Re: [RFC PATCH] Subject: [RFC PATCH] plugins: Passed the parsed arguments directly to plugins

[Alex Bennée]

Mahmoud Mandour <ma.mandourr@gmail.com> writes:

The subject got a bit mangled. I usually send single one off patches
directly from the command line like this:

  git send-email --subject-prefix "RFC PATCH" HEAD^.. --to qemu HEAD^..

> Arguments were passed to plugins in the following form:
>     -plugin path/to/plugin,arg="positional_arg=value",arg="second_arg"
>
> This patch removes the need for "arg" so that the argument name itself
> is now expected and passed directly to the plugin.
>
> Now options can be passed in the following manner:
>     -plugin path/to/plugin,positional_arg=value,second_arg
>
> Since short boolean arguments are deprecated, passing an argument that
> takes no value will trigger a warning saying that the user should use a
> full "arg_name=on" instead of just "arg_name". In either case, the
> argument is passed to the plugin as only the name, omitting the "=on"
> part.
>
> Signed-off-by: Mahmoud Mandour <ma.mandourr@gmail.com>
> ---
>  plugins/loader.c | 12 ++++++++----
>  1 file changed, 8 insertions(+), 4 deletions(-)
>
> diff --git a/plugins/loader.c b/plugins/loader.c
> index 05df40398d..7f32b8c8bd 100644
> --- a/plugins/loader.c
> +++ b/plugins/loader.c
> @@ -94,6 +94,7 @@ static int plugin_add(void *opaque, const char *name, const 
> char *value,
>  {
>      struct qemu_plugin_parse_arg *arg = opaque;
>      struct qemu_plugin_desc *p;
> +    char *full_arg;
>  
>      if (strcmp(name, "file") == 0) {
>          if (strcmp(value, "") == 0) {
> @@ -107,7 +108,7 @@ static int plugin_add(void *opaque, const char *name, 
> const char *value,
>              QTAILQ_INSERT_TAIL(arg->head, p, entry);
>          }
>          arg->curr = p;
> -    } else if (strcmp(name, "arg") == 0) {
> +    } else {

Unfortunately I think we also want to support the arg= form for now and
also update the deprecated.rst and plugin.rst documentation to point to
the new format.

>          if (arg->curr == NULL) {
>              error_setg(errp, "missing earlier '-plugin file=' option");
>              return 1;
> @@ -115,9 +116,12 @@ static int plugin_add(void *opaque, const char *name, 
> const char *value,
>          p = arg->curr;
>          p->argc++;
>          p->argv = g_realloc_n(p->argv, p->argc, sizeof(char *));
> -        p->argv[p->argc - 1] = g_strdup(value);
> -    } else {
> -        error_setg(errp, "-plugin: unexpected parameter '%s'; ignored", 
> name);
> +        if (strcmp(value, "on")) {
> +            full_arg = g_strdup_printf("%s=%s", name, value);

We should probably prefer g_strcmp0 to strcmp and an explicit value test
(!= 0) because strcmp is weird with truth/falsity. However as we are
handling the syntactic sugar of adding "on" in the command line I wonder
if we can query QemuOpt directly. Maybe something like:

        /* pass true bools as single arg */
        if (qapi_bool_parse(name, value, &is_true, errp) && is_true) {
            full_arg = g_strdup(name);
        } else {
            full_arg = g_strdup_printf("%s=%s", name, value);
        }


> +        } else {
> +            full_arg = g_strdup(name);
> +        }
> +        p->argv[p->argc - 1] = full_arg;
>      }
>      return 0;
>  }


-- 
Alex Bennée