From 800877bb1639d38ffaebe312a37b61c66bb10c83 Mon Sep 17 00:00:00 2001 From: Anton Nefedov Date: Mon, 18 Jun 2018 11:40:05 +0300 Subject: qapi: allow empty branches in flat unions It often happens that just a few discriminator values imply extra data in a flat union. Existing checks did not make possible to leave other values uncovered. Such cases had to be worked around by either stating a dummy (empty) type or introducing another (subset) discriminator enumeration. Both options create redundant entities in qapi files for little profit. With this patch it is not necessary anymore to add designated union fields for every possible value of a discriminator enumeration. Signed-off-by: Anton Nefedov Message-Id: <1529311206-76847-2-git-send-email-anton.nefedov@virtuozzo.com> Reviewed-by: Markus Armbruster Signed-off-by: Markus Armbruster --- docs/devel/qapi-code-gen.txt | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) (limited to 'docs') diff --git a/docs/devel/qapi-code-gen.txt b/docs/devel/qapi-code-gen.txt index 1366228..88a70e4 100644 --- a/docs/devel/qapi-code-gen.txt +++ b/docs/devel/qapi-code-gen.txt @@ -496,9 +496,11 @@ Resulting in these JSON objects: Notice that in a flat union, the discriminator name is controlled by the user, but because it must map to a base member with enum type, the -code generator can ensure that branches exist for all values of the -enum (although the order of the keys need not match the declaration of -the enum). In the resulting generated C data types, a flat union is +code generator ensures that branches match the existing values of the +enum. The order of the keys need not match the declaration of the enum. +The keys need not cover all possible enum values. Omitted enum values +are still valid branches that add no additional members to the data type. +In the resulting generated C data types, a flat union is represented as a struct with the base members included directly, and then a union of structures for each branch of the struct. -- cgit v1.1