| Message ID | 1460131992-32278-19-git-send-email-eblake@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Eric Blake <eblake@redhat.com> writes: > We have two uses of list visits in the entire code base: one in > spapr_drc (which completely avoids visit_next_list(), feeding in > integers from a different source than uint8List), and one in > qapi-visit.py Period here, convert the parenthesis to a sentence. > (that is, all other list visitors are generated > in qapi-visit.c, and share the same paradigm based on a qapi > FooList type). The above reviews existing uses. Next, you show that visit_next_list() semantics are awkward. Suggest to start with the awkward semantics, and only then review existing uses. > What's more, the semantics of the list visit are > somewhat baroque, with the following pseudocode when FooList is > used: > > start() > for (prev = head; cur = next(prev); prev = &cur) { > visit(&cur->value) > } > > Note that these semantics (advance before visit) requires that > the first call to next() return the list head, while all other > calls return the next element of the list; that is, every visitor > implementation is required to track extra state to decide whether > to return the input as-is, or to advance. It also requires an > argument of 'GenericList **' to next(), solely because the first > iteration might need to modify the caller's GenericList head, so > that all other calls have to do a layer of dereferencing. > > We can greatly simplify things by hoisting the special case > into the start() routine, and flipping the order in the loop > to visit before advance: > > start(head) > for (tail = *head; tail; tail = next(tail)) { > visit(&tail->value) > } > > With the simpler semantics, visitors have less state to track, > the argument to next() is reduced to 'GenericList *', and it > also becomes obvious whether an input visitor is allocating a > FooList during visit_start_list() (rather than the old way of > not knowing if an allocation happened until the first > visit_next_list()). Minor drawback: we now allocate both in start_list() and in next_list(). Minor, because the allocation is trivial. > The signature of visit_start_list() is chosen to match > visit_start_struct(), with the new parameters after 'name'. Good idea. > The spapr_drc case is a virtual visit, done by passing NULL for > list, similarly to how NULL is passed to visit_start_struct() > when a qapi type is not used in those visits. It was easy to > provide these semantics for qmp-output and dealloc visitors, > and a bit harder for qmp-input (several prerequisite patches > refactored things to make this patch straightforward). But it > turned out that the string and opts visitors munge enough other > state during visit_next_list() to make it easier to just > document and require a GenericList visit for now; an assertion > will remind us to adjust things if we need the semantics in the > future. > > Signed-off-by: Eric Blake <eblake@redhat.com> > > --- > v14: no change > v13: documentation wording tweaks > v12: rebase to earlier changes, drop R-b, improve documentation, > split out qmp-input cleanups into prereq patches > [no v10, v11] > v9: no change > v8: consistent parameter order, fix qmp_input_get_next_type() to not > skip list entries > v7: new patch > --- > include/qapi/visitor.h | 47 +++++++++++++++++++----------------- > include/qapi/visitor-impl.h | 7 +++--- > scripts/qapi-visit.py | 18 +++++++------- > include/qapi/opts-visitor.h | 2 +- > include/qapi/string-input-visitor.h | 3 ++- > include/qapi/string-output-visitor.h | 3 ++- > qapi/qapi-visit-core.c | 12 +++++---- > hw/ppc/spapr_drc.c | 2 +- > qapi/opts-visitor.c | 33 +++++++++++-------------- > qapi/qapi-dealloc-visitor.c | 35 ++++++--------------------- > qapi/qmp-input-visitor.c | 32 ++++++++++++------------ > qapi/qmp-output-visitor.c | 22 ++++------------- > qapi/string-input-visitor.c | 36 +++++++++++++-------------- > qapi/string-output-visitor.c | 41 +++++++++++-------------------- > docs/qapi-code-gen.txt | 17 +++++++------ > 15 files changed, 133 insertions(+), 177 deletions(-) > > diff --git a/include/qapi/visitor.h b/include/qapi/visitor.h > index e1213a3..a22a7ce 100644 > --- a/include/qapi/visitor.h > +++ b/include/qapi/visitor.h > @@ -165,7 +165,7 @@ > * if (err) { > * goto outobj; > * } > - * visit_start_list(v, "list", &err); > + * visit_start_list(v, "list", NULL, 0, &err); > * if (err) { > * goto outobj; > * } > @@ -268,40 +268,43 @@ void visit_end_struct(Visitor *v); > * @name expresses the relationship of this list to its parent > * container; see the general description of @name above. > * > + * @list must be non-NULL for a real walk, in which case @size > + * determines how much memory an input visitor will allocate into > + * *@list (at least sizeof(GenericList)). Some visitors also allow > + * @list to be NULL for a virtual walk, in which case @size is > + * ignored. > + * > * @errp must be NULL-initialized, and is set if an error is detected > * (such as if a member @name is not present, or is present but not a > - * list). > + * list). On error, input visitors set *@obj to NULL. I guess you copied this from visit_start_struct(), which only makes sense. Except the thing is called @list here. More of the same below. > * > * After visit_start_list() succeeds, the caller may visit its members > - * one after the other. A real visit uses visit_next_list() for > - * traversing the linked list, while a virtual visit uses other means. > - * For each list element, call the appropriate visit_type_FOO() with > - * name set to NULL and obj set to the address of the value member of > - * the list element. Finally, visit_end_list() needs to be called to > - * clean up, even if intermediate visits fail. See the examples > - * above. > + * one after the other. A real visit (where @obj is non-NULL) uses > + * visit_next_list() for traversing the linked list, while a virtual > + * visit (where @obj is NULL) uses other means. For each list > + * element, call the appropriate visit_type_FOO() with name set to > + * NULL and obj set to the address of the value member of the list > + * element. Finally, visit_end_list() needs to be called to clean up, > + * even if intermediate visits fail. See the examples above. > */ > -void visit_start_list(Visitor *v, const char *name, Error **errp); > +void visit_start_list(Visitor *v, const char *name, GenericList **list, > + size_t size, Error **errp); > > /* > - * Iterate over a GenericList during a list visit. > + * Iterate over a GenericList during a non-virtual list visit. Is "non-virtual" new in this patch? If not, is this the right patch to insert it? > * > - * @size represents the size of a linked list node. > + * @size represents the size of a linked list node (at least > + * sizeof(GenericList)). Likewise. > * > - * @list must not be NULL; on the first call, @list contains the > - * address of the list head, and on subsequent calls *@list must be > - * the previously returned value. Must be called in a loop until a > + * @tail must not be NULL; on the first call, @tail is the value of > + * *list after visit_start_list(), and on subsequent calls @tail must > + * be the previously