[PATCH 0/2] qapi: Simplify enum generation

[PATCH 0/2] qapi: Simplify enum generation

[Philippe Mathieu-Daudé]

QAPI generating enum count as part of the enum forces handling
impossible switch cases. Modify qapi/types.py to generate the
enum count as a definition.
Do not try to cover the unreachable 'default' case.
Clean files covering unreachable foo__MAX case.

Philippe Mathieu-Daudé (2):
  qapi: Do not generate default switch case in
    gen_visit_object_members()
  qapi: Generate enum count as definition in gen_enum_lookup()

 audio/audio.c          |  6 ------
 audio/audio_template.h |  3 ---
 migration/migration.c  |  2 --
 replay/replay-input.c  | 12 ------------
 scripts/qapi/types.py  | 11 +++++++----
 scripts/qapi/visit.py  |  2 --
 softmmu/tpm-hmp-cmds.c |  2 --
 ui/input-linux.c       |  4 ----
 ui/input.c             |  6 ------
 9 files changed, 7 insertions(+), 41 deletions(-)

-- 
2.38.1

[PATCH 1/2] qapi: Do not generate default switch case in gen_visit_object_members()

[Philippe Mathieu-Daudé]

When iterating over a QAPISchemaEnumType, all possible
values are covered. The 'default' switch case is unreachable,
remove it.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
---
 scripts/qapi/visit.py | 2 --
 1 file changed, 2 deletions(-)

diff --git a/scripts/qapi/visit.py b/scripts/qapi/visit.py
index 26a584ee4c..f66a31a963 100644
--- a/scripts/qapi/visit.py
+++ b/scripts/qapi/visit.py
@@ -159,8 +159,6 @@ def gen_visit_object_members(name: str,
 
             ret += var.ifcond.gen_endif()
         ret += mcgen('''
-    default:
-        abort();
     }
 ''')
 
-- 
2.38.1

Re: [PATCH 1/2] qapi: Do not generate default switch case in gen_visit_object_members()

[Juan Quintela]

Philippe Mathieu-Daudé <philmd@linaro.org> wrote:
> When iterating over a QAPISchemaEnumType, all possible
> values are covered. The 'default' switch case is unreachable,
> remove it.
>
> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>

Reviewed-by: Juan Quintela <quintela@redhat.com>

Althought my qapi is rusty.

Re: [PATCH 1/2] qapi: Do not generate default switch case in gen_visit_object_members()

[Markus Armbruster]

Philippe Mathieu-Daudé <philmd@linaro.org> writes:

> When iterating over a QAPISchemaEnumType, all possible
> values are covered. The 'default' switch case is unreachable,
> remove it.
>
> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> ---
>  scripts/qapi/visit.py | 2 --
>  1 file changed, 2 deletions(-)
>
> diff --git a/scripts/qapi/visit.py b/scripts/qapi/visit.py
> index 26a584ee4c..f66a31a963 100644
> --- a/scripts/qapi/visit.py
> +++ b/scripts/qapi/visit.py
> @@ -159,8 +159,6 @@ def gen_visit_object_members(name: str,
>  
>              ret += var.ifcond.gen_endif()
>          ret += mcgen('''
> -    default:
> -        abort();
>      }
>  ''')

This results in a bunch of warnings like

    warning: enumeration value ‘FOO__MAX’ not handled in switch [-Wswitch]

Obvious fix: squash into the next patch.

[PATCH 2/2] qapi: Generate enum count as definition in gen_enum_lookup()

[Philippe Mathieu-Daudé]

QAPI's gen_enum() generates QAPI enum values and the number
of this values (as foo__MAX).
The number of entries in an enum type is not part of the
enumerated values, but we generate it as such. See for
example:

  typedef enum OnOffAuto {
      ON_OFF_AUTO_AUTO,
      ON_OFF_AUTO_ON,
      ON_OFF_AUTO_OFF,
      ON_OFF_AUTO__MAX,        <---------
  } OnOffAuto;

