[libvirt PATCH] Do not disable incompatible-pointer-types-discards-qualifiers

[Martin Kletzander]

On Mon, Nov 16, 2020 at 09:21:23AM +0100, Pavel Hrdina wrote:
>On Sun, Nov 15, 2020 at 09:42:40PM +0100, Martin Kletzander wrote:
>> This reverts commit b3710e9a2af402a2b620de570b062294e11190eb.
>>
>> That check is very valuable for our code, but it causes issue with glib >=
>> 2.67.0 when building with clang.
>>
>> The reason is a combination of two commits in glib, firstly fdda405b6b1b which
>> adds a g_atomic_pointer_{set,get} variants that enforce stricter type
>> checking (by removing an extra cast) for compilers that support __typeof__, and
>> commit dce24dc4492d which effectively enabled the new variant of glib's atomic
>> code for clang.  This will not be necessary when glib's issue #600 [0] (8 years
>> old) is fixed.  Thankfully, MR #1719 [1], which is supposed to deal with this
>> issue was opened 3 weeks ago, so there is a slight sliver of hope.
>>
>> [0] https://gitlab.gnome.org/GNOME/glib/-/issues/600
>> [1] https://gitlab.gnome.org/GNOME/glib/-/merge_requests/1719
>>
>> Signed-off-by: Martin Kletzander <mkletzan at redhat.com>
>> ---
>>  meson.build               | 3 ---
>>  src/qemu/qemu_domain.c    | 7 +++++++
>>  src/util/vireventthread.c | 6 ++++++
>>  src/util/viridentity.c    | 6 ++++++
>>  src/util/virobject.c      | 6 ++++++
>>  5 files changed, 25 insertions(+), 3 deletions(-)
>>
>> diff --git a/meson.build b/meson.build
>> index cecaad199d4c..04646e3a078c 100644
>> --- a/meson.build
>> +++ b/meson.build
>> @@ -405,9 +405,6 @@ cc_flags += [
>>    # so use this Clang-specific arg to keep it quiet
>>    '-Wno-typedef-redefinition',
>>
>> -  # Clang complains about casts in G_DEFINE_TYPE(...)
>> -  '-Wno-incompatible-pointer-types-discards-qualifiers',
>> -
>>    # We don't use -Wc++-compat so we have to enable it explicitly
>>    '-Wjump-misses-init',
>>
>> diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
>> index 2158080a56ad..3349476cceae 100644
>> --- a/src/qemu/qemu_domain.c
>> +++ b/src/qemu/qemu_domain.c
>> @@ -330,7 +330,14 @@ struct _qemuDomainLogContext {
>>      virLogManagerPtr manager;
>>  };
>>
>> +#pragma clang diagnostic push
>> +/* Workaround for glib's issue #600 on clang */
>> +#pragma clang diagnostic ignored "-Wincompatible-pointer-types-discards-qualifiers"
>> +
>
>Instead of repeating these two macros you can create our own in
>src/internal.h like we do for other ignores.
>

Oh, I did not know about using _Pragma in macros. I initialy wanted to make a
wrapper macro for the G_DEFINE_TYPE itself, something like:

#define G_DEFINE_TYPE_WITH_WORKAROUND(a, b, c) \
     _Pragma ("clang diagnostic push") \
     _Pragma ("clang diagnostic ignored \"-Wincompatible-pointer-types-discards-qualifiers\"") \
     G_DEFINE_TYPE(a, b, c) \
     _Pragma ("clang diagnostic pop")

But I'm not sure this is something that would not go against other people's
ideas.

>Otherwise looks good.
>
>Pavel


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