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a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1770072077; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=/NDK5VnnkFXqjnSY/+1rjEdw0JQMtPwLYXBs1hRb32U=; b=PZucfKRIrYDLPHjWZY9gS21dogOOo36TZ9deA6bbfJJ4LhvSJ4bePU8qKaW4TCjf8zvZhn QqKBYW7da6Cfa8koQQ25bdNgEvapAVEU7DmRpC99ytgZk3rhJbSp1zSuB9tCKFbxV937OR moqlobYOG3FPDMRCajedy74+Xoz10gs= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1770072077; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=/NDK5VnnkFXqjnSY/+1rjEdw0JQMtPwLYXBs1hRb32U=; b=F3zpVaFVR9O9Y70s2EPRVbHk+T9nb2+Mfaq7gsif/K0tyJPY60cJ0iirq0+y9B3571LESY 4IJDHprtD/RGsuBw== From: Fabiano Rosas To: qemu-devel@nongnu.org Cc: peterx@redhat.com, armbru@redhat.com, ppandit@redhat.com, Michael Roth Subject: [PATCH v2 5/9] qapi: Add QAPI_MERGE Date: Mon, 2 Feb 2026 19:40:57 -0300 Message-ID: <20260202224101.20568-6-farosas@suse.de> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20260202224101.20568-1-farosas@suse.de> References: <20260202224101.20568-1-farosas@suse.de> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Spamd-Result: default: False [-3.01 / 50.00]; BAYES_HAM(-3.00)[99.99%]; MID_CONTAINS_FROM(1.00)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; R_MISSING_CHARSET(0.50)[]; R_DKIM_ALLOW(-0.20)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; MX_GOOD(-0.01)[]; RCVD_COUNT_TWO(0.00)[2]; ARC_NA(0.00)[]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; MIME_TRACE(0.00)[0:+]; RCVD_VIA_SMTP_AUTH(0.00)[]; FUZZY_RATELIMITED(0.00)[rspamd.com]; FROM_EQ_ENVFROM(0.00)[]; RCVD_TLS_ALL(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; RCPT_COUNT_FIVE(0.00)[5]; DKIM_TRACE(0.00)[suse.de:+] X-Spam-Score: -3.01 X-Rspamd-Queue-Id: 5AACE5BCC6 X-Rspamd-Action: no action X-Rspamd-Server: rspamd2.dmz-prg2.suse.org Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=2a07:de40:b251:101:10:150:64:2; envelope-from=farosas@suse.de; helo=smtp-out2.suse.de X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @suse.de) X-ZM-MESSAGEID: 1770072160418154100 Content-Type: text/plain; charset="utf-8" The migration subsystem currently has code to merge two objects of the same type. It does so by checking which fields are present in a source object and overwriting the corresponding fields on the destination object. This leads to a lot of open-coded lines such as: if (src->has_foobar) { dst->foobar =3D src->foobar; } This pattern could be replaced by a copy using visitors. Implement a macro that extracts elements from a source object using an output visitor and merges it with a destination object using an input visitor. Acked-by: Peter Xu Signed-off-by: Fabiano Rosas --- include/qapi/type-helpers.h | 40 +++++++++++++++++++++++++++++++++++++ 1 file changed, 40 insertions(+) diff --git a/include/qapi/type-helpers.h b/include/qapi/type-helpers.h index fc8352cdec..f22d7b7139 100644 --- a/include/qapi/type-helpers.h +++ b/include/qapi/type-helpers.h @@ -10,6 +10,9 @@ */ =20 #include "qapi/qapi-types-common.h" +#include "qapi/qobject-input-visitor.h" +#include "qapi/qobject-output-visitor.h" +#include "qapi/dealloc-visitor.h" =20 HumanReadableText *human_readable_text_from_str(GString *str); =20 @@ -20,3 +23,40 @@ HumanReadableText *human_readable_text_from_str(GString = *str); * cleanup. */ char **strv_from_str_list(const strList *list); + +/* + * Merge @src over @dst by copying deep clones of the present members + * from @src to @dst. Non-present on @src are left untouched on + * @dst. Pointer members that are overwritten are also freed. + */ +#define QAPI_MERGE(type, dst_, src_) \ + ({ \ + QObject *out_ =3D NULL; \ + Visitor *v_; \ + /* read in from src */ \ + v_ =3D qobject_output_visitor_new(&out_); \ + visit_type_ ## type(v_, NULL, &src_, &error_abort); \ + visit_complete(v_, &out_); \ + visit_free(v_); \ + /* \ + * Free the memory for which the pointers will be overwritten \ + * in the next step. \ + */ \ + v_ =3D qapi_dealloc_present_visitor_new(out_); \ + visit_start_struct(v_, NULL, NULL, 0, &error_abort); \ + visit_type_ ## type ## _members(v_, dst_, &error_abort); \ + visit_end_struct(v_, NULL); \ + visit_free(v_); \ + /* \ + * Write to dst but leave existing fields intact (except for \ + * has_* which will be updated according to their presence in \ + * src). \ + */ \ + v_ =3D qobject_input_visitor_new(out_); \ + visit_start_struct(v_, NULL, NULL, 0, &error_abort); \ + visit_type_ ## type ## _members(v_, dst_, &error_abort); \ + visit_check_struct(v_, &error_abort); \ + visit_end_struct(v_, NULL); \ + visit_free(v_); \ + qobject_unref(out_); \ + }) --=20 2.51.0