Instead of declaring the enum count as the last enumerated
value, #define it, so it is not part of the enum. The previous
example becomes:

  typedef enum OnOffAuto {
      ON_OFF_AUTO_AUTO,
      ON_OFF_AUTO_ON,
      ON_OFF_AUTO_OFF,
  #define ON_OFF_AUTO__MAX 3   <---------
  } OnOffAuto;

Since Clang enables the -Wswitch warning by default [*], remove all
pointless foo__MAX cases in switch statement, in order to avoid:

 audio/audio.c:2231:10: error: case value not in enumerated type 'AudioFormat' (aka 'enum AudioFormat') [-Wswitch]
    case AUDIO_FORMAT__MAX:
         ^
 ui/input.c:233:14: error: case value not in enumerated type 'KeyValueKind' (aka 'enum KeyValueKind') [-Wswitch]
        case KEY_VALUE_KIND__MAX:
             ^
 ...

[*] https://clang.llvm.org/docs/DiagnosticsReference.html#wswitch
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
---
 audio/audio.c          |  6 ------
 audio/audio_template.h |  3 ---
 migration/migration.c  |  2 --
 replay/replay-input.c  | 12 ------------
 scripts/qapi/types.py  | 11 +++++++----
 softmmu/tpm-hmp-cmds.c |  2 --
 ui/input-linux.c       |  4 ----
 ui/input.c             |  6 ------
 8 files changed, 7 insertions(+), 39 deletions(-)

diff --git a/audio/audio.c b/audio/audio.c
index 4290309d18..57130c44f6 100644
--- a/audio/audio.c
+++ b/audio/audio.c
@@ -2079,9 +2079,6 @@ void audio_create_pdos(Audiodev *dev)
         CASE(SPICE, spice, );
 #endif
         CASE(WAV, wav, );
-
-    case AUDIODEV_DRIVER__MAX:
-        abort();
     };
 }
 
@@ -2227,9 +2224,6 @@ int audioformat_bytes_per_sample(AudioFormat fmt)
     case AUDIO_FORMAT_S32:
     case AUDIO_FORMAT_F32:
         return 4;
-
-    case AUDIO_FORMAT__MAX:
-        ;
     }
     abort();
 }
diff --git a/audio/audio_template.h b/audio/audio_template.h
index 42b4712acb..58e1255d7a 100644
--- a/audio/audio_template.h
+++ b/audio/audio_template.h
@@ -369,9 +369,6 @@ AudiodevPerDirectionOptions *glue(audio_get_pdo_, TYPE)(Audiodev *dev)
 #endif
     case AUDIODEV_DRIVER_WAV:
         return dev->u.wav.TYPE;
-
-    case AUDIODEV_DRIVER__MAX:
-        break;
     }
     abort();
 }
diff --git a/migration/migration.c b/migration/migration.c
index ae2025d9d8..bdadab3b5e 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -2220,8 +2220,6 @@ bool migration_is_idle(void)
     case MIGRATION_STATUS_DEVICE:
     case MIGRATION_STATUS_WAIT_UNPLUG:
         return false;
-    case MIGRATION_STATUS__MAX:
-        g_assert_not_reached();
     }
 
     return false;
diff --git a/replay/replay-input.c b/replay/replay-input.c
index 1147e3d34e..c6de8e33ac 100644
--- a/replay/replay-input.c
+++ b/replay/replay-input.c
@@ -38,9 +38,6 @@ void replay_save_input_event(InputEvent *evt)
             replay_put_dword(key->key->u.qcode.data);
             replay_put_byte(key->down);
             break;
-        case KEY_VALUE_KIND__MAX:
-            /* keep gcc happy */
-            break;
         }
         break;
     case INPUT_EVENT_KIND_BTN:
@@ -58,9 +55,6 @@ void replay_save_input_event(InputEvent *evt)
         replay_put_dword(move->axis);
         replay_put_qword(move->value);
         break;
-    case INPUT_EVENT_KIND__MAX:
-        /* keep gcc happy */
-        break;
     }
 }
 
