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Re: [Qemu-devel] [PATCH v11 25/28] qapi: Simplify visits of optional fie
From: |
Markus Armbruster |
Subject: |
Re: [Qemu-devel] [PATCH v11 25/28] qapi: Simplify visits of optional fields |
Date: |
Thu, 12 Nov 2015 16:11:40 +0100 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/24.5 (gnu/linux) |
Eric Blake <address@hidden> writes:
> None of the visitor callbacks would set an error when testing
> if an optional field was present; make this part of the interface
> contract by eliminating the errp argument. Then, for less code,
> reflect the determined boolean value back to the caller instead
> of making the caller read the boolean after the fact.
>
> The resulting generated code has a nice diff:
>
> |- visit_optional(v, &has_fdset_id, "fdset-id", &err);
> |- if (err) {
> |- goto out;
> |- }
> |- if (has_fdset_id) {
> |+ if (visit_optional(v, &has_fdset_id, "fdset-id")) {
> | visit_type_int(v, &fdset_id, "fdset-id", &err);
> | if (err) {
> | goto out;
> | }
> | }
Any particular reason not to do
has_fdset_id = visit_optional(v, "fdset-id");
if (has_fdset_id) {
visit_type_int(v, &fdset_id, "fdset-id", &err);
if (err) {
goto out;
}
}
?
> Signed-off-by: Eric Blake <address@hidden>
>
> ---
> v11 (no v10): no change
> v9: no change
> v8: no change
> v7: rebase to no member.c_name()
> v6: rebase onto earlier testsuite and gen_err_check() improvements
> ---
> include/qapi/visitor-impl.h | 5 ++---
> include/qapi/visitor.h | 10 ++++++++--
> qapi/opts-visitor.c | 2 +-
> qapi/qapi-visit-core.c | 6 +++---
> qapi/qmp-input-visitor.c | 3 +--
> qapi/string-input-visitor.c | 3 +--
> scripts/qapi.py | 7 +------
> 7 files changed, 17 insertions(+), 19 deletions(-)
>
> diff --git a/include/qapi/visitor-impl.h b/include/qapi/visitor-impl.h
> index ac6c17e..81d1aa0 100644
> --- a/include/qapi/visitor-impl.h
> +++ b/include/qapi/visitor-impl.h
> @@ -44,9 +44,8 @@ struct Visitor
> void (*type_any)(Visitor *v, QObject **obj, const char *name,
> Error **errp);
>
> - /* May be NULL */
> - void (*optional)(Visitor *v, bool *present, const char *name,
> - Error **errp);
> + /* May be NULL; most useful for input visitors. */
> + void (*optional)(Visitor *v, bool *present, const char *name);
>
> void (*type_uint8)(Visitor *v, uint8_t *obj, const char *name, Error
> **errp);
> void (*type_uint16)(Visitor *v, uint16_t *obj, const char *name, Error
> **errp);
> diff --git a/include/qapi/visitor.h b/include/qapi/visitor.h
> index 250e8e1..dd4f0b3 100644
> --- a/include/qapi/visitor.h
> +++ b/include/qapi/visitor.h
> @@ -39,8 +39,14 @@ void visit_end_implicit_struct(Visitor *v, Error **errp);
> void visit_start_list(Visitor *v, const char *name, Error **errp);
> GenericList *visit_next_list(Visitor *v, GenericList **list, Error **errp);
> void visit_end_list(Visitor *v, Error **errp);
> -void visit_optional(Visitor *v, bool *present, const char *name,
> - Error **errp);
> +
> +/**
> + * Check if an optional member @name of an object needs visiting.
> + * For input visitors, set address@hidden according to whether the
> + * corresponding visit_type_*() needs calling; for other visitors,
> + * leave address@hidden unchanged. Return address@hidden for convenience.
> + */
> +bool visit_optional(Visitor *v, bool *present, const char *name);
>
> /**
> * Determine the qtype of the item @name in the current object visit.
> diff --git a/qapi/opts-visitor.c b/qapi/opts-visitor.c
> index cd10392..ef5fb8b 100644
> --- a/qapi/opts-visitor.c
> +++ b/qapi/opts-visitor.c
> @@ -488,7 +488,7 @@ opts_type_size(Visitor *v, uint64_t *obj, const char
> *name, Error **errp)
>
>
> static void
> -opts_optional(Visitor *v, bool *present, const char *name, Error **errp)
> +opts_optional(Visitor *v, bool *present, const char *name)
> {
> OptsVisitor *ov = DO_UPCAST(OptsVisitor, visitor, v);
>
> diff --git a/qapi/qapi-visit-core.c b/qapi/qapi-visit-core.c
> index 52c132a..daaa3af 100644
> --- a/qapi/qapi-visit-core.c
> +++ b/qapi/qapi-visit-core.c
> @@ -73,12 +73,12 @@ void visit_end_union(Visitor *v, bool data_present, Error
> **errp)
> }
> }
>
> -void visit_optional(Visitor *v, bool *present, const char *name,
> - Error **errp)
> +bool visit_optional(Visitor *v, bool *present, const char *name)
> {
> if (v->optional) {
> - v->optional(v, present, name, errp);
> + v->optional(v, present, name);
> }
> + return *present;
> }
Slightly ugly: struct Visitor method optional returns void, but the
wrapper returns bool.
