From 967c885108f18e5065744719f7959ba5ea0a5b0d Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Marc-Andr=C3=A9=20Lureau?= Date: Tue, 3 Jul 2018 17:56:35 +0200 Subject: qapi: add 'if' to top-level expressions MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Accept 'if' key in top-level elements, accepted as string or list of string type. The following patches will modify the test visitor to check the value is correctly saved, and generate #if/#endif code (as a single #if/endif line or a series for a list). Example of 'if' key: { 'struct': 'TestIfStruct', 'data': { 'foo': 'int' }, 'if': 'defined(TEST_IF_STRUCT)' } The generated code is for now *unconditional*. Later patches generate the conditionals. Signed-off-by: Marc-André Lureau Reviewed-by: Markus Armbruster Message-Id: <20180703155648.11933-2-marcandre.lureau@redhat.com> [Commit message and Documentation improved] Signed-off-by: Markus Armbruster --- docs/devel/qapi-code-gen.txt | 29 +++++++++++++++++++++++++++++ 1 file changed, 29 insertions(+) (limited to 'docs') diff --git a/docs/devel/qapi-code-gen.txt b/docs/devel/qapi-code-gen.txt index 94a7e8f..d3b0990 100644 --- a/docs/devel/qapi-code-gen.txt +++ b/docs/devel/qapi-code-gen.txt @@ -744,6 +744,35 @@ Example: Red Hat, Inc. controls redhat.com, and may therefore add a downstream command __com.redhat_drive-mirror. +=== Configuring the schema === + +The 'struct', 'enum', 'union', 'alternate', 'command' and 'event' +top-level expressions can take an 'if' key. Its value must be a string +or a list of strings. A string is shorthand for a list containing just +that string. The code generated for the top-level expression will then +be guarded by #if COND for each COND in the list. + +Example: a conditional struct + + { 'struct': 'IfStruct', 'data': { 'foo': 'int' }, + 'if': ['defined(CONFIG_FOO)', 'defined(HAVE_BAR)'] } + +gets its generated code guarded like this: + + #if defined(CONFIG_FOO) + #if defined(HAVE_BAR) + ... generated code ... + #endif /* defined(HAVE_BAR) */ + #endif /* defined(CONFIG_FOO) */ + +Please note that you are responsible to ensure that the C code will +compile with an arbitrary combination of conditions, since the +generators are unable to check it at this point. + +The presence of 'if' keys in the schema is reflected through to the +introspection output depending on the build configuration. + + == Client JSON Protocol introspection == Clients of a Client JSON Protocol commonly need to figure out what -- cgit v1.1