@@ -89,9 +83,6 @@ InputEvent *replay_read_input_event(void)
             evt.u.key.data->key->u.qcode.data = (QKeyCode)replay_get_dword();
             evt.u.key.data->down = replay_get_byte();
             break;
-        case KEY_VALUE_KIND__MAX:
-            /* keep gcc happy */
-            break;
         }
         break;
     case INPUT_EVENT_KIND_BTN:
@@ -109,9 +100,6 @@ InputEvent *replay_read_input_event(void)
         evt.u.abs.data->axis = (InputAxis)replay_get_dword();
         evt.u.abs.data->value = replay_get_qword();
         break;
-    case INPUT_EVENT_KIND__MAX:
-        /* keep gcc happy */
-        break;
     }
 
     return QAPI_CLONE(InputEvent, &evt);
diff --git a/scripts/qapi/types.py b/scripts/qapi/types.py
index c39d054d2c..b24bcb40ad 100644
--- a/scripts/qapi/types.py
+++ b/scripts/qapi/types.py
@@ -86,16 +86,13 @@ def gen_enum_lookup(name: str,
 def gen_enum(name: str,
              members: List[QAPISchemaEnumMember],
              prefix: Optional[str] = None) -> str:
-    # append automatically generated _MAX value
-    enum_members = members + [QAPISchemaEnumMember('_MAX', None)]
-
     ret = mcgen('''
 
 typedef enum %(c_name)s {
 ''',
                 c_name=c_name(name))
 
-    for memb in enum_members:
+    for memb in members:
         ret += memb.ifcond.gen_if()
         ret += mcgen('''
     %(c_enum)s,
@@ -103,6 +100,12 @@ def gen_enum(name: str,
                      c_enum=c_enum_const(name, memb.name, prefix))
         ret += memb.ifcond.gen_endif()
 
+    ret += mcgen('''
+#define %(c_name)s %(c_length)s
+''',
+                 c_name=c_enum_const(name, '_MAX', prefix),
+                 c_length=len(members))
+
     ret += mcgen('''
 } %(c_name)s;
 ''',
diff --git a/softmmu/tpm-hmp-cmds.c b/softmmu/tpm-hmp-cmds.c
index 9ed6ad6c4d..5a354cf6ac 100644
--- a/softmmu/tpm-hmp-cmds.c
+++ b/softmmu/tpm-hmp-cmds.c
@@ -52,8 +52,6 @@ void hmp_info_tpm(Monitor *mon, const QDict *qdict)
             teo = ti->options->u.emulator.data;
             monitor_printf(mon, ",chardev=%s", teo->chardev);
             break;
-        case TPM_TYPE__MAX:
-            break;
         }
         monitor_printf(mon, "\n");
         c++;
diff --git a/ui/input-linux.c b/ui/input-linux.c
index e572a2e905..a6e7574422 100644
--- a/ui/input-linux.c
+++ b/ui/input-linux.c
@@ -120,10 +120,6 @@ static bool input_linux_check_toggle(InputLinux *il)
         return (il->keydown[KEY_LEFTCTRL] ||
                 il->keydown[KEY_RIGHTCTRL]) &&
             il->keydown[KEY_SCROLLLOCK];
-
-    case GRAB_TOGGLE_KEYS__MAX:
-        /* avoid gcc error */
-        break;
     }
     return false;
 }
diff --git a/ui/input.c b/ui/input.c
index f2d1e7a3a7..ca8f49a403 100644
--- a/ui/input.c
+++ b/ui/input.c
@@ -230,9 +230,6 @@ static void qemu_input_event_trace(QemuConsole *src, InputEvent *evt)
             name = QKeyCode_str(key->key->u.qcode.data);
             trace_input_event_key_qcode(idx, name, key->down);
             break;
-        case KEY_VALUE_KIND__MAX:
-            /* keep gcc happy */
-            break;
         }
         break;
     case INPUT_EVENT_KIND_BTN:
@@ -250,9 +247,6 @@ static void qemu_input_event_trace(QemuConsole *src, InputEvent *evt)
         name = InputAxis_str(move->axis);
         trace_input_event_abs(idx, name, move->value);
         break;
-    case INPUT_EVENT_KIND__MAX:
-        /* keep gcc happy */
-        break;
     }
 }
 
