Re: [Qemu-devel] [PATCH v7 00/11] Add basic "detach" support for dump-guest-memory

[Peter Xu]

On Thu, Feb 18, 2016 at 08:26:44AM +0100, Markus Armbruster wrote:
> Peter Xu <address@hidden> writes:
> 
> > Changes from v7:
> > - patch 8: use s->dump_info.page_size not TARGET_PAGE_SIZE
> > - patch 10: change DUMP_STATUS_MAX to DUMP_STATUS__MAX (this is to
> >   fix compile error for rebasing to latest master branch, still do
> >   not know why we need this change from generating "_MAX" to
> >   "__MAX" for enum types...)
> 
> Don't ask yourself why something was done, ask git :)

Sorry for my laziness... But it seems that it luckily brings me
another "-S" git trick. Lots of things to learn. :-)

> 
>     $ git-log -S__MAX
>     [...]
>     commit 7fb1cf1606c78c9d5b538f29176fd5a101726a9d
>     Author: Eric Blake <address@hidden>
>     Date:   Wed Nov 18 01:52:57 2015 -0700
> 
> --->    qapi: Don't let implicit enum MAX member collide
> 
>         Now that we guarantee the user doesn't have any enum values
>         beginning with a single underscore, we can use that for our
>         own purposes.  Renaming ENUM_MAX to ENUM__MAX makes it obvious
>         that the sentinel is generated.
> 
>         This patch was mostly generated by applying a temporary patch:
> 
>         |diff --git a/scripts/qapi.py b/scripts/qapi.py
>         |index e6d014b..b862ec9 100644
>         |--- a/scripts/qapi.py
>         |+++ b/scripts/qapi.py
>         |@@ -1570,6 +1570,7 @@ const char *const %(c_name)s_lookup[] = {
>         |     max_index = c_enum_const(name, 'MAX', prefix)
>         |     ret += mcgen('''
>         |     [%(max_index)s] = NULL,
>         |+// %(max_index)s
>         | };
>         | ''',
>         |                max_index=max_index)
> 
>         then running:
> 
>         $ cat qapi-{types,event}.c tests/test-qapi-types.c |
>             sed -n 's,^// \(.*\)MAX,s|\1MAX|\1_MAX|g,p' > list
>         $ git grep -l _MAX | xargs sed -i -f list
> 
>         The only things not generated are the changes in scripts/qapi.py.
> 
>         Rejecting enum members named 'MAX' is now useless, and will be dropped
>         in the next patch.
> 
>         Signed-off-by: Eric Blake <address@hidden>
>         Message-Id: <address@hidden>
>         Reviewed-by: Juan Quintela <address@hidden>
>         [Rebased to current master, commit message tweaked]
>         Signed-off-by: Markus Armbruster <address@hidden>
> 
> I guess this isn't perfectly clear without more context, so let me add
> some.
> 
> The implicit FOO_MAX could collide with the user's FOO_MAX for QAPI
> enumeration values 'max', or case variations thereof.  Commit cf39359
> added extra code to catch that.
> 
> Renaming the implict FOO_MAX to FOO__MAX removes the need for the
> special rule "you can't use 'max' as an enumeration value", because the
> general rule "names starting with '_' are reserved" suffices then.
> 
> Fewer rules is better.

Yah. The commit is reasonable and explanation is clear. Thanks!

Peter

> 
> [...]