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Diffstat (limited to 'docs/devel/qapi-code-gen.txt')
| -rw-r--r-- | docs/devel/qapi-code-gen.txt | 29 |
1 files changed, 29 insertions, 0 deletions
diff --git a/docs/devel/qapi-code-gen.txt b/docs/devel/qapi-code-gen.txt index 94a7e8f4d0..d3b0990983 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 |