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Bug #20569 Garbage in DECIMAL results from some mathematical functions 

Adding decimal "digits" in multiplication resulted in signed overflow and
producing wrong results.

  Fixed by using large enough buffers and intermediary result types :
dec2 (currently longlong) to hold result of adding decimal "digits" 
(currently int32). 


mysql-test/r/select.result:
  Bug #20569 Garbage in DECIMAL results from some mathematical functions
    * test suite for the bug
mysql-test/t/select.test:
  Bug #20569 Garbage in DECIMAL results from some mathematical functions
    * test suite for the bug
strings/decimal.c:
  Bug #20569 Garbage in DECIMAL results from some mathematical functions
    * fixed the overflow in adding decimal "digits"
pull/374/head
unknown 20 years ago
parent
3cf92fb7d6
commit
8e354677a8
3 changed files with 18 additions and 3 deletions
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  1. 3
      mysql-test/r/select.result
  2. 5
      mysql-test/t/select.test
  3. 13
      strings/decimal.c

3
mysql-test/r/select.result
View File

@ -3395,3 +3395,6 @@ a t1.b + 0 t1.c + 0 a t2.b + 0 c d
1 0 1 1 0 1 NULL
2 0 1 NULL NULL NULL NULL
drop table t1,t2;
SELECT 0.9888889889 * 1.011111411911;
0.9888889889 * 1.011111411911
0.9998769417899202067879

5
mysql-test/t/select.test
View File

@ -2901,3 +2901,8 @@ from t1 left outer join t2 on t1.a = t2.c and t2.b <> 1
where t1.b <> 1 order by t1.a;
drop table t1,t2;
#
# Bug #20569: Garbage in DECIMAL results from some mathematical functions
#
SELECT 0.9888889889 * 1.011111411911;

13
strings/decimal.c
View File

@ -170,6 +170,7 @@ static const dec1 frac_max[DIG_PER_DEC1-1]={
#define ADD(to, from1, from2, carry) /* assume carry <= 1 */ \
do \
{ \
DBUG_ASSERT((carry) <= 1); \
dec1 a=(from1)+(from2)+(carry); \
if (((carry)= a >= DIG_BASE)) /* no division here! */ \
a-=DIG_BASE; \
@ -179,7 +180,7 @@ static const dec1 frac_max[DIG_PER_DEC1-1]={
#define ADD2(to, from1, from2, carry) \
do \
{ \
dec1 a=(from1)+(from2)+(carry); \
dec2 a=((dec2)(from1))+(from2)+(carry); \
if (((carry)= a >= DIG_BASE)) \
a-=DIG_BASE; \
if (unlikely(a >= DIG_BASE)) \
@ -187,7 +188,7 @@ static const dec1 frac_max[DIG_PER_DEC1-1]={
a-=DIG_BASE; \
carry++; \
} \
(to)=a; \
(to)=(dec1) a; \
} while(0)
#define SUB(to, from1, from2, carry) /* to=from1-from2 */ \
@ -1998,7 +1999,13 @@ int decimal_mul(decimal_t *from1, decimal_t *from2, decimal_t *to)
ADD2(*buf0, *buf0, lo, carry);
carry+=hi;
}
for (; carry; buf0--)
if (carry)
{
if (buf0 < to->buf)
return E_DEC_OVERFLOW;
ADD2(*buf0, *buf0, 0, carry);
}
for (buf0--; carry; buf0--)
{
if (buf0 < to->buf)
return E_DEC_OVERFLOW;

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