-- 
2.38.1

Re: [PATCH 2/2] qapi: Generate enum count as definition in gen_enum_lookup()

[Richard Henderson]

On 2/24/23 05:54, Philippe Mathieu-Daudé wrote:
> QAPI's gen_enum() generates QAPI enum values and the number
> of this values (as foo__MAX).
> The number of entries in an enum type is not part of the
> enumerated values, but we generate it as such. See for
> example:
> 
>    typedef enum OnOffAuto {
>        ON_OFF_AUTO_AUTO,
>        ON_OFF_AUTO_ON,
>        ON_OFF_AUTO_OFF,
>        ON_OFF_AUTO__MAX,        <---------
>    } OnOffAuto;
> 
> Instead of declaring the enum count as the last enumerated
> value, #define it, so it is not part of the enum. The previous
> example becomes:
> 
>    typedef enum OnOffAuto {
>        ON_OFF_AUTO_AUTO,
>        ON_OFF_AUTO_ON,
>        ON_OFF_AUTO_OFF,
>    #define ON_OFF_AUTO__MAX 3   <---------
>    } OnOffAuto;
> 
> Since Clang enables the -Wswitch warning by default [*], remove all
> pointless foo__MAX cases in switch statement, in order to avoid:
> 
>   audio/audio.c:2231:10: error: case value not in enumerated type 'AudioFormat' (aka 'enum AudioFormat') [-Wswitch]
>      case AUDIO_FORMAT__MAX:
>           ^
>   ui/input.c:233:14: error: case value not in enumerated type 'KeyValueKind' (aka 'enum KeyValueKind') [-Wswitch]
>          case KEY_VALUE_KIND__MAX:
>               ^
>   ...
> 
> [*]https://clang.llvm.org/docs/DiagnosticsReference.html#wswitch
> Signed-off-by: Philippe Mathieu-Daudé<philmd@linaro.org>
> ---

Yay!

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

r~

Re: [PATCH 2/2] qapi: Generate enum count as definition in gen_enum_lookup()

[Juan Quintela]

Philippe Mathieu-Daudé <philmd@linaro.org> wrote:
> QAPI's gen_enum() generates QAPI enum values and the number
> of this values (as foo__MAX).
> The number of entries in an enum type is not part of the
> enumerated values, but we generate it as such. See for
> example:
>
>   typedef enum OnOffAuto {
>       ON_OFF_AUTO_AUTO,
>       ON_OFF_AUTO_ON,
>       ON_OFF_AUTO_OFF,
>       ON_OFF_AUTO__MAX,        <---------
>   } OnOffAuto;
>
> Instead of declaring the enum count as the last enumerated
> value, #define it, so it is not part of the enum. The previous
> example becomes:
>
>   typedef enum OnOffAuto {
>       ON_OFF_AUTO_AUTO,
>       ON_OFF_AUTO_ON,
>       ON_OFF_AUTO_OFF,
>   #define ON_OFF_AUTO__MAX 3   <---------
>   } OnOffAuto;
>
> Since Clang enables the -Wswitch warning by default [*], remove all
> pointless foo__MAX cases in switch statement, in order to avoid:
>
>  audio/audio.c:2231:10: error: case value not in enumerated type 'AudioFormat' (aka 'enum AudioFormat') [-Wswitch]
>     case AUDIO_FORMAT__MAX:
>          ^
>  ui/input.c:233:14: error: case value not in enumerated type 'KeyValueKind' (aka 'enum KeyValueKind') [-Wswitch]
>         case KEY_VALUE_KIND__MAX:
>              ^
>  ...
>
> [*] https://clang.llvm.org/docs/DiagnosticsReference.html#wswitch
> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>

Reviewed-by: Juan Quintela <quintela@redhat.com>

This other is very nice.

Thanks, Juan.

