| Bug #25251 | libmysql.c:4322: setup_one_fetch_function: Assertion `param->buffer_length != 0' | ||
|---|---|---|---|
| Submitted: | 22 Dec 2006 18:16 | Modified: | 18 Feb 2008 18:54 |
| Reporter: | Philip Stoev | Email Updates: | |
| Status: | Closed | Impact on me: | |
| Category: | MySQL Server: C API (client library) | Severity: | S3 (Non-critical) |
| Version: | 5.0.27 | OS: | Linux (Linux; FreeBsd ) |
| Assigned to: | Andrey Hristov | CPU Architecture: | Any |
| Tags: | qc | ||
[22 Dec 2006 21:03]
Philip Stoev
server_side_prepare must be enabled and working for this bug to manifest itself via DBI (though it does not look like a bug of DBD::mysql). Please make sure you have the latest DBD::mysql and that DBI tracing shows that dbd_describe() was called indeede.
[26 Dec 2006 21:38]
Sveta Smirnova
Thank you for the report. Verified as described using DBD-4.00 and last BK MySQL server. With simple C test program error is not repeatable.
[18 Feb 2008 18:54]
Andrey Hristov
This bug can't be reproduced anymore. In the libmysql sources the assert is missing.
[18 Feb 2008 18:54]
Andrey Hristov
The test cases work as expected.
Description: Hello, The following statements will not execute properly from DBI: SELECT ''; SELECT SUBSTR('a', 2); SELECT CONCAT_WS('',''); SELECT REPEAT(-1,'a'); DBI fails with: perl: libmysql.c:4322: setup_one_fetch_function: Assertion `param->buffer_length != 0' failed. How to repeat: my $sth = $dbh->prepare("SELECT ''"); $sth->execute(); $dbh->do() does not trigger this behavoir (possibly because the new-style MySQL binary protocol does not kick in). Suggested fix: What happens is that DBD's dbd_describe() calls mysql_fetch_fields() which returns a fields[0].length of 0. This is then passed to mysql_stmt_bind_result which calls setup_one_fetch_function() which causes the assertion since buffer_length can not be zero if type is MYSQL_TYPE_STRING. It appears that the length is zero because all those functions in those special cases return &my_empty_string which probably has a length of zero which gets propagated all the way up to the caller. IF it is OK to have a buffer MYSQL_BIND structure with buffer_length == 0 (that is, if it is trailing \0 safe), then the assertion should be removed.