[0]->null_value || args[1]->null_value))
return 0.0;
return check_float_overflow(value);
return normalize_signed_zero(check_float_overflow(value));
}


Expand Down Expand Up @@ -1522,7 +1522,7 @@ double Item_func_div::real_op()
signal_divide_by_null();
return 0.0;
}
return check_float_overflow(value/val2);
return normalize_signed_zero(check_float_overflow(value/val2));
}


Expand Down Expand Up @@ -1712,7 +1712,7 @@ double Item_func_mod::real_op()
signal_divide_by_null();
return 0.0;
}
return fmod(value,val2);
return normalize_signed_zero(fmod(value,val2));
}


Expand Down Expand Up @@ -1825,7 +1825,7 @@ double Item_func_neg::real_op()
{
double value= args[0]->val_real();
null_value= args[0]->null_value;
return -value;
return normalize_signed_zero(-value);
}


Expand Down Expand Up @@ -1931,7 +1931,7 @@ double Item_func_abs::real_op()
{
double value= args[0]->val_real();
null_value= args[0]->null_value;
return fabs(value);
return normalize_signed_zero(fabs(value));
}


Expand Down Expand Up @@ -2409,7 +2409,7 @@ double Item_func_ceiling::real_op()
*/
volatile double value= args[0]->val_real();
null_value= args[0]->null_value;
return ceil(value);
return normalize_signed_zero(ceil(value));
}


Expand Down Expand Up @@ -2473,7 +2473,7 @@ double Item_func_floor::real_op()
*/
volatile double value= args[0]->val_real();
null_value= args[0]->null_value;
return floor(value);
return normalize_signed_zero(floor(value));
}


Expand Down Expand Up @@ -2741,7 +2741,7 @@ double Item_func_round::real_op()
{
longlong dec= args[1]->val_int();
if (!(null_value= args[1]->null_value))
return my_double_round(value, dec, args[1]->unsigned_flag, truncate);
return normalize_signed_zero(my_double_round(value, dec, args[1]->unsigned_flag, truncate));
}
return 0.0;
}
Expand Down
5 changes: 5 additions & 0 deletions sql/item_func.h
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Expand Up @@ -285,6 +285,10 @@ class Item_func :public Item_func_or_sum
print(&str, QT_NO_DATA_EXPANSION);
my_error(ER_DATA_OUT_OF_RANGE, MYF(0), type_name, str.c_ptr_safe());
}
inline double normalize_signed_zero(double value)
{
return value == 0.0 ? 0.0 : value; // Converts -0.0 to +0.0
}
inline double raise_float_overflow()
{
raise_numeric_overflow("DOUBLE");
Expand All @@ -308,6 +312,7 @@ class Item_func :public Item_func_or_sum
{
return std::isfinite(value) ? value : raise_float_overflow();
}

/**
Throw an error if the input BIGINT value represented by the
(longlong value, bool unsigned flag) pair cannot be returned by the
Expand Down