>
> void visit_get_next_type(Visitor *v, QTypeCode *type, bool promote_int,
> diff --git a/qapi/qmp-input-visitor.c b/qapi/qmp-input-visitor.c
> index 4238faf..9f0ed69 100644
> --- a/qapi/qmp-input-visitor.c
> +++ b/qapi/qmp-input-visitor.c
> @@ -304,8 +304,7 @@ static void qmp_input_type_any(Visitor *v, QObject **obj,
> const char *name,
> *obj = qobj;
> }
>
> -static void qmp_input_optional(Visitor *v, bool *present, const char *name,
> - Error **errp)
> +static void qmp_input_optional(Visitor *v, bool *present, const char *name)
> {
> QmpInputVisitor *qiv = to_qiv(v);
> QObject *qobj = qmp_input_get_object(qiv, name, true);
> diff --git a/qapi/string-input-visitor.c b/qapi/string-input-visitor.c
> index bbd6a54..dee780a 100644
> --- a/qapi/string-input-visitor.c
> +++ b/qapi/string-input-visitor.c
> @@ -299,8 +299,7 @@ static void parse_type_number(Visitor *v, double *obj,
> const char *name,
> *obj = val;
> }
>
> -static void parse_optional(Visitor *v, bool *present, const char *name,
> - Error **errp)
> +static void parse_optional(Visitor *v, bool *present, const char *name)
> {
> StringInputVisitor *siv = DO_UPCAST(StringInputVisitor, visitor, v);
>
> diff --git a/scripts/qapi.py b/scripts/qapi.py
> index 1790e8f..b17f843 100644
> --- a/scripts/qapi.py
> +++ b/scripts/qapi.py
> @@ -1656,15 +1656,10 @@ def gen_visit_fields(members, prefix='',
> need_cast=False, skiperr=False):
> for memb in members:
> if memb.optional:
> ret += mcgen('''
> - visit_optional(v, &%(prefix)shas_%(c_name)s, "%(name)s", %(errp)s);
> + if (visit_optional(v, &%(prefix)shas_%(c_name)s, "%(name)s")) {
> ''',
> prefix=prefix, c_name=c_name(memb.name),
> name=memb.name, errp=errparg)
> - ret += gen_err_check(skiperr=skiperr)
> - ret += mcgen('''
> - if (%(prefix)shas_%(c_name)s) {
> -''',
> - prefix=prefix, c_name=c_name(memb.name))
> push_indent()
>
> # Ugly: sometimes we need to cast away const
- [Qemu-devel] [PATCH v11 15/28] qapi: Track owner of each object member, (continued)
- [Qemu-devel] [PATCH v11 15/28] qapi: Track owner of each object member, Eric Blake, 2015/11/11
- [Qemu-devel] [PATCH v11 16/28] qapi: Detect collisions in C member names, Eric Blake, 2015/11/11
- [Qemu-devel] [PATCH v11 20/28] qapi: Forbid case-insensitive clashes, Eric Blake, 2015/11/11
- [Qemu-devel] [PATCH v11 17/28] cpu: Convert CpuInfo into flat union, Eric Blake, 2015/11/11
- [Qemu-devel] [PATCH v11 24/28] qapi: Add positive tests to qapi-schema-test, Eric Blake, 2015/11/11
- [Qemu-devel] [PATCH v11 26/28] qapi: Move duplicate member checks to schema check(), Eric Blake, 2015/11/11
- [Qemu-devel] [PATCH v11 25/28] qapi: Simplify visits of optional fields, Eric Blake, 2015/11/11
- Re: [Qemu-devel] [PATCH v11 25/28] qapi: Simplify visits of optional fields,
Markus Armbruster <=
- [Qemu-devel] [PATCH v11 22/28] qapi: Simplify visiting of alternate types, Eric Blake, 2015/11/11
- [Qemu-devel] [PATCH v11 28/28] qapi: Detect base class loops, Eric Blake, 2015/11/11
- [Qemu-devel] [PATCH v11 23/28] qapi: Fix alternates that accept 'number' but not 'int', Eric Blake, 2015/11/11