returned value. Must be called in a loop until a > * NULL return or error occurs; for each non-NULL return, the caller > * must then call the appropriate visit_type_*() for the element type > * of the list, with that function's name parameter set to NULL and > - * obj set to the address of (*@list)->value. > - * > - * FIXME: This interface is awkward; it requires all callbacks to > - * track whether it is the first or a subsequent call. A better > - * interface would pass the head of the list through > - * visit_start_list(). > + * obj set to the address of @tail->value. > */ > -GenericList *visit_next_list(Visitor *v, GenericList **list, size_t size); > +GenericList *visit_next_list(Visitor *v, GenericList *tail, size_t size); > > /* > * Complete a list visit started earlier. > diff --git a/include/qapi/visitor-impl.h b/include/qapi/visitor-impl.h > index d44fcd1..0471465 100644 > --- a/include/qapi/visitor-impl.h > +++ b/include/qapi/visitor-impl.h > @@ -45,11 +45,12 @@ struct Visitor > /* Must be set to visit structs. */ > void (*end_struct)(Visitor *v); > > - /* Must be set. */ > - void (*start_list)(Visitor *v, const char *name, Error **errp); > + /* Must be set; document if @list may not be NULL. */ Too terse, I'm afraid. Suggest something like "implementations may require @list to be non-null, but must document it." > + void (*start_list)(Visitor *v, const char *name, GenericList **list, > + size_t size, Error **errp); > > /* Must be set. */ > - GenericList *(*next_list)(Visitor *v, GenericList **list, size_t size); > + GenericList *(*next_list)(Visitor *v, GenericList *tail, size_t size); > > /* Must be set. */ > void (*end_list)(Visitor *v); > diff --git a/scripts/qapi-visit.py b/scripts/qapi-visit.py > index bfe4a09..69f0133 100644 > --- a/scripts/qapi-visit.py > +++ b/scripts/qapi-visit.py > @@ -117,20 +117,20 @@ def gen_visit_list(name, element_type): > void visit_type_%(c_name)s(Visitor *v, const char *name, %(c_name)s **obj, Error **errp) > { > Error *err = NULL; > - GenericList *i, **prev; > + %(c_name)s *tail; > + size_t size = sizeof(**obj); > > - visit_start_list(v, name, &err); > + visit_start_list(v, name, (GenericList **)obj, size, &err); > if (err) { > goto out; > } > - > - for (prev = (GenericList **)obj; > - !err && (i = visit_next_list(v, prev, sizeof(**obj))) != NULL; > - prev = &i) { > - %(c_name)s *native_i = (%(c_name)s *)i; > - visit_type_%(c_elt_type)s(v, NULL, &native_i->value, &err); > + for (tail = *obj; tail; > + tail = (%(c_name)s *)visit_next_list(v, (GenericList *)tail, size)) { > + visit_type_%(c_elt_type)s(v, NULL, &tail->value, &err); > + if (err) { > + break; > + } > } > - Keep the blank lines around the loop? > visit_end_list(v); > out: > error_propagate(errp, err); > diff --git a/include/qapi/opts-visitor.h b/include/qapi/opts-visitor.h > index 3fcd327..7c9a7e5 100644 > --- a/include/qapi/opts-visitor.h > +++ b/include/qapi/opts-visitor.h > @@ -32,7 +32,7 @@ typedef struct OptsVisitor OptsVisitor; > * > * The Opts input visitor does not yet implement support for visiting > * QAPI alternates, numbers (other than integers), null, or arbitrary > - * QTypes. > + * QTypes. It also requires non-NULL list to visit_start_list(). non-null list argument to > */ > OptsVisitor *opts_visitor_new(const QemuOpts *opts); > void opts_visitor_cleanup(OptsVisitor *nv); > diff --git a/include/qapi/string-input-visitor.h b/include/qapi/string-input-visitor.h > index 1a34c52..d26a845 100644 > --- a/include/qapi/string-input-visitor.h > +++ b/include/qapi/string-input-visitor.h > @@ -19,7 +19,8 @@ typedef struct StringInputVisitor StringInputVisitor; > > /* > * The string input visitor does not yet implement support for > - * visiting QAPI structs, alternates, null, or arbitrary QTypes. > + * visiting QAPI structs, alternates, null, or arbitrary QTypes. It > + * also requires non-NULL list to visit_start_list(). Likewise. > */ > StringInputVisitor *string_input_visitor_new(const char *str); > void string_input_visitor_cleanup(StringInputVisitor *v); > diff --git a/include/qapi/string-output-visitor.h b/include/qapi/string-output-visitor.h > index 2564833..0a9354c 100644 > --- a/include/qapi/string-output-visitor.h > +++ b/include/qapi/string-output-visitor.h > @@ -19,7 +19,8 @@ typedef struct StringOutputVisitor StringOutputVisitor; > > /* > * The string output visitor does not yet implement support for > - * visiting QAPI structs, alternates, null, or arbitrary QTypes. > + * visiting QAPI structs, alternates, null, or arbitrary QTypes. It > + * also requires non-NULL list to visit_start_list(). Likewise. > */ > StringOutputVisitor *string_output_visitor_new(bool human); > void string_output_visitor_cleanup(StringOutputVisitor *v); > diff --git a/qapi/qapi-visit-core.c b/qapi/qapi-visit-core.c > index 76ea690..622b315 100644 > --- a/qapi/qapi-visit-core.c > +++ b/qapi/qapi-visit-core.c > @@ -42,15 +42,17 @@ void visit_end_struct(Visitor *v) > v->end_struct(v); > } > > -void visit_start_list(Visitor *v, const char *name, Error **errp) > +void visit_start_list(Visitor *v, const char *name, GenericList **list, > + size_t size, Error **errp) > { > - v->start_list(v, name, errp); > + assert(!list || size >= sizeof(GenericList)); > + v->start_list(v, name, list, size, errp); > } > > -GenericList *visit_next_list(Visitor *v, GenericList **list, size_t size) > +GenericList *visit_next_list(Visitor *v, GenericList *tail, size_t size) > { > - assert(list && size >= sizeof(GenericList)); > - return v->next_list(v, list, size); > + assert(tail && size >= sizeof(GenericList)); > + return v->next_list(v, tail, size); > } > > void visit_end_list(Visitor *v) > diff --git a/hw/ppc/spapr_drc.c b/hw/ppc/spapr_drc.c > index 5395c02..dd3c502 100644 > --- a/hw/ppc/spapr_drc.c > +++ b/hw/ppc/spapr_drc.c > @@ -309,7 +309,7 @@ static void prop_get_fdt(Object *obj, Visitor *v, const char *name, > int i; > prop = fdt_get_property_by_offset(fdt, fdt_offset, &prop_len); > name = fdt_string(fdt, fdt32_to_cpu(prop->nameoff)); > - visit_start_list(v, name, &err); > + visit_start_list(v, name, NULL, 0, &err); > if (err) { > error_propagate(errp, err); > return; > diff --git a/qapi/opts-visitor.c b/qapi/opts-visitor.c > index a08d5a7..6d572cc 100644 > --- a/qapi/opts-visitor.c > +++ b/qapi/opts-visitor.c > @@ -23,9 +23,8 @@ > enum ListMode > { > LM_NONE, /* not traversing a list of repeated options */ > - LM_STARTED, /* opts_start_list() succeeded */ > > - LM_IN_PROGRESS, /* opts_next_list() has been called. > + LM_IN_PROGRESS, /* opts_next_list() ready to be called. > * > * Generating the next list link will consume the most > * recently parsed QemuOpt instance of the repeated > @@ -214,35 +213,33 @@ lookup_distinct(const OptsVisitor *ov, const char *name, Error **errp) > > > static void > -opts_start_list(Visitor *v, const char *name, Error **errp) > +opts_start_list(Visitor *v, const char *name, GenericList **list, size_t size, > + Error **errp) > { > OptsVisitor *ov = to_ov(v); > > /* we can't traverse a list in a list */ > assert(ov->list_mode == LM_NONE); > + /* we don't support visits without GenericList, yet */ without a list Do we plan to support them? If not, scratch "yet". > + assert(list); > ov->repeated_opts = lookup_distinct(ov, name, errp); > - if (ov->repeated_opts != NULL) { > - ov->list_mode = LM_STARTED; > + if (ov->repeated_opts) { > + ov->list_mode = LM_IN_PROGRESS; > + *list = g_malloc0(size); > + } else { > + *list = NULL; > } > } > > > static GenericList * > -opts_next_list(Visitor *v, GenericList **list, size_t size) > +opts_next_list(Visitor *v, GenericList *tail, size_t size) > { > OptsVisitor *ov = to_ov(v); > - GenericList **link; > > switch (ov->list_mode) { > - case LM_STARTED: > - ov->list_mode = LM_IN_PROGRESS; > - link = list; > - break; > - > case LM_SIGNED_INTERVAL: > case LM_UNSIGNED_INTERVAL: > - link = &(*list)->next; > - > if (ov->list_mode == LM_SIGNED_INTERVAL) { > if (ov->range_next.s < ov->range_limit.s) { > ++ov->range_next.s; > @@ -263,7 +260,6 @@ opts_next_list(Visitor *v, GenericList **list, size_t size) > g_hash_table_remove(ov->unprocessed_opts, opt->name); > return NULL; > } > - link = &(*list)->next; > break; > } > > @@ -271,8 +267,8 @@ opts_next_list(Visitor *v, GenericList **list, size_t size) > abort(); > } > > - *link = g_malloc0(size); > - return *link; > + tail->next = g_malloc0(size); > + return tail->next; > } > > > @@ -281,8 +277,7 @@ opts_end_list(Visitor *v) > { > OptsVisitor *ov = to_ov(v); > > - assert(ov->list_mode == LM_STARTED || > - ov->list_mode == LM_IN_PROGRESS || > + assert(ov->list_mode == LM_IN_PROGRESS || > ov->list_mode == LM_SIGNED_INTERVAL || > ov->list_mode == LM_UNSIGNED_INTERVAL); > ov->repeated_opts = NULL; > diff --git a/qapi/qapi-dealloc-visitor.c b/qapi/qapi-dealloc-visitor.c > index 9005bad..cd68b55 100644 > --- a/qapi/qapi-dealloc-visitor.c > +++ b/qapi/qapi-dealloc-visitor.c > @@ -22,7 +22,6 @@ > typedef struct StackEntry > { > void *value; > - bool is_list_head; > QTAILQ_ENTRY(StackEntry) node; > } StackEntry; > > @@ -43,10 +42,6 @@ static void qapi_dealloc_push(QapiDeallocVisitor *qov, void *value) > > e->value = value; > > - /* see if we're just pushing a list head tracker */ > - if (value == NULL) { > - e->is_list_head = true; > - } > QTAILQ_INSERT_HEAD(&qov->stack, e, node); > } > > @@ -93,38 +88,22 @@ static void qapi_dealloc_end_alternate(Visitor *v) > } > } > > -static void qapi_dealloc_start_list(Visitor *v, const char *name, Error **errp) > +static void qapi_dealloc_start_list(Visitor *v, const char *name, > + GenericList **list, size_t size, > + Error **errp) > { > - QapiDeallocVisitor *qov = to_qov(v); > - qapi_dealloc_push(qov, NULL); > } > > -static GenericList *qapi_dealloc_next_list(Visitor *v, GenericList **listp, > +static GenericList *qapi_dealloc_next_list(Visitor *v, GenericList *tail, > size_t size) > { > - GenericList *list = *listp; > - QapiDeallocVisitor *qov = to_qov(v); > - StackEntry *e = QTAILQ_FIRST(&qov->stack); > - > - if (e && e->is_list_head) { > - e->is_list_head = false; > - return list; > - } > - > - if (list) { > - list = list->next; > - g_free(*listp); > - return list; > - } > - > - return NULL; > + GenericList *next = tail->next; > + g_free(tail); > + return next; > } > > static void qapi_dealloc_end_list(Visitor *v) > { > - QapiDeallocVisitor *qov = to_qov(v); > - void *obj = qapi_dealloc_pop(qov); > - assert(obj == NULL); /* should've been list head tracker with no payload */ > } > One step closer to killing the stack. > static void qapi_dealloc_type_str(Visitor *v, const char *name, char **obj, > diff --git a/qapi/qmp-input-visitor.c b/qapi/qmp-input-visitor.c > index 16f2f5a..5360744 100644 > --- a/qapi/qmp-input-visitor.c > +++ b/qapi/qmp-input-visitor.c > @@ -29,8 +29,6 @@ typedef struct StackObject > > /* If obj is list: tail of list still needing visits */ > const QListEntry *entry; > - /* If obj is list: true if head is not visited yet */ > - bool first; > > GHashTable *h; /* If obj is dict: remaining keys needing visits */ > } StackObject; > @@ -87,7 +85,6 @@ static QObject *qmp_input_get_object(QmpInputVisitor *qiv, > assert(!name); > > if (tos->entry) { > - assert(!tos->first); > qobj = qlist_entry_obj(tos->entry); > if (consume) { > tos->entry = qlist_next(tos->entry); > @@ -117,7 +114,6 @@ static void qmp_input_push(QmpInputVisitor *qiv, QObject *obj, > > tos->obj = obj; > tos->entry = entry; > - tos->first = true; > tos->h = NULL; > > if (qiv->strict && qobject_type(obj) == QTYPE_QDICT) { > @@ -194,13 +190,17 @@ static void qmp_input_start_struct(Visitor *v, const char *name, void **obj, > } > > > -static void qmp_input_start_list(Visitor *v, const char *name, Error **errp) > +static void qmp_input_start_list(Visitor *v, const char *name, > + GenericList **list, size_t size, Error **errp) > { > QmpInputVisitor *qiv = to_qiv(v); > QObject *qobj = qmp_input_get_object(qiv, name, true); > const QListEntry *entry; > > if (!qobj || qobject_type(qobj) != QTYPE_QLIST) { > + if (list) { > + *list = NULL; > + } > error_setg(errp, QERR_INVALID_PARAMETER_TYPE, name ? name : "null", > "list"); > return; > @@ -208,28 +208,26 @@ static void qmp_input_start_list(Visitor *v, const char *name, Error **errp) > > entry = qlist_first(qobject_to_qlist(qobj)); > qmp_input_push(qiv, qobj, entry, errp); > + if (list) { > + if (entry) { > + *list = g_malloc0(size); > + } else { > + *list = NULL; > + } > + } > } > > -static GenericList *qmp_input_next_list(Visitor *v, GenericList **list, > +static GenericList *qmp_input_next_list(Visitor *v, GenericList *tail, > size_t size) > { > QmpInputVisitor *qiv = to_qiv(v); > - GenericList *entry; > StackObject *so = &qiv->stack[qiv->nb_stack - 1]; > > if (!so->entry) { > return NULL; > } > - > - entry = g_malloc0(size); > - if (so->first) { > - *list = entry; > - so->first = false; > - } else { > - (*list)->next = entry; > - } > - > - return entry; > + tail->next = g_malloc0(size); > + return tail->next; > } > > > diff --git a/qapi/qmp-output-visitor.c b/qapi/qmp-output-visitor.c > index ecb2005..40657be 100644 > --- a/qapi/qmp-output-visitor.c > +++ b/qapi/qmp-output-visitor.c > @@ -22,7 +22,6 @@ > typedef struct QStackEntry > { > QObject *value; > - bool is_list_head; > QTAILQ_ENTRY(QStackEntry) node; > } QStackEntry; > > @@ -52,9 +51,6 @@ static void qmp_output_push_obj(QmpOutputVisitor *qov, QObject *value) > assert(qov->root); > assert(value); > e->value = value; > - if (qobject_type(e->value) == QTYPE_QLIST) { > - e->is_list_head = true; > - } > QTAILQ_INSERT_HEAD(&qov->stack, e, node); > } > > @@ -120,7 +116,9 @@ static void qmp_output_end_struct(Visitor *v) > assert(qobject_type(value) == QTYPE_QDICT); > } > > -static void qmp_output_start_list(Visitor *v, const char *name, Error **errp) > +static void qmp_output_start_list(Visitor *v, const char *name, > + GenericList **listp, size_t size, > + Error **errp) > { > QmpOutputVisitor *qov = to_qov(v); > QList *list = qlist_new(); > @@ -129,20 +127,10 @@ static void qmp_output_start_list(Visitor *v, const char *name, Error **errp) > qmp_output_push(qov, list); > } > > -static GenericList *qmp_output_next_list(Visitor *v, GenericList **listp, > +static GenericList *qmp_output_next_list(Visitor *v, GenericList *tail, > size_t size) > { > - GenericList *list = *listp; > - QmpOutputVisitor *qov = to_qov(v); > - QStackEntry *e = QTAILQ_FIRST(&qov->stack); > - > - assert(e); > - if (e->is_list_head) { > - e->is_list_head = false; > - return list; > - } > - > - return list ? list->next : NULL; > + return tail->next; > } > > static void qmp_output_end_list(Visitor *v) > diff --git a/qapi/string-input-visitor.c b/qapi/string-input-visitor.c > index 797973a..77dd1a7 100644 > --- a/qapi/string-input-visitor.c > +++ b/qapi/string-input-visitor.c > @@ -25,8 +25,6 @@ struct StringInputVisitor > { > Visitor visitor; > > - bool head; > - > GList *ranges; > GList *cur_range; > int64_t cur; > @@ -125,11 +123,21 @@ error: > } > > static void > -start_list(Visitor *v, const char *name, Error **errp) > +start_list(Visitor *v, const char *name, GenericList **list, size_t size, > + Error **errp) > { > StringInputVisitor *siv = to_siv(v); > + Error *err = NULL; > > - parse_str(siv, errp); > + /* We don't support visits without a GenericList, yet */ without a list Do we plan to support them? If not, scratch "yet". > + assert(list); > + > + parse_str(siv, &err); > + if (err) { > + *list = NULL; > + error_propagate(errp, err); > + return; > + } > > siv->cur_range = g_list_first(siv->ranges); > if (siv->cur_range) { > @@ -137,13 +145,15 @@ start_list(Visitor *v, const char *name, Error **errp) > if (r) { > siv->cur = r->begin; > } > + *list = g_malloc0(size); > + } else { > + *list = NULL; > } > } > > -static GenericList *next_list(Visitor *v, GenericList **list, size_t size) > +static GenericList *next_list(Visitor *v, GenericList *tail, size_t size) > { > StringInputVisitor *siv = to_siv(v); > - GenericList **link; > Range *r; > > if (!siv->ranges || !siv->cur_range) { > @@ -167,21 +177,12 @@ static GenericList *next_list(Visitor *v, GenericList **list, size_t size) > siv->cur = r->begin; > } > > - if (siv->head) { > - link = list; > - siv->head = false; > - } else { > - link = &(*list)->next; > - } > - > - *link = g_malloc0(size); > - return *link; > + tail->next = g_malloc0(size); > + return tail->next; > } > > static void end_list(Visitor *v) > { > - StringInputVisitor *siv = to_siv(v); > - siv->head = true; > } > > static void parse_type_int64(Visitor *v, const char *name, int64_t *obj, > @@ -362,6 +363,5 @@ StringInputVisitor *string_input_visitor_new(const char *str) > v->visitor.optional = parse_optional; > > v->string = str; > - v->head = true; > return v; > } > diff --git a/qapi/string-output-visitor.c b/qapi/string-output-visitor.c > index 0d44d7e..e27e2df 100644 > --- a/qapi/string-output-visitor.c > +++ b/qapi/string-output-visitor.c > @@ -20,7 +20,7 @@ > > enum ListMode { > LM_NONE, /* not traversing a list of repeated options */ > - LM_STARTED, /* start_list() succeeded */ > + LM_STARTED, /* start_list() succeeded with multiple elements */ In opts-visitor.c, the comment says "opts_next_list() ready to be called". Any reason for the difference? > > LM_IN_PROGRESS, /* next_list() has been called. > * > @@ -48,7 +48,7 @@ enum ListMode { > > LM_UNSIGNED_INTERVAL,/* Same as above, only for an unsigned interval. */ > > - LM_END > + LM_END, /* next_list() called, about to see last element. */ > }; > > typedef enum ListMode ListMode; > @@ -58,7 +58,6 @@ struct StringOutputVisitor > Visitor visitor; > bool human; > GString *string; > - bool head; > ListMode list_mode; > union { > int64_t s; > @@ -266,39 +265,29 @@ static void print_type_number(Visitor *v, const char *name, double *obj, > } > > static void > -start_list(Visitor *v, const char *name, Error **errp) > +start_list(Visitor *v, const char *name, GenericList **list, size_t size, > + Error **errp) > { > StringOutputVisitor *sov = to_sov(v); > > /* we can't traverse a list in a list */ > assert(sov->list_mode == LM_NONE); > - sov->list_mode = LM_STARTED; > - sov->head = true; > + /* We don't support visits without a GenericList, yet */ without a list Do we plan to support them? If not, scratch "yet". > + assert(list); > + /* List handling is only needed if there are at least two elements */ > + if (*list && (*list)->next) { > + sov->list_mode = LM_STARTED; > + } > } > > -static GenericList *next_list(Visitor *v, GenericList **list, size_t size) > +static GenericList *next_list(Visitor *v, GenericList *tail, size_t size) > { > StringOutputVisitor *sov = to_sov(v); > - GenericList *ret = NULL; > - if (*list) { > - if (sov->head) { > - ret = *list; > - } else { > - ret = (*list)->next; > - } > + GenericList *ret = tail->next; > > - if (sov->head) { > - if (ret && ret->next == NULL) { > - sov->list_mode = LM_NONE; > - } > - sov->head = false; > - } else { > - if (ret && ret->next == NULL) { > - sov->list_mode = LM_END; > - } > - } > + if (ret && !ret->next) { > + sov->list_mode = LM_END; > } > - > return ret; > } > > @@ -311,8 +300,6 @@ static void end_list(Visitor *v) > sov->list_mode == LM_NONE || > sov->list_mode == LM_IN_PROGRESS); > sov->list_mode = LM_NONE; > - sov->head = true; > - > } > > char *string_output_get_string(StringOutputVisitor *sov) > diff --git a/docs/qapi-code-gen.txt b/docs/qapi-code-gen.txt > index 3b2422f..99080db 100644 > --- a/docs/qapi-code-gen.txt > +++ b/docs/qapi-code-gen.txt > @@ -912,18 +912,19 @@ Example: > void visit_type_UserDefOneList(Visitor *v, const char *name, UserDefOneList **obj, Error **errp) > { > Error *err = NULL; > - GenericList *i, **prev; > + UserDefOneList *tail; > + size_t size = sizeof(**obj); > > - visit_start_list(v, name, &err); > + visit_start_list(v, name, (GenericList **)obj, size, &err); > if (err) { > goto out; > } > - > - for (prev = (GenericList **)obj; > - !err && (i = visit_next_list(v, prev, sizeof(**obj))) != NULL; > - prev = &i) { > - UserDefOneList *native_i = (UserDefOneList *)i; > - visit_type_UserDefOne(v, NULL, &native_i->value, &err); > + for (tail = *obj; tail; > + tail = (UserDefOneList *)visit_next_list(v, (GenericList *)tail, size)) { > + visit_type_UserDefOne(v, NULL, &tail->value, &err); > + if (err) { > + break; > + } > } > > visit_end_list(v);
Markus Armbruster <armbru@redhat.com> writes: [...] >> diff --git a/qapi/string-input-visitor.c b/qapi/string-input-visitor.c >> index 797973a..77dd1a7 100644 >> --- a/qapi/string-input-visitor.c >> +++ b/qapi/string-input-visitor.c >> @@ -25,8 +25,6 @@ struct StringInputVisitor >> { >> Visitor visitor; >> >> - bool head; >> - >> GList *ranges; >> GList *cur_range; >> int64_t cur; >> @@ -125,11 +123,21 @@ error: >> } >> >> static void >> -start_list(Visitor *v, const char *name, Error **errp) >> +start_list(Visitor *v, const char *name, GenericList **list, size_t size, >> + Error **errp) >> { >> StringInputVisitor *siv = to_siv(v); >> + Error *err = NULL; >> >> - parse_str(siv, errp); >> + /* We don't support visits without a GenericList, yet */ > > without a list > > Do we plan to support them? If not, scratch "yet". > >> + assert(list); >> + >> + parse_str(siv, &err); >> + if (err) { >> + *list = NULL; >> + error_propagate(errp, err); >> + return; >> + } parse_str() never sets an error, and therefore your new error check is dead. Just as well, because it would be wrong. parse_str() parses a complete string into a non-empty list of uint64_t ranges. On success, it sets siv->ranges to this list. On error, it sets it to null. It could also set an error then, but it doesn't. If it