Re: [PATCH 2/2] qapi: Generate enum count as definition in gen_enum_lookup()

[Markus Armbruster]

Philippe Mathieu-Daudé <philmd@linaro.org> writes:

> QAPI's gen_enum() generates QAPI enum values and the number
> of this values (as foo__MAX).
> The number of entries in an enum type is not part of the
> enumerated values, but we generate it as such. See for
> example:
>
>   typedef enum OnOffAuto {
>       ON_OFF_AUTO_AUTO,
>       ON_OFF_AUTO_ON,
>       ON_OFF_AUTO_OFF,
>       ON_OFF_AUTO__MAX,        <---------
>   } OnOffAuto;
>
> Instead of declaring the enum count as the last enumerated
> value, #define it, so it is not part of the enum. The previous
> example becomes:
>
>   typedef enum OnOffAuto {
>       ON_OFF_AUTO_AUTO,
>       ON_OFF_AUTO_ON,
>       ON_OFF_AUTO_OFF,
>   #define ON_OFF_AUTO__MAX 3   <---------
>   } OnOffAuto;

I'm in favour.  In fact, I've wanted to do this for a while, just never
got around to it.

> Since Clang enables the -Wswitch warning by default [*], remove all
> pointless foo__MAX cases in switch statement, in order to avoid:
>
>  audio/audio.c:2231:10: error: case value not in enumerated type 'AudioFormat' (aka 'enum AudioFormat') [-Wswitch]
>     case AUDIO_FORMAT__MAX:
>          ^
>  ui/input.c:233:14: error: case value not in enumerated type 'KeyValueKind' (aka 'enum KeyValueKind') [-Wswitch]
>         case KEY_VALUE_KIND__MAX:
>              ^
>  ...
>
> [*] https://clang.llvm.org/docs/DiagnosticsReference.html#wswitch
> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>

Falls apart when the enum is empty:

    gcc -m64 -mcx16 -Iqga/qemu-ga.p -Iqga -I../qga -I. -Iqapi -Itrace -Iui -Iui/shader -I/usr/include/glib-2.0 -I/usr/lib64/glib-2.0/include -I/usr/include/sysprof-4 -fdiagnostics-color=auto -Wall -Winvalid-pch -std=gnu11 -O0 -g -isystem /work/armbru/qemu/linux-headers -isystem linux-headers -iquote . -iquote /work/armbru/qemu -iquote /work/armbru/qemu/include -iquote /work/armbru/qemu/tcg/i386 -pthread -D_GNU_SOURCE -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -fno-strict-aliasing -fno-common -fwrapv -Wundef -Wwrite-strings -Wmissing-prototypes -Wstrict-prototypes -Wredundant-decls -Wold-style-declaration -Wold-style-definition -Wtype-limits -Wformat-security -Wformat-y2k -Winit-self -Wignored-qualifiers -Wempty-body -Wnested-externs -Wendif-labels -Wexpansion-to-defined -Wimplicit-fallthrough=2 -Wmissing-format-attribute -Wno-missing-include-dirs -Wno-shift-negative-value -Wno-psabi -fstack-protector-strong -fPIE -MD -MQ qga/qemu-ga.p/meson-generated_.._qga-qapi-emit-events.c.o -MF qga/qemu-ga.p/meson-generated_.._qga-qapi-emit-events.c.o.d -o qga/qemu-ga.p/meson-generated_.._qga-qapi-emit-events.c.o -c qga/qga-qapi-emit-events.c
    In file included from qga/qga-qapi-emit-events.c:14:
    qga/qga-qapi-emit-events.h:20:1: error: empty enum is invalid
       20 | } qga_QAPIEvent;
          | ^

qga/qapi-schema.json does not define any events, so its (implicitly
defined) event enumeration comes out empty.

We could detect this, and either emit a dummy event, or suppress code
generation for events entirely.

Explicitly defined enumerations may also be empty.  qapi-code-gen.rst
says:

    Nothing prevents an empty enumeration, although it is probably not
    useful.

We could forbid empty enumerations.

Speaking of qapi-code-gen.rst: it also needs an update.  Search for
__MAX.

