| Bug #78641 | cast of too big HEX literal to BIGINT UNSIGNED: bad result and no warning | ||
|---|---|---|---|
| Submitted: | 30 Sep 2015 8:47 | Modified: | 15 Oct 2015 14:01 |
| Reporter: | Guilhem Bichot | Email Updates: | |
| Status: | Closed | Impact on me: | |
| Category: | MySQL Server: Data Types | Severity: | S3 (Non-critical) |
| Version: | 5.7.8, 5.7.10, 5.6.28 | OS: | Any |
| Assigned to: | CPU Architecture: | Any | |
[30 Sep 2015 8:49]
Guilhem Bichot
select 0x9999999999999999999999999999999999999999999 + 0; | 11068046444225730000 | must also be fixed.
[30 Sep 2015 8:52]
Guilhem Bichot
moreover 0x9999999999999999999999999999999999999999999 + 0 is of type DOUBLE, I rather expected it would be BIGINT, as the doc says "In numeric contexts, hexadecimal values act like integers (64-bit precision)".
[30 Sep 2015 8:54]
Umesh Shastry
Hello Guilhem, Thank you for the report and test case. Thanks, Umesh
[12 Oct 2015 8:30]
Guilhem Bichot
the "type DOUBLE" issue above is the cause of http://bugs.mysql.com/bug.php?id=49530 which has been marked as duplicate.
[15 Oct 2015 14:01]
Paul Dubois
Noted in 5.7.10, 5.8.0 changelogs. Casting large hexadecimal values could produce an incorrect result and no truncation warning.
Description: This is correct (truncation to max value of type *with warning*): select convert(9999999999999999999999999999999999999999999,unsigned); | 18446744073709551615 | Warning (Code 1292): Truncated incorrect DECIMAL value: '9999999999999999999999999999999999999999999' So is this: select convert('9999999999999999999999999999999999999999999',unsigned); | 18446744073709551615 | Warning (Code 1292): Truncated incorrect INTEGER value: '9999999999999999999999999999999999999999999' This is incorrect: select convert(0x9999999999999999999999999999999999999999999,unsigned); | 11068046444225730969 | Only some parts of the hex string are converted, and there's no warning. How to repeat: select convert(0x9999999999999999999999999999999999999999999,unsigned); Other examples to fix: select 9999999999999999999999999999999999999999999 | 0; gives max value + warning (good), but select 0x9999999999999999999999999999999999999999999 | 0; gives 11068046444225730969 and no warning (bad). Suggested fix: Here: longlong Item_hex_string::val_int() { // following assert is redundant, because fixed=1 assigned in constructor DBUG_ASSERT(fixed == 1); char *end=(char*) str_value.ptr()+str_value.length(), *ptr= end - min<size_t>(str_value.length(), sizeof(longlong)); it just takes the last 8 bytes; if by doing this it ignores any non-zero byte elsewhere in the string, it should emit a warning and return the max possible bigint value.