did, then what would start_list() do with it? Reporting it would be wrong, because the list members need not be integers. If they aren't, the speculative parse_str()'s failure will be ignored. If they are, parse_type_int64() will call parse_str() again, then use siv->ranges. If the first parse_str() succeeds, the second will do nothing, and we'll use the first one's siv->ranges. Works. If the first parse_str() fails, the second will fail as well, because its input is the same. We'll use the second one's failure. Works. When used outside list context, parse_type_int64() will call parse_str() for the first time, and use its result. Works. Note that opts-visitor does it differently: opts_start_list() doesn't parse numbers, opts_type_int64() and opts_type_uint64() do. Further note the latent bug in parse_type_int64(): we first call parse_str(siv, errp), and goto error if it fails, where we promptly error_setg(errp, ...). If parse_str() set an error, the error_setg() would fail error_setv()'s assertion. Please drop parse_str()'s unused errp parameter, and add a comment to start_list() explaining the speculative call to parse_str() there. Alternatively, change the string visitor to work like the opts visitor. >> >> siv->cur_range = g_list_first(siv->ranges); >> if (siv->cur_range) { [...]
Markus Armbruster <armbru@redhat.com> writes: > Markus Armbruster <armbru@redhat.com> writes: > > [...] >>> diff --git a/qapi/string-input-visitor.c b/qapi/string-input-visitor.c >>> index 797973a..77dd1a7 100644 >>> --- a/qapi/string-input-visitor.c >>> +++ b/qapi/string-input-visitor.c >>> @@ -25,8 +25,6 @@ struct StringInputVisitor >>> { >>> Visitor visitor; >>> >>> - bool head; >>> - >>> GList *ranges; >>> GList *cur_range; >>> int64_t cur; >>> @@ -125,11 +123,21 @@ error: >>> } >>> >>> static void >>> -start_list(Visitor *v, const char *name, Error **errp) >>> +start_list(Visitor *v, const char *name, GenericList **list, size_t size, >>> + Error **errp) >>> { >>> StringInputVisitor *siv = to_siv(v); >>> + Error *err = NULL; >>> >>> - parse_str(siv, errp); >>> + /* We don't support visits without a GenericList, yet */ >> >> without a list >> >> Do we plan to support them? If not, scratch "yet". >> >>> + assert(list); >>> + >>> + parse_str(siv, &err); >>> + if (err) { >>> + *list = NULL; >>> + error_propagate(errp, err); >>> + return; >>> + } > > parse_str() never sets an error, and therefore your new error check is > dead. Just as well, because it would be wrong. > > parse_str() parses a complete string into a non-empty list of uint64_t > ranges. On success, it sets siv->ranges to this list. On error, it > sets it to null. It could also set an error then, but it doesn't. > > If it did, then what would start_list() do with it? Reporting it would > be wrong, because the list members need not be integers. > > If they aren't, the speculative parse_str()'s failure will be ignored. > > If they are, parse_type_int64() will call parse_str() again, then use > siv->ranges. > > If the first parse_str() succeeds, the second will do nothing, and we'll > use the first one's siv->ranges. Works. > > If the first parse_str() fails, the second will fail as well, because > its input is the same. We'll use the second one's failure. Works. No, it doesn't: failure gets interpreted as empty list. I'll post my test case separately. > When used outside list context, parse_type_int64() will call parse_str() > for the first time, and use its result. Works. > > Note that opts-visitor does it differently: opts_start_list() doesn't > parse numbers, opts_type_int64() and opts_type_uint64() do. > > Further note the latent bug in parse_type_int64(): we first call > parse_str(siv, errp), and goto error if it fails, where we promptly > error_setg(errp, ...). If parse_str() set an error, the error_setg() > would fail error_setv()'s assertion. > > Please drop parse_str()'s unused errp parameter, and add a comment to > start_list() explaining the speculative call to parse_str() there. Insufficient, doesn't fix the bug. After parse_str(), we need to be able to distinguish empty list from error. Moving the error_set() into parse_str() could work. Returning succes/failure and dropping the errp parameter could also work. > Alternatively, change the string visitor to work like the opts visitor. > >>> >>> siv->cur_range = g_list_first(siv->ranges); >>> if (siv->cur_range) { > [...]
On 04/22/2016 05:35 AM, Markus Armbruster wrote: >>>> >>>> static void >>>> -start_list(Visitor *v, const char *name, Error **errp) >>>> +start_list(Visitor *v, const char *name, GenericList **list, size_t size, >>>> + >>>> + parse_str(siv, &err); >>>> + if (err) { >>>> + *list = NULL; >>>> + error_propagate(errp, err); >>>> + return; >>>> + } >> >> parse_str() never sets an error, and therefore your new error check is >> dead. Just as well, because it would be wrong. >> >> parse_str() parses a complete string into a non-empty list of uint64_t >> ranges. On success, it sets siv->ranges to this list. On error, it >> sets it to null. It could also set an error then, but it doesn't. >> >> If it did, then what would start_list() do with it? Reporting it would >> be wrong, because the list members need not be integers. parse_str() is only ever called for start_list and parse_type_int64 - so the real question is do we ever support the string input visitor on anything other than an integral list. Per the comments I'm adding earlier in the series: * The string input visitor does not implement support for visiting * QAPI structs, alternates, null, or arbitrary QTypes. so it sounds like the only lists it supports ARE integer lists. >> >> If they aren't, the speculative parse_str()'s failure will be ignored. >> >> If they are, parse_type_int64() will call parse_str() again, then use >> siv->ranges. >> >> If the first parse_str() succeeds, the second will do nothing, and we'll >> use the first one's siv->ranges. Works. >> >> If the first parse_str() fails, the second will fail as well, because >> its input is the same. We'll use the second one's failure. Works. > > No, it doesn't: failure gets interpreted as empty list. I'll post my > test case separately. > >> When used outside list context, parse_type_int64() will call parse_str() >> for the first time, and use its result. Works. >> >> Note that opts-visitor does it differently: opts_start_list() doesn't >> parse numbers, opts_type_int64() and opts_type_uint64() do. I like the approach used in opts-visitor (start_list should only check if a list is present, but save the parsing for when the items are actually consumed off the list). But opts-visitor also handles structs, unlike the string visitor, which forces the separation (at start_list, we don't know what the list element will be, unlike the string visitor where we know the list element is integral). >> >> Further note the latent bug in parse_type_int64(): we first call >> parse_str(siv, errp), and goto error if it fails, where we promptly >> error_setg(errp, ...). If parse_str() set an error, the error_setg() >> would fail error_setv()'s assertion. >> >> Please drop parse_str()'s unused errp parameter, and add a comment to >> start_list() explaining the speculative call to parse_str() there. > > Insufficient, doesn't fix the bug. After parse_str(), we need to be > able to distinguish empty list from error. Moving the error_set() into > parse_str() could work. Returning succes/failure and dropping the errp > parameter could also work. I'm playing with these ideas, but will get the bug fixed (along with your testsuite addition) as a prerequisite to the list refactoring (to make sure that the refactored list still passes the fixed test). > >> Alternatively, change the string visitor to work like the opts visitor. Trickier, but may be my only option if the other approaches don't work. Thanks again for spotting yet another ugly corner case worth fixing (this series seems to have been a never-ending source of them...)
