Re: [Qemu-devel] [PATCH v2 3/3] tests: Enhance qobject output to cover partial visit

[Markus Armbruster]

Eric Blake <address@hidden> writes:

> Add a test that proves (at least when run under valgrind) that
> we are correctly handling allocated memory even when a visit
> is aborted in the middle for whatever other reason.
>
> See commit f24582d "qapi: fix double free in
> qmp_output_visitor_cleanup()" for a fix that was lacking
> testsuite exposure prior to this patch.
>
> Signed-off-by: Eric Blake <address@hidden>
>
> ---
> v2: rebase (and hence retitle), add list & alternate coverage
> ---
>  tests/test-qobject-output-visitor.c | 39 
> +++++++++++++++++++++++++++++++++++++
>  1 file changed, 39 insertions(+)
>
> diff --git a/tests/test-qobject-output-visitor.c 
> b/tests/test-qobject-output-visitor.c
> index c2e0f43..fdae0d5 100644
> --- a/tests/test-qobject-output-visitor.c
> +++ b/tests/test-qobject-output-visitor.c
> @@ -254,6 +254,43 @@ static void 
> test_visitor_out_struct_errors(TestOutputVisitorData *data,
>  }
>
>
> +static void test_visitor_out_partial_visit(TestOutputVisitorData *data,
> +                                           const void *unused)
> +{
> +    /* Various checks that a mid-visit abort doesn't leak or double-free. */
> +    const char *str = "hi";
> +    Error *err = NULL;
> +    UserDefAlternate uda = { .type = QTYPE_QDICT,
> +                             .u.udfu = { .integer = 1,
> +                                         .string = (char *) "bye",
> +                                         .enum1 = -1 } };
> +    UserDefAlternate *obj = &uda;
> +
> +    /* Abort within a nested object with no data members */
> +    visit_start_struct(data->ov, NULL, NULL, 0, &error_abort);
> +    visit_start_struct(data->ov, "nested", NULL, 0, &error_abort);
> +    visitor_reset(data);
> +
> +    /* Abort in the middle of a list of strings */
> +    visit_start_list(data->ov, "list", NULL, 0, &error_abort);
> +    visit_type_str(data->ov, NULL, (char **)&str, &error_abort);
> +    visit_type_str(data->ov, NULL, (char **)&str, &error_abort);
> +    visitor_reset(data);
> +
> +    /* Abort in the middle of an alternate. Alternates can't be
> +     * virtually visited, so we get to inline the first half of
> +     * visit_type_UserDefAlternate(). */
> +    visit_start_alternate(data->ov, NULL, (GenericAlternate **)&obj,
> +                          sizeof(uda), false, &error_abort);
> +    visit_start_struct(data->ov, NULL, NULL, 0, &error_abort);
> +    visit_type_UserDefUnionBase_members(data->ov,
> +                                        (UserDefUnionBase *)&uda.u.udfu,
> +                                        &err);
> +    error_free_or_abort(&err);

Why does this fail?

> +    visitor_reset(data);
> +}
> +
> +
>  static void test_visitor_out_list(TestOutputVisitorData *data,
>                                    const void *unused)
>  {
> @@ -817,6 +854,8 @@ int main(int argc, char **argv)
>                              &out_visitor_data, 
> test_visitor_out_struct_nested);
>      output_visitor_test_add("/visitor/output/struct-errors",
>                              &out_visitor_data, 
> test_visitor_out_struct_errors);
> +    output_visitor_test_add("/visitor/output/partial-visit",
> +                            &out_visitor_data, 
> test_visitor_out_partial_visit);
>      output_visitor_test_add("/visitor/output/list",
>                              &out_visitor_data, test_visitor_out_list);
>      output_visitor_test_add("/visitor/output/any",