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

[Wenchao Xia <xiawenc@linux.vnet.ibm.com>]

于 2013-7-18 3:39, Luiz Capitulino 写道:
> 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.
>
   I'll use assert().

>> +    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
   will fail the function if nb_args > MAX_ARGS in next version.

> 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)
>


-- 
Best Regards

Wenchao Xia