diff --git a/include/qapi/visitor.h b/include/qapi/visitor.h index e1213a3..a22a7ce 100644 --- a/include/qapi/visitor.h +++ b/include/qapi/visitor.h @@ -165,7 +165,7 @@ * if (err) { * goto outobj; * } - * visit_start_list(v, "list", &err); + * visit_start_list(v, "list", NULL, 0, &err); * if (err) { * goto outobj; * } @@ -268,40 +268,43 @@ void visit_end_struct(Visitor *v); * @name expresses the relationship of this list to its parent * container; see the general description of @name above. * + * @list must be non-NULL for a real walk, in which case @size + * determines how much memory an input visitor will allocate into + * *@list (at least sizeof(GenericList)). Some visitors also allow + * @list to be NULL for a virtual walk, in which case @size is + * ignored. + * * @errp must be NULL-initialized, and is set if an error is detected * (such as if a member @name is not present, or is present but not a - * list). + * list). On error, input visitors set *@obj to NULL. * * After visit_start_list() succeeds, the caller may visit its members - * one after the other. A real visit uses visit_next_list() for - * traversing the linked list, while a virtual visit uses other means. - * For each list element, call the appropriate visit_type_FOO() with - * name set to NULL and obj set to the address of the value member of - * the list element. Finally, visit_end_list() needs to be called to - * clean up, even if intermediate visits fail. See the examples - * above. + * one after the other. A real visit (where @obj is non-NULL) uses + * visit_next_list() for traversing the linked list, while a virtual + * visit (where @obj is NULL) uses other means. For each list + * element, call the appropriate visit_type_FOO() with name set to + * NULL and obj set to the address of the value member of the list + * element. Finally, visit_end_list() needs to be called to clean up, + * even if intermediate visits fail. See the examples above. */ -void visit_start_list(Visitor *v, const char *name, Error **errp); +void visit_start_list(Visitor *v, const char *name, GenericList **list, + size_t size, Error **errp); /* - * Iterate over a GenericList during a list visit. + * Iterate over a GenericList during a non-virtual list visit. * - * @size represents the size of a linked list node. + * @size represents the size of a linked list node (at least + * sizeof(GenericList)). * - * @list must not be NULL; on the first call, @list contains the - * address of the list head, and on subsequent calls *@list must be - * the previously returned value. Must be called in a loop until a + * @tail must not be NULL; on the first call, @tail is the value of + * *list after visit_start_list(), and on subsequent calls @tail must + * be the previously returned value. Must be called in a loop until a * NULL return or error occurs; for each non-NULL return, the caller * must then call the appropriate visit_type_*() for the element type * of the list, with that function's name parameter set to NULL and - * obj set to the address of (*@list)->value. - * - * FIXME: This interface is awkward; it requires all callbacks to - * track whether it is the first or a subsequent call. A better - * interface would pass the head of the list through - * visit_start_list(). + * obj set to the address of @tail->value. */ -GenericList *visit_next_list(Visitor *v, GenericList **list, size_t size); +GenericList *visit_next_list(Visitor *v, GenericList *tail, size_t size); /* * Complete a list visit started earlier. diff --git a/include/qapi/visitor-impl.h b/include/qapi/visitor-impl.h index d44fcd1..0471465 100644 --- a/include/qapi/visitor-impl.h +++ b/include/qapi/visitor-impl.h @@ -45,11 +45,12 @@ struct Visitor /* Must be set to visit structs. */ void (*end_struct)(Visitor *v); - /* Must be set. */ - void (*start_list)(Visitor *v, const char *name, Error **errp); + /* Must be set; document if @list may not be NULL. */ + void (*start_list)(Visitor *v, const char *name, GenericList **list, + size_t size, Error **errp); /* Must be set. */ - GenericList *(*next_list)(Visitor *v, GenericList **list, size_t size); + GenericList *(*next_list)(Visitor *v, GenericList *tail, size_t size); /* Must be set. */ void (*end_list)(Visitor *v); diff --git a/scripts/qapi-visit.py b/scripts/qapi-visit.py index bfe4a09..69f0133 100644 --- a/scripts/qapi-visit.py +++ b/scripts/qapi-visit.py @@ -117,20 +117,20 @@ def gen_visit_list(name, element_type): void visit_type_%(c_name)s(Visitor *v, const char *name, %(c_name)s **obj, Error **errp) { Error *err = NULL; - GenericList *i, **prev; + %(c_name)s *tail; + size_t size = sizeof(**obj); - visit_start_list(v, name, &err); + visit_start_list(v, name, (GenericList **)obj, size, &err); if (err) { goto out; } - - for (prev = (GenericList **)obj; - !err && (i = visit_next_list(v, prev, sizeof(**obj))) != NULL; - prev = &i) { - %(c_name)s *native_i = (%(c_name)s *)i; - visit_type_%(c_elt_type)s(v, NULL, &native_i->value, &err); + for (tail = *obj; tail; + tail = (%(c_name)s *)visit_next_list(v, (GenericList *)tail, size)) { + visit_type_%(c_elt_type)s(v, NULL, &tail->value, &err); + if (err) { + break; + } } - visit_end_list(v); out: error_propagate(errp, err); diff --git a/include/qapi/opts-visitor.h b/include/qapi/opts-visitor.h index 3fcd327..7c9a7e5 100644 --- a/include/qapi/opts-visitor.h +++ b/include/qapi/opts-visitor.h @@ -32,7 +32,7 @@ typedef struct OptsVisitor OptsVisitor; * * The Opts input visitor does not yet implement support for visiting * QAPI alternates, numbers (other than integers), null, or arbitrary - * QTypes. + * QTypes. It also requires non-NULL list to visit_start_list(). */ OptsVisitor *opts_visitor_new(const QemuOpts *opts); void opts_visitor_cleanup(OptsVisitor *nv); diff --git a/include/qapi/string-input-visitor.h b/include/qapi/string-input-visitor.h index 1a34c52..d26a845 100644 --- a/include/qapi/string-input-visitor.h +++ b/include/qapi/string-input-visitor.h @@ -19,7 +19,8 @@ typedef struct StringInputVisitor StringInputVisitor; /* * The string input visitor does not yet implement support for - * visiting QAPI structs, alternates, null, or arbitrary QTypes. + * visiting QAPI structs, alternates, null, or arbitrary QTypes. It + * also requires non-NULL list to visit_start_list(). */ StringInputVisitor *string_input_visitor_new(const char *str); void string_input_visitor_cleanup(StringInputVisitor *v); diff --git a/include/qapi/string-output-visitor.h