Eric Blake <ebl...@redhat.com> writes:
> Several spots in the code malloc a string, then wrap it in a
> QString, which has to duplicate the input. Adding a new
> constructor with transfer semantics makes this pattern more
> efficient, comparable to the just-added transfer semantics to
> go from QString back to raw string. Use the new
> qstring_wrap_str() where it makes sense.
>
> The new test still passes under valgrind.
>
> Signed-off-by: Eric Blake <ebl...@redhat.com>
>
> ---
> v4: new patch
> ---
> include/qapi/qmp/qstring.h | 1 +
> block.c | 3 ++-
> block/archipelago.c | 6 ++----
> blockdev.c | 3 +--
> qobject/qstring.c | 25 +++++++++++++++++++++++++
> tests/check-qstring.c | 24 ++++++++++++++++++++++++
> 6 files changed, 55 insertions(+), 7 deletions(-)
>
> diff --git a/include/qapi/qmp/qstring.h b/include/qapi/qmp/qstring.h
> index 2d55c87..97cf776 100644
> --- a/include/qapi/qmp/qstring.h
> +++ b/include/qapi/qmp/qstring.h
> @@ -25,6 +25,7 @@ typedef struct QString {
> QString *qstring_new(void);
> QString *qstring_from_str(const char *str);
> QString *qstring_from_substr(const char *str, int start, int end);
> +QString *qstring_wrap_str(char *str);
> size_t qstring_get_length(const QString *qstring);
> const char *qstring_get_str(const QString *qstring);
> char *qstring_consume_str(QString *qstring);
> diff --git a/block.c b/block.c
> index 551832f..32d06b5 100644
> --- a/block.c
> +++ b/block.c
> @@ -1448,7 +1448,8 @@ static int bdrv_append_temp_snapshot(BlockDriverState
> *bs, int flags,
> qdict_put(snapshot_options, "file.driver",
> qstring_from_str("file"));
> qdict_put(snapshot_options, "file.filename",
> - qstring_from_str(tmp_filename));
> + qstring_wrap_str(tmp_filename));
> + tmp_filename = NULL;
> qdict_put(snapshot_options, "driver",
> qstring_from_str("qcow2"));
>
The g_free(tmp_filename) stays, because there are error paths bypassing
this spot. Good.
> diff --git a/block/archipelago.c b/block/archipelago.c
> index 104f2f9..bfdc14c 100644
> --- a/block/archipelago.c
> +++ b/block/archipelago.c
> @@ -426,13 +426,11 @@ static void archipelago_parse_filename(const char
> *filename, QDict *options,
> parse_filename_opts(filename, errp, &volume, &segment_name, &mport,
> &vport);
>
> if (volume) {
> - qdict_put(options, ARCHIPELAGO_OPT_VOLUME, qstring_from_str(volume));
> - g_free(volume);
> + qdict_put(options, ARCHIPELAGO_OPT_VOLUME, qstring_wrap_str(volume));
> }
> if (segment_name) {
> qdict_put(options, ARCHIPELAGO_OPT_SEGMENT,
> - qstring_from_str(segment_name));
> - g_free(segment_name);
> + qstring_wrap_str(segment_name));
> }
> if (mport != NoPort) {
> qdict_put(options, ARCHIPELAGO_OPT_MPORT, qint_from_int(mport));
> diff --git a/blockdev.c b/blockdev.c
> index adc5058..f293cb3 100644
> --- a/blockdev.c
> +++ b/blockdev.c
> @@ -1089,8 +1089,7 @@ DriveInfo *drive_new(QemuOpts *all_opts,
> BlockInterfaceType block_default_type)
> new_id = g_strdup_printf("%s%s%i", if_name[type],
> mediastr, unit_id);
> }
> - qdict_put(bs_opts, "id", qstring_from_str(new_id));
> - g_free(new_id);
> + qdict_put(bs_opts, "id", qstring_wrap_str(new_id));
> }
>
> /* Add virtio block device */
> diff --git a/qobject/qstring.c b/qobject/qstring.c
> index 7a438e9..2af1914 100644
> --- a/qobject/qstring.c
> +++ b/qobject/qstring.c
> @@ -66,6 +66,31 @@ QString *qstring_from_str(const char *str)
> return qstring_from_substr(str, 0, strlen(str) - 1);
> }
>
> +/**
> + * qstring_wrap_str(): Create a new QString around a malloc'd C string
> + *
> + * Returns a strong reference, and caller must not use @str any more.
> + * @str may be NULL, in which case the QString will be "".
I'm not fond of conflating null pointers and "" (see also the trouble
with visit_type_str()). For what it's worth, qstring_from_str(NULL)
crashes. Can we reject null?
> + */
> +QString *qstring_wrap_str(char *str)
> +{
> + QString *qstring;
> +
> + qstring = g_malloc(sizeof(*qstring));
> + qobject_init(QOBJECT(qstring), QTYPE_QSTRING);
> +
> + if (str) {
> + qstring->string = str;
> + qstring->length = strlen(str);
> + } else {
> + qstring->string = g_strdup("");
> + qstring->length = 0;
> + }
> + qstring->capacity = qstring->length;
> +
> + return qstring;
> +}
> +
> static void capacity_increase(QString *qstring, size_t len)
> {
> if (qstring->capacity < (qstring->length + len)) {
> diff --git a/tests/check-qstring.c b/tests/check-qstring.c
> index e6f58e0..0e2e9bd 100644
> --- a/tests/check-qstring.c
> +++ b/tests/check-qstring.c
> @@ -35,6 +35,29 @@ static void qstring_from_str_test(void)
> QDECREF(qstring);
> }
>
> +static void qstring_wrap_str_test(void)
> +{
> + QString *qstring;
> + char *str = g_strdup("QEMU");
> +
> + qstring = qstring_wrap_str(str);
> + g_assert(qstring != NULL);
> + g_assert(qstring->base.refcnt == 1);
> + g_assert(strcmp("QEMU", qstring->string) == 0);
> + g_assert(qobject_type(QOBJECT(qstring)) == QTYPE_QSTRING);
> +
> + QDECREF(qstring);
> +
> + str = NULL;
> + qstring = qstring_wrap_str(str);
> + g_assert(qstring != NULL);
> + g_assert(qstring->base.refcnt == 1);
> + g_assert(strcmp("", qstring->string) == 0);
> + g_assert(qobject_type(QOBJECT(qstring)) == QTYPE_QSTRING);
> +
> + QDECREF(qstring);
> +}
> +
> static void qstring_destroy_test(void)
> {
> QString *qstring = qstring_from_str("destroy test");
> @@ -120,6 +143,7 @@ int main(int argc, char **argv)
> g_test_init(&argc, &argv, NULL);
>
> g_test_add_func("/public/from_str", qstring_from_str_test);
> + g_test_add_func("/public/wrap_str", qstring_wrap_str_test);
> g_test_add_func("/public/destroy", qstring_destroy_test);
> g_test_add_func("/public/get_str", qstring_get_str_test);
> g_test_add_func("/public/append_chr", qstring_append_chr_test);