Re: [PATCH 2/2] qapi: Generate enum count as definition in gen_enum_lookup()

[Philippe Mathieu-Daudé]

On 27/2/23 14:10, Markus Armbruster wrote:
> Philippe Mathieu-Daudé <philmd@linaro.org> writes:
> 
>> QAPI's gen_enum() generates QAPI enum values and the number
>> of this values (as foo__MAX).
>> The number of entries in an enum type is not part of the
>> enumerated values, but we generate it as such. See for
>> example:
>>
>>    typedef enum OnOffAuto {
>>        ON_OFF_AUTO_AUTO,
>>        ON_OFF_AUTO_ON,
>>        ON_OFF_AUTO_OFF,
>>        ON_OFF_AUTO__MAX,        <---------
>>    } OnOffAuto;
>>
>> Instead of declaring the enum count as the last enumerated
>> value, #define it, so it is not part of the enum. The previous
>> example becomes:
>>
>>    typedef enum OnOffAuto {
>>        ON_OFF_AUTO_AUTO,
>>        ON_OFF_AUTO_ON,
>>        ON_OFF_AUTO_OFF,
>>    #define ON_OFF_AUTO__MAX 3   <---------
>>    } OnOffAuto;
> 
> I'm in favour.  In fact, I've wanted to do this for a while, just never
> got around to it.
> 
>> Since Clang enables the -Wswitch warning by default [*], remove all
>> pointless foo__MAX cases in switch statement, in order to avoid:
>>
>>   audio/audio.c:2231:10: error: case value not in enumerated type 'AudioFormat' (aka 'enum AudioFormat') [-Wswitch]
>>      case AUDIO_FORMAT__MAX:
>>           ^
>>   ui/input.c:233:14: error: case value not in enumerated type 'KeyValueKind' (aka 'enum KeyValueKind') [-Wswitch]
>>          case KEY_VALUE_KIND__MAX:
>>               ^
>>   ...
>>
>> [*] https://clang.llvm.org/docs/DiagnosticsReference.html#wswitch
>> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> 
> Falls apart when the enum is empty:
> 
>      gcc -m64 -mcx16 -Iqga/qemu-ga.p -Iqga -I../qga -I. -Iqapi -Itrace -Iui -Iui/shader -I/usr/include/glib-2.0 -I/usr/lib64/glib-2.0/include -I/usr/include/sysprof-4 -fdiagnostics-color=auto -Wall -Winvalid-pch -std=gnu11 -O0 -g -isystem /work/armbru/qemu/linux-headers -isystem linux-headers -iquote . -iquote /work/armbru/qemu -iquote /work/armbru/qemu/include -iquote /work/armbru/qemu/tcg/i386 -pthread -D_GNU_SOURCE -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -fno-strict-aliasing -fno-common -fwrapv -Wundef -Wwrite-strings -Wmissing-prototypes -Wstrict-prototypes -Wredundant-decls -Wold-style-declaration -Wold-style-definition -Wtype-limits -Wformat-security -Wformat-y2k -Winit-self -Wignored-qualifiers -Wempty-body -Wnested-externs -Wendif-labels -Wexpansion-to-defined -Wimplicit-fallthrough=2 -Wmissing-format-attribute -Wno-missing-include-dirs -Wno-shift-negative-value -Wno-psabi -fstack-protector-strong -fPIE -MD -MQ qga/qemu-ga.p/meson-generated_.._qga-qapi-emit-events.c.o -MF qga/qemu-ga.p/meson-generated_.._qga-qapi-emit-events.c.o.d -o qga/qemu-ga.p/meson-generated_.._qga-qapi-emit-events.c.o -c qga/qga-qapi-emit-events.c
>      In file included from qga/qga-qapi-emit-events.c:14:
>      qga/qga-qapi-emit-events.h:20:1: error: empty enum is invalid
>         20 | } qga_QAPIEvent;
>            | ^

While I could find that in the C++ standard, I couldn't in the C one.

I wonder if in that case QAPI should generate foo__MAX = 0. No code /
structure should use an enum type which doesn't contain any member...