(just for folks getting started with MySQL++ and seeing failures in the
examples)
There is a known issue with Query::str() adding a null byte, which is
apparently documented behavior to be fixed in the next major release.
Query::preview() uses str().
This affects the dbinfo example where queries are printed out before
being used:
cout << "Query: " << query.preview() << endl;
If you remove the query.preview()'s from examples/dbinfo.cpp, the
example works as expected.
This causes the following error (Linux example):
-----------------------------------
$ ./dbinfo localhost user1 passwd1
MySQL version: 5.0.27
---------------------------
Query: show databases
Query error: You have an error in your SQL syntax; check the manual
that corresponds to your MySQL server version for the right syntax
to use near '' at line 1
-----------------------------------
Analysis ...
If you debug the code, you'll see that the string which gets passed to
mysql_real_query() has two NULL bytes at the end.
(gdb) s
mysqlpp::Query::store (this=0xbfb42844, str=0x807067c "show
databases", len=16) at ./lib/query.cpp:436
436 if (lock()) {
(gdb) p str[14]
$1 = 0 '\0'
(gdb) p str[15]
$2 = 0 '\0'
(gdb)
If you change the length of "str" (via gdb using "p len=15" in the
example above), the syntax error goes away. One null byte is ok, two
apparently is interpreted as a second, empty "" statement by
mysql_real_query().
The same issue affects the custom2, custom3, fieldinf1, and multiquery
examples. custom5 works because the preview() is done after the queries.
I could patch Query::store() to trim extra trailing null bytes as
mysql_real_query() clearly interprets these as empty queries, which is
consistent with the MySQL documentation. I've had about 5 minutes with
the code base, so I may be missing something obvious (and documented).
Cheers ...
Ed