b/include/qapi/string-output-visitor.h index 2564833..0a9354c 100644 --- a/include/qapi/string-output-visitor.h +++ b/include/qapi/string-output-visitor.h @@ -19,7 +19,8 @@ typedef struct StringOutputVisitor StringOutputVisitor; /* * The string output visitor does not yet implement support for - * visiting QAPI structs, alternates, null, or arbitrary QTypes. + * visiting QAPI structs, alternates, null, or arbitrary QTypes. It + * also requires non-NULL list to visit_start_list(). */ StringOutputVisitor *string_output_visitor_new(bool human); void string_output_visitor_cleanup(StringOutputVisitor *v); diff --git a/qapi/qapi-visit-core.c b/qapi/qapi-visit-core.c index 76ea690..622b315 100644 --- a/qapi/qapi-visit-core.c +++ b/qapi/qapi-visit-core.c @@ -42,15 +42,17 @@ void visit_end_struct(Visitor *v) v->end_struct(v); } -void visit_start_list(Visitor *v, const char *name, Error **errp) +void visit_start_list(Visitor *v, const char *name, GenericList **list, + size_t size, Error **errp) { - v->start_list(v, name, errp); + assert(!list || size >= sizeof(GenericList)); + v->start_list(v, name, list, size, errp); } -GenericList *visit_next_list(Visitor *v, GenericList **list, size_t size) +GenericList *visit_next_list(Visitor *v, GenericList *tail, size_t size) { - assert(list && size >= sizeof(GenericList)); - return v->next_list(v, list, size); + assert(tail && size >= sizeof(GenericList)); + return v->next_list(v, tail, size); } void visit_end_list(Visitor *v) diff --git a/hw/ppc/spapr_drc.c b/hw/ppc/spapr_drc.c index 5395c02..dd3c502 100644 --- a/hw/ppc/spapr_drc.c +++ b/hw/ppc/spapr_drc.c @@ -309,7 +309,7 @@ static void prop_get_fdt(Object *obj, Visitor *v, const char *name, int i; prop = fdt_get_property_by_offset(fdt, fdt_offset, &prop_len); name = fdt_string(fdt, fdt32_to_cpu(prop->nameoff)); - visit_start_list(v, name, &err); + visit_start_list(v, name, NULL, 0, &err); if (err) { error_propagate(errp, err); return; diff --git a/qapi/opts-visitor.c b/qapi/opts-visitor.c index a08d5a7..6d572cc 100644 --- a/qapi/opts-visitor.c +++ b/qapi/opts-visitor.c @@ -23,9 +23,8 @@ enum ListMode { LM_NONE, /* not traversing a list of repeated options */ - LM_STARTED, /* opts_start_list() succeeded */ - LM_IN_PROGRESS, /* opts_next_list() has been called. + LM_IN_PROGRESS, /* opts_next_list() ready to be called. * * Generating the next list link will consume the most * recently parsed QemuOpt instance of the repeated @@ -214,35 +213,33 @@ lookup_distinct(const OptsVisitor *ov, const char *name, Error **errp) static void -opts_start_list(Visitor *v, const char *name, Error **errp) +opts_start_list(Visitor *v, const char *name, GenericList **list, size_t size, + Error **errp) { OptsVisitor *ov = to_ov(v); /* we can't traverse a list in a list */ assert(ov->list_mode == LM_NONE); + /* we don't support visits without GenericList, yet */ + assert(list); ov->repeated_opts = lookup_distinct(ov, name, errp); - if (ov->repeated_opts != NULL) { - ov->list_mode = LM_STARTED; + if (ov->repeated_opts) { + ov->list_mode = LM_IN_PROGRESS; + *list = g_malloc0(size); + } else { + *list = NULL; } } static GenericList * -opts_next_list(Visitor *v, GenericList **list, size_t size) +opts_next_list(Visitor *v, GenericList *tail, size_t size) { OptsVisitor *ov = to_ov(v); - GenericList **link; switch (ov->list_mode) { - case LM_STARTED: - ov->list_mode = LM_IN_PROGRESS; - link = list; - break; - case LM_SIGNED_INTERVAL: case LM_UNSIGNED_INTERVAL: - link = &(*list)->next; - if (ov->list_mode == LM_SIGNED_INTERVAL) { if (ov->range_next.s < ov->range_limit.s) { ++ov->range_next.s; @@ -263,7 +260,6 @@ opts_next_list(Visitor *v, GenericList **list, size_t size) g_hash_table_remove(ov->unprocessed_opts, opt->name); return NULL; } - link = &(*list)->next; break; } @@ -271,8 +267,8 @@ opts_next_list(Visitor *v, GenericList **list, size_t size) abort(); } - *link = g_malloc0(size); - return *link; + tail->next = g_malloc0(size); + return tail->next; } @@ -281,8 +277,7 @@ opts_end_list(Visitor *v) { OptsVisitor *ov = to_ov(v); - assert(ov->list_mode == LM_STARTED || - ov->list_mode == LM_IN_PROGRESS || + assert(ov->list_mode == LM_IN_PROGRESS || ov->list_mode == LM_SIGNED_INTERVAL || ov->list_mode == LM_UNSIGNED_INTERVAL); ov->repeated_opts = NULL; diff --git a/qapi/qapi-dealloc-visitor.c b/qapi/qapi-dealloc-visitor.c index 9005bad..cd68b55 100644 --- a/qapi/qapi-dealloc-visitor.c +++ b/qapi/qapi-dealloc-visitor.c @@ -22,7 +22,6 @@ typedef struct StackEntry { void *value; - bool is_list_head; QTAILQ_ENTRY(StackEntry) node; } StackEntry; @@ -43,10 +42,6 @@ static void qapi_dealloc_push(QapiDeallocVisitor *qov, void *value) e->value = value; - /* see if we're just pushing a list head tracker */ - if (value == NULL) { - e->is_list_head = true; - } QTAILQ_INSERT_HEAD(&qov->stack, e, node); } @@ -93,38 +88,22 @@ static void qapi_dealloc_end_alternate(Visitor *v) } } -static void qapi_dealloc_start_list(Visitor *v, const char *name, Error **errp) +static void qapi_dealloc_start_list(Visitor *v, const char *name, + GenericList **list, size_t size, + Error **errp) { - QapiDeallocVisitor *qov = to_qov(v); - qapi_dealloc_push(qov, NULL); } -static GenericList *qapi_dealloc_next_list(Visitor *v, GenericList **listp, +static GenericList *qapi_dealloc_next_list(Visitor *v, GenericList *tail, size_t size) { - GenericList *list = *listp; - QapiDeallocVisitor *qov = to_qov(v); - StackEntry *e = QTAILQ_FIRST(&qov->stack); - - if (e && e->is_list_head) { - e->is_list_head = false; - return list; - } - - if (list) { - list = list->next; - g_free(*listp); - return list; - } - - return NULL; + GenericList *next = tail->next; + g_free(tail); + return next; } static void qapi_dealloc_end_list(Visitor *v) { - QapiDeallocVisitor *qov = to_qov(v); - void *obj = qapi_dealloc_pop(qov); - assert(obj == NULL); /* should've been list head tracker with no payload */ } static void qapi_dealloc_type_str(Visitor *v, const char *name, char **obj, diff --git a/qapi/qmp-input-visitor.c b/qapi/qmp-input-visitor.c index 16f2f5a..5360744 100644 --- a/qapi/qmp-input-visitor.c +++ b/qapi/qmp-input-visitor.c @@ -29,8 +29,6 @@ typedef struct StackObject /* If obj is list: tail of list still needing visits */ const QListEntry *entry; - /* If obj is list: true if head is not visited yet */ - bool first; GHashTable *h; /* If obj is dict: remaining keys needing visits */ } StackObject; @@ -87,7 +85,6 @@ static QObject *qmp_input_get_object(QmpInputVisitor *qiv, assert(!name); if (tos->entry) { - assert(!tos->first); qobj = qlist_entry_obj(tos->entry); if (consume) { tos->entry = qlist_next(tos->entry); @@ -117,7 +114,6 @@ static void qmp_input_push(QmpInputVisitor *qiv, QObject *obj, tos->obj = obj; tos->entry = entry; - tos->first = true; tos->h = NULL; if (qiv->strict && qobject_type(obj) == QTYPE_QDICT) { @@ -194,13 +190,17 @@ static void qmp_input_start_struct(Visitor *v, const char *name, void **obj, } -static void qmp_input_start_list(Visitor *v, const char *name, Error **errp) +static void qmp_input_start_list(Visitor *v, const char *name, + GenericList **list, size_t size, Error **errp) { QmpInputVisitor *qiv = to_qiv(v); QObject *qobj = qmp_input_get_object(qiv, name, true); const