qapi: Tighten the regex on valid names

We already documented that qapi names should match specific
patterns (such as starting with a letter unless it was an enum
value or a downstream extension).  Tighten that from a suggestion
into a hard requirement, which frees up names beginning with a
single underscore for qapi internal usage.

The tighter regex doesn't forbid everything insane that a user
could provide (for example, a user could name a type 'Foo-lookup'
to collide with the generated 'Foo_lookup[]' for an enum 'Foo'),
but does a good job at protecting the most obvious uses, and
also happens to reserve single leading underscore for later use.

The handling of enum values starting with a digit is tricky:
commit 9fb081e introduced a subtle bug by using c_name() on
a munged value, which would allow an enum to include the
member 'q-int' in spite of our reservation.  Furthermore,
munging with a leading '_' would fail our tighter regex.  So
fix it by only munging for leading digits (which are never
ticklish in c_name()) and by using a different prefix (I
picked 'D', although any letter should do).

Add new tests, reserved-member-underscore and reserved-enum-q,
to demonstrate the tighter checking.

Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1447836791-369-22-git-send-email-eblake@redhat.com>
Message-Id: <1447883135-18020-1-git-send-email-eblake@redhat.com>
[Eric's fixup squashed in]
Signed-off-by: Markus Armbruster <armbru@redhat.com>

1 files changed, 11 insertions, 11 deletions

diff --git a/docs/qapi-code-gen.txt b/docs/qapi-code-gen.txt
index ceb9a782d0..32cc68fff1 100644
--- a/docs/qapi-code-gen.txt
+++ b/docs/qapi-code-gen.txt
@@ -118,17 +118,17 @@ tracking optional fields.
 
 Any name (command, event, type, field, or enum value) beginning with
 "x-" is marked experimental, and may be withdrawn or changed
-incompatibly in a future release.  Downstream vendors may add
-extensions; such extensions should begin with a prefix matching
-"__RFQDN_" (for the reverse-fully-qualified-domain-name of the
-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.
-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.
+incompatibly in a future release.  All names must begin with a letter,
+and contain only ASCII letters, digits, dash, and underscore.  There
+are two exceptions: enum values may start with a digit, and any
+extensions added by downstream vendors should start with a prefix
+matching "__RFQDN_" (for the reverse-fully-qualified-domain-name of
+the vendor), even if the rest of the name uses dash (example:
+__com.redhat_drive-mirror).  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