Re: [Qemu-devel] [PATCH V6 08/13] monitor: refine parse_cmdline()

[Luiz Capitulino <lcapitulino@redhat.com>]

On Thu, 11 Jul 2013 11:13:44 +0800
Wenchao Xia <xiawenc@linux.vnet.ibm.com> wrote:

> Since this function will be used by help_cmd() later, so improve
> it to make it more generic and easier to use. free_cmdline_args()
> is added to as paired function to free the result.
> 
> Signed-off-by: Wenchao Xia <xiawenc@linux.vnet.ibm.com>
> ---
>  monitor.c |   52 ++++++++++++++++++++++++++++++++++++++--------------
>  1 files changed, 38 insertions(+), 14 deletions(-)
> 
> diff --git a/monitor.c b/monitor.c
> index db63223..2d4f699 100644
> --- a/monitor.c
> +++ b/monitor.c
> @@ -801,9 +801,31 @@ static int get_str(char *buf, int buf_size, const char **pp)
>  
>  #define MAX_ARGS 16
>  
> -/* NOTE: this parser is an approximate form of the real command parser */
> -static void parse_cmdline(const char *cmdline,
> -                          int *pnb_args, char **args)
> +static void free_cmdline_args(char **args, int nb_args)
> +{
> +    int i;
> +
> +    nb_args = nb_args < MAX_ARGS ? nb_args : MAX_ARGS;

Why is this needed? nb_args is guaranteed to be at most MAX_ARGS,
isn't it? If you really want to ensure it, then you can assert() it.

> +    for (i = 0; i < nb_args; i++) {
> +        g_free(args[i]);
> +    }
> +
> +}
> +
> +/*
> + * Parse the command line to get valid args.
> + * @cmdline: command line to be parsed.
> + * @pnb_args: location to store the number of args, must NOT be NULL.
> + * @args: location to store the args, which should be freed by caller, must
> + *        NOT be NULL.
> + *
> + * Returns 0 on success, negative on failure.
> + *
> + * NOTE: this parser is an approximate form of the real command parser. Number
> + *       of args have a limit of MAX_ARGS.
> + */
> +static int parse_cmdline(const char *cmdline,
> +                         int *pnb_args, char **args)
>  {
>      const char *p;
>      int nb_args, ret;
> @@ -811,24 +833,26 @@ static void parse_cmdline(const char *cmdline,
>  
>      p = cmdline;
>      nb_args = 0;
> -    for (;;) {
> +    while (nb_args < MAX_ARGS) {

I think it would be better to fail if nb_args > MAX_ARGS. Well, ideally
we shouldn't have any artificial limit, but I'd guess that dropping
MAX_ARGS goes a bit to far for this series' scope.

>          while (qemu_isspace(*p)) {
>              p++;
>          }
>          if (*p == '\0') {
>              break;
>          }
> -        if (nb_args >= MAX_ARGS) {
> -            break;
> -        }
>          ret = get_str(buf, sizeof(buf), &p);
> -        args[nb_args] = g_strdup(buf);
> -        nb_args++;
>          if (ret < 0) {
> -            break;
> +            goto fail;
>          }
> +        args[nb_args] = g_strdup(buf);
> +        nb_args++;
>      }
>      *pnb_args = nb_args;
> +    return 0;
> +
> + fail:
> +    free_cmdline_args(args, nb_args);
> +    return -1;
>  }
>  
>  static void help_cmd_dump(Monitor *mon, const mon_cmd_t *cmds,
> @@ -4144,7 +4168,9 @@ static void monitor_find_completion(Monitor *mon,
>      const mon_cmd_t *cmd;
>      MonitorBlockComplete mbs;
>  
> -    parse_cmdline(cmdline, &nb_args, args);
> +    if (parse_cmdline(cmdline, &nb_args, args) < 0) {
> +        return;
> +    }
>  #ifdef DEBUG_COMPLETION
>      for (i = 0; i < nb_args; i++) {
>          monitor_printf(mon, "arg%d = '%s'\n", i, args[i]);
> @@ -4234,9 +4260,7 @@ static void monitor_find_completion(Monitor *mon,
>      }
>  
>  cleanup:
> -    for (i = 0; i < nb_args; i++) {
> -        g_free(args[i]);
> -    }
> +    free_cmdline_args(args, nb_args);
>  }
>  
>  static int monitor_can_read(void *opaque)