Re: [PATCH v2 03/12] virsh: Conditionally Ignore the first entry in list of completions

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On 05/10/2018 05:17 PM, Michal Privoznik wrote:
On 05/08/2018 04:20 PM, Lin Ma wrote:
The first entry in the returned array is the substitution for TEXT. It
causes unnecessary output if other commands or options share the same
prefix, e.g.

$ virsh des<TAB><TAB>
des      desc     destroy

or

$ virsh domblklist --d<TAB><TAB>
--d        --details  --domain

This patch fixes the above issue.

Signed-off-by: Lin Ma <lma@xxxxxxxx>
---
  tools/vsh.c | 6 +++++-
  1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/tools/vsh.c b/tools/vsh.c
index 73ec007e56..57f7589b53 100644
--- a/tools/vsh.c
+++ b/tools/vsh.c
@@ -3458,6 +3458,7 @@ cmdComplete(vshControl *ctl, const vshCmd *cmd)
      const vshCmdOpt *opt = NULL;
      char **matches = NULL, **iter;
      virBuffer buf = VIR_BUFFER_INITIALIZER;
+    int n;
This needs to be size_t. Even though it's not used to directly access
entries of @matches array, it kind of is. It's used to count them. And
int is not guaranteed to be able to address all of them.

if (vshCommandOptStringQuiet(ctl, cmd, "string", &arg) <= 0)
          goto cleanup;
@@ -3493,8 +3494,11 @@ cmdComplete(vshControl *ctl, const vshCmd *cmd)
      if (!(matches = vshReadlineCompletion(arg, 0, 0)))
          goto cleanup;
- for (iter = matches; *iter; iter++)
+    for (n = 0, iter = matches; *iter; iter++, n++) {
+        if (n == 0 && matches[1])
+            continue;
This can be rewritten so that we don't need @n at all:

   if (iter == matches && matches[1])
       continue;

Or even better, just start iterating not from the first but second entry:

     for (iter = &matches[1]; *iter; iter++)
         printf("%s\n", *iter);
It seems it can't handle the case that no command or option share the same prefix. say 'event' command, when users type virsh ev<TAB><TAB>, there is no other command sharing 'ev' prefix, in this case, the matches[1] is NULL and we need to print the
value in matches[0],I think we can't skip the first entry in this case.
So the code block 'if (iter == matches && matches[1])  continue;' looks like a better
choice.If you think so,
I'd like to write a patch to do it, Do you agree?
meanwhile, I want to remove those comment due to we can't skip first entry, Do you agree?

This is safe because:
a) @matches is guaranteed to be non-NULL at this point (due to check above),
b) @matches is NULL terminated array and as you and documentation [1]
say, the first entry is substitution for text (which we want to skip).

So even if the array is nothing but the substitution and NULL,
matches[1] will be NULL:

   matches = { "subs", NULL };

Also, I'm adding a small comment because it is not obvious why we are
skipping the first entry.

ACK then.

Michal

1: http://www.delorie.com/gnu/docs/readline/rlman_46.html

Thanks,
Lin

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