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authorEric Blake <eblake@redhat.com>2015-10-26 16:34:44 -0600
committerMarkus Armbruster <armbru@redhat.com>2015-11-02 08:30:26 +0100
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treec19eeaa3eed47ee66a97a4c14a421c61e2055ff6 /docs
parent255960dd374d4497d6ea537305f1b0d8a3433789 (diff)
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qapi: Reserve 'q_*' and 'has_*' member names
c_name() produces names starting with 'q_' when protecting a dictionary member name that would fail to directly compile, but in doing so can cause clashes with any member name already beginning with 'q-' or 'q_'. Likewise, we create a C name 'has_' for any optional member that can clash with any member name beginning with 'has-' or 'has_'. Technically, rather than blindly reserving the namespace, we could try to complain about user names only when an actual collision occurs, or even teach c_name() how to munge names to avoid collisions. But it is not trivial, especially when collisions can occur across multiple types (such as via inheritance or flat unions). Besides, no existing .json files are trying to use these names. So it's easier to just outright forbid the potential for collision. We can always relax things in the future if a real need arises for QMP to express member names that have been forbidden here. 'has_' only has to be reserved for struct/union member names, while 'q_' is reserved everywhere (matching the fact that only members can be optional, while we use c_name() for munging both members and entities). Note that we could relax 'q_' restrictions on entities independently from member names; for example, c_name('qmp_' + 'unix') would result in a different function name than our current 'qmp_' + c_name('unix'). Update and add tests to cover the new error messages. Signed-off-by: Eric Blake <eblake@redhat.com> Message-Id: <1445898903-12082-6-git-send-email-eblake@redhat.com> [Consistently pass protect=False to c_name(); commit message tweaked slightly] Signed-off-by: Markus Armbruster <armbru@redhat.com>
Diffstat (limited to 'docs')
-rw-r--r--docs/qapi-code-gen.txt11
1 files changed, 7 insertions, 4 deletions
diff --git a/docs/qapi-code-gen.txt b/docs/qapi-code-gen.txt
index c4264a8..4d8c2fc 100644
--- a/docs/qapi-code-gen.txt
+++ b/docs/qapi-code-gen.txt
@@ -112,7 +112,9 @@ and field names within a type, should be all lower case with words
separated by a hyphen. However, some existing older commands and
complex types use underscore; when extending such expressions,
consistency is preferred over blindly avoiding underscore. Event
-names should be ALL_CAPS with words separated by underscore.
+names should be ALL_CAPS with words separated by underscore. Field
+names cannot start with 'has-' or 'has_', as this is reserved for
+tracking optional fields.
Any name (command, event, type, field, or enum value) beginning with
"x-" is marked experimental, and may be withdrawn or changed
@@ -123,9 +125,10 @@ vendor), even if the rest of the name uses dash (example:
__com.redhat_drive-mirror). Other than downstream extensions (with
leading underscore and the use of dots), all names should begin with a
letter, and contain only ASCII letters, digits, dash, and underscore.
-It is okay to reuse names that match C keywords; the generator will
-rename a field named "default" in the QAPI to "q_default" in the
-generated C code.
+Names beginning with 'q_' are reserved for the generator: QMP names
+that resemble C keywords or other problematic strings will be munged
+in C to use this prefix. For example, a field named "default" in
+qapi becomes "q_default" in the generated C code.
In the rest of this document, usage lines are given for each
expression type, with literal strings written in lower case and