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

[Wenchao Xia]

于 2013-7-18 3:39, Luiz Capitulino 写道:

On Thu, 11 Jul 2013 11:13:44 +0800
Wenchao Xia <xiaw...@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 <xiaw...@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