Hello, I'd just like to check if I'm not missing something obvious here: I thought it was perfectly fine to execute the same statement more than once with different parameter values, e.g. do something like this:
int f;
statement st = (sql.prepare << "insert into t(f) values(:f)", use(f));
for (f = 0; f < 10; f++)
st.execute(true);
And, in fact, this does work fine in the sense that the expected values are
inserted in the database.
However currently if any values requiring memory allocation are used, e.g.
strings, but also dates and even long longs in some backends, there are
also plenty of memory leaks, at least in the ODBC backend where I
definitely see them, but also, apparently, in some of the other ones from
examining the code. They happen because the code in
whatever_use_type_backend::pre_use() happily overwrites buf_ with the
new allocation without freeing the old one, and if execute(true) is called
more than once, pre_use() is also called more than once.
So the first question is whether this is really allowed or is this a
misuse of the SOCI API. I hope it it legal and then the memory leaks need
to be fixed. AFAICS there are 2 ways of doing it: either do as MySQL,
PostgreSQL and SQLite backends do and just call clean_up() in post_use(),
or be a bit smarter and reallocate the buffer if it's already allocated
instead of always allocating the new one. This would, of course, mean
switching to realloc() from new[] currently being used, but could be
noticeably more efficient when a lot of execute() calls are done in a loop.
What do you think?
VZ
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