Re: [PATCH 7/9] qapi: Generalize enum member policy checking

[Markus Armbruster]

John Snow <jsnow@redhat.com> writes:

> On Mon, Oct 25, 2021 at 1:26 AM Markus Armbruster <armbru@redhat.com> wrote:
>
>> The code to check enumeration value policy can see special feature
>> flag 'deprecated' in QEnumLookup member flags[value].  I want to make
>> feature flag 'unstable' visible there as well, so I can add policy for
>> it.
>>
>> Instead of extending flags[], replace it by @special_features (a
>> bitset of QapiSpecialFeature), because that's how special features get
>> passed around elsewhere.
>>
>> Signed-off-by: Markus Armbruster <armbru@redhat.com>
>> ---
>>  include/qapi/util.h    |  5 +----
>>  qapi/qapi-visit-core.c |  3 ++-
>>  scripts/qapi/types.py  | 22 ++++++++++++----------
>>  3 files changed, 15 insertions(+), 15 deletions(-)
>>
>> diff --git a/include/qapi/util.h b/include/qapi/util.h
>> index 7a8d5c7d72..0cc98db9f9 100644
>> --- a/include/qapi/util.h
>> +++ b/include/qapi/util.h
>> @@ -15,12 +15,9 @@ typedef enum {
>>      QAPI_DEPRECATED,
>>  } QapiSpecialFeature;
>>
>> -/* QEnumLookup flags */
>> -#define QAPI_ENUM_DEPRECATED 1
>> -
>>  typedef struct QEnumLookup {
>>      const char *const *array;
>> -    const unsigned char *const flags;
>> +    const unsigned char *const special_features;
>>      const int size;
>>  } QEnumLookup;
>>
>> diff --git a/qapi/qapi-visit-core.c b/qapi/qapi-visit-core.c
>> index b4a81f1757..5572d90efb 100644
>> --- a/qapi/qapi-visit-core.c
>> +++ b/qapi/qapi-visit-core.c
>> @@ -407,7 +407,8 @@ static bool input_type_enum(Visitor *v, const char
>> *name, int *obj,
>>          return false;
>>      }
>>
>> -    if (lookup->flags && (lookup->flags[value] & QAPI_ENUM_DEPRECATED)) {
>> +    if (lookup->special_features
>> +        && (lookup->special_features[value] & QAPI_DEPRECATED)) {
>>          switch (v->compat_policy.deprecated_input) {
>>          case COMPAT_POLICY_INPUT_ACCEPT:
>>              break;
>> diff --git a/scripts/qapi/types.py b/scripts/qapi/types.py
>> index ab2441adc9..3013329c24 100644
>> --- a/scripts/qapi/types.py
>> +++ b/scripts/qapi/types.py
>> @@ -16,7 +16,7 @@
>>  from typing import List, Optional
>>
>>  from .common import c_enum_const, c_name, mcgen
>> -from .gen import QAPISchemaModularCVisitor, ifcontext
>> +from .gen import QAPISchemaModularCVisitor, gen_special_features,
>> ifcontext
>>  from .schema import (
>>      QAPISchema,
>>      QAPISchemaEnumMember,
>> @@ -39,7 +39,7 @@ def gen_enum_lookup(name: str,
>>                      members: List[QAPISchemaEnumMember],
>>                      prefix: Optional[str] = None) -> str:
>>      max_index = c_enum_const(name, '_MAX', prefix)
>> -    flags = ''
>> +    feats = ''
>>      ret = mcgen('''
>>
>>  const QEnumLookup %(c_name)s_lookup = {
>> @@ -54,19 +54,21 @@ def gen_enum_lookup(name: str,
>>  ''',
>>                       index=index, name=memb.name)
>>          ret += memb.ifcond.gen_endif()
>> -        if 'deprecated' in (f.name for f in memb.features):
>> -            flags += mcgen('''
>> -        [%(index)s] = QAPI_ENUM_DEPRECATED,
>> -''',
>> -                           index=index)
>>
>> -    if flags:
>> +        special_features = gen_special_features(memb.features)
>> +        if special_features != '0':
>>
>
> Though, I have to admit the common reoccurrence of this pattern suggests to
> me that gen_special_features really ought to be returning something false-y
> in these cases. Something about testing for the empty case with something
> that represents, but isn't empty, gives me a brief pause.
>
> Not willing to wage war over it.

I habitually start stupid, and when stupid confuses or annoys me later,
I smarten it up some.

Let's see how this instance of "stupid" ages, okay?

>> +            feats += mcgen('''
>> +        [%(index)s] = %(special_features)s,
>> +''',
>> +                           index=index, special_features=special_features)
>> +
>> +    if feats:
>>          ret += mcgen('''
>>      },
>> -    .flags = (const unsigned char[%(max_index)s]) {
>> +    .special_features = (const unsigned char[%(max_index)s]) {
>>  ''',
>>                       max_index=max_index)
>> -        ret += flags
>> +        ret += feats
>>
>>      ret += mcgen('''
>>      },
>> --
>> 2.31.1
>>
>>
> Python bits: Acked-by: John Snow <jsnow@redhat.com>

Thanks!