[Tarantool-patches] [PATCH] Fix wrong make_scoped_guard usage
Nikita Pettik
korablev at tarantool.org
Thu Jul 9 13:24:58 MSK 2020
On 08 Jul 15:07, Aleksandr Lyapunov wrote:
> The common pitfall of using a lambda is wrong type of capture -
> by value instead of by reference. The simple example is:
> struct sequence_def *new_def = NULL;
> auto def_guard = make_scoped_guard([=] { free(new_def); });
> // initialize new_def
> The problem is that the lambda captures pointer by value, that
> is NULL and will remain NULL in the lambda while new_def is
> successfully initialized in function scope.
>
> The patch fixes the problem above and a couple of similar mistakes.
> ---
Agree with Cyrill that we could simply use &. Anyway LGTM,
let's push this patch.
> src/box/alter.cc | 4 ++--
> src/main.cc | 2 +-
> 2 files changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/src/box/alter.cc b/src/box/alter.cc
> index bb42548..3109fb4 100644
> --- a/src/box/alter.cc
> +++ b/src/box/alter.cc
> @@ -3560,7 +3560,7 @@ on_replace_dd_func(struct trigger * /* trigger */, void *event)
> * definition to support upgrade script.
> */
> struct func_def *old_def = NULL, *new_def = NULL;
> - auto guard = make_scoped_guard([=] {
> + auto guard = make_scoped_guard([&old_def, &new_def] {
> free(old_def);
> free(new_def);
> });
> @@ -4431,7 +4431,7 @@ on_replace_dd_sequence(struct trigger * /* trigger */, void *event)
> struct tuple *new_tuple = stmt->new_tuple;
>
> struct sequence_def *new_def = NULL;
> - auto def_guard = make_scoped_guard([=] { free(new_def); });
> + auto def_guard = make_scoped_guard([&new_def] { free(new_def); });
>
> struct sequence *seq;
> if (old_tuple == NULL && new_tuple != NULL) { /* INSERT */
> diff --git a/src/main.cc b/src/main.cc
> index 2c96391..e622042 100644
> --- a/src/main.cc
> +++ b/src/main.cc
> @@ -729,7 +729,7 @@ main(int argc, char **argv)
> /* Lua interpeter options, e.g. -e and -l */
> int optc = 0;
> const char **optv = NULL;
> - auto guard = make_scoped_guard([=]{ if (optc) free(optv); });
> + auto guard = make_scoped_guard([&optc, &optv]{ if (optc) free(optv); });
>
> static struct option longopts[] = {
> {"help", no_argument, 0, 'h'},
> --
> 2.7.4
>
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