QListEntry *entry; if (!qobj || qobject_type(qobj) != QTYPE_QLIST) { + if (list) { + *list = NULL; + } error_setg(errp, QERR_INVALID_PARAMETER_TYPE, name ? name : "null", "list"); return; @@ -208,28 +208,26 @@ static void qmp_input_start_list(Visitor *v, const char *name, Error **errp) entry = qlist_first(qobject_to_qlist(qobj)); qmp_input_push(qiv, qobj, entry, errp); + if (list) { + if (entry) { + *list = g_malloc0(size); + } else { + *list = NULL; + } + } } -static GenericList *qmp_input_next_list(Visitor *v, GenericList **list, +static GenericList *qmp_input_next_list(Visitor *v, GenericList *tail, size_t size) { QmpInputVisitor *qiv = to_qiv(v); - GenericList *entry; StackObject *so = &qiv->stack[qiv->nb_stack - 1]; if (!so->entry) { return NULL; } - - entry = g_malloc0(size); - if (so->first) { - *list = entry; - so->first = false; - } else { - (*list)->next = entry; - } - - return entry; + tail->next = g_malloc0(size); + return tail->next; } diff --git a/qapi/qmp-output-visitor.c b/qapi/qmp-output-visitor.c index ecb2005..40657be 100644 --- a/qapi/qmp-output-visitor.c +++ b/qapi/qmp-output-visitor.c @@ -22,7 +22,6 @@ typedef struct QStackEntry { QObject *value; - bool is_list_head; QTAILQ_ENTRY(QStackEntry) node; } QStackEntry; @@ -52,9 +51,6 @@ static void qmp_output_push_obj(QmpOutputVisitor *qov, QObject *value) assert(qov->root); assert(value); e->value = value; - if (qobject_type(e->value) == QTYPE_QLIST) { - e->is_list_head = true; - } QTAILQ_INSERT_HEAD(&qov->stack, e, node); } @@ -120,7 +116,9 @@ static void qmp_output_end_struct(Visitor *v) assert(qobject_type(value) == QTYPE_QDICT); } -static void qmp_output_start_list(Visitor *v, const char *name, Error **errp) +static void qmp_output_start_list(Visitor *v, const char *name, + GenericList **listp, size_t size, + Error **errp) { QmpOutputVisitor *qov = to_qov(v); QList *list = qlist_new(); @@ -129,20 +127,10 @@ static void qmp_output_start_list(Visitor *v, const char *name, Error **errp) qmp_output_push(qov, list); } -static GenericList *qmp_output_next_list(Visitor *v, GenericList **listp, +static GenericList *qmp_output_next_list(Visitor *v, GenericList *tail, size_t size) { - GenericList *list = *listp; - QmpOutputVisitor *qov = to_qov(v); - QStackEntry *e = QTAILQ_FIRST(&qov->stack); - - assert(e); - if (e->is_list_head) { - e->is_list_head = false; - return list; - } - - return list ? list->next : NULL; + return tail->next; } static void qmp_output_end_list(Visitor *v) diff --git a/qapi/string-input-visitor.c b/qapi/string-input-visitor.c index 797973a..77dd1a7 100644 --- a/qapi/string-input-visitor.c +++ b/qapi/string-input-visitor.c @@ -25,8 +25,6 @@ struct StringInputVisitor { Visitor visitor; - bool head; - GList *ranges; GList *cur_range; int64_t cur; @@ -125,11 +123,21 @@ error: } static void -start_list(Visitor *v, const char *name, Error **errp) +start_list(Visitor *v, const char *name, GenericList **list, size_t size, + Error **errp) { StringInputVisitor *siv = to_siv(v); + Error *err = NULL; - parse_str(siv, errp); + /* We don't support visits without a GenericList, yet */ + assert(list); + + parse_str(siv, &err); + if (err) { + *list = NULL; + error_propagate(errp, err); + return; + } siv->cur_range = g_list_first(siv->ranges); if (siv->cur_range) { @@ -137,13 +145,15 @@ start_list(Visitor *v, const char *name, Error **errp) if (r) { siv->cur = r->begin; } + *list = g_malloc0(size); + } else { + *list = NULL; } } -static GenericList *next_list(Visitor *v, GenericList **list, size_t size) +static GenericList *next_list(Visitor *v, GenericList *tail, size_t size) { StringInputVisitor *siv = to_siv(v); - GenericList **link; Range *r; if (!siv->ranges || !siv->cur_range) { @@ -167,21 +177,12 @@ static GenericList *next_list(Visitor *v, GenericList **list, size_t size) siv->cur = r->begin; } - if (siv->head) { - link = list; - siv->head = false; - } else { - link = &(*list)->next; - } - - *link = g_malloc0(size); - return *link; + tail->next = g_malloc0(size); + return tail->next; } static void end_list(Visitor *v) { - StringInputVisitor *siv = to_siv(v); - siv->head = true; } static void parse_type_int64(Visitor *v, const char *name, int64_t *obj, @@ -362,6 +363,5 @@ StringInputVisitor *string_input_visitor_new(const char *str) v->visitor.optional = parse_optional; v->string = str; - v->head = true; return v; } diff --git a/qapi/string-output-visitor.c b/qapi/string-output-visitor.c index 0d44d7e..e27e2df 100644 --- a/qapi/string-output-visitor.c +++ b/qapi/string-output-visitor.c @@ -20,7 +20,7 @@ enum ListMode { LM_NONE, /* not traversing a list of repeated options */ - LM_STARTED, /* start_list() succeeded */ + LM_STARTED, /* start_list() succeeded with multiple elements */ LM_IN_PROGRESS, /* next_list() has been called. * @@ -48,7 +48,7 @@ enum ListMode { LM_UNSIGNED_INTERVAL,/* Same as above, only for an unsigned interval. */ - LM_END + LM_END, /* next_list() called, about to see last element. */ }; typedef enum ListMode ListMode; @@ -58,7 +58,6 @@ struct StringOutputVisitor Visitor visitor; bool human; GString *string; - bool head; ListMode list_mode; union { int64_t s; @@ -266,39 +265,29 @@ static void print_type_number(Visitor *v, const char *name, double *obj, } static void -start_list(Visitor *v, const char *name, Error **errp) +start_list(Visitor *v, const char *name, GenericList **list, size_t size, + Error **errp) { StringOutputVisitor *sov = to_sov(v); /* we can't traverse a list in a list */ assert(sov->list_mode == LM_NONE); - sov->list_mode = LM_STARTED; - sov->head = true; + /* We don't support visits without a GenericList, yet */ + assert(list); + /* List handling is only needed if there are at least two elements */ + if (*list && (*list)->next) { + sov->list_mode = LM_STARTED; + } } -static GenericList *next_list(Visitor *v, GenericList **list, size_t size) +static GenericList *next_list(Visitor *v, GenericList *tail, size_t size) { StringOutputVisitor *sov = to_sov(v); - GenericList *ret = NULL; - if (*list) { - if (sov->head) { - ret = *list; - } else { - ret = (*list)->next; - } + GenericList *ret = tail->next; - if (sov->head) { - if (ret && ret->next == NULL) { - sov->list_mode = LM_NONE; - } - sov->head = false; - } else { - if (ret && ret->next == NULL) { - sov->list_mode = LM_END; - } - } + if (ret && !ret->next) { + sov->list_mode = LM_END; } - return ret; } @@ -311,8 +300,6 @@ static void end_list(Visitor *v) sov->list_mode == LM_NONE || sov->list_mode == LM_IN_PROGRESS); sov->list_mode = LM_NONE; - sov->head = true; - } char *string_output_get_string(StringOutputVisitor *sov) diff --git a/docs/qapi-code-gen.txt b/docs/qapi-code-gen.txt index 3b2422f..99080db 100644 --- a/docs/qapi-code-gen.txt +++ b/docs/qapi-code-gen.txt @@ -912,18 +912,19 @@ Example: void visit_type_UserDefOneList(Visitor *v, const char *name, UserDefOneList **obj, Error **errp) { Error *err = NULL; - GenericList *i, **prev; + UserDefOneList *tail; + size_t size = sizeof(**obj); - visit_start_list(v, name, &err); + visit_start_list(v, name, (GenericList **)obj, size, &err); if (err) { goto out; } - - for (prev = (GenericList **)obj; - !err && (i = visit_next_list(v, prev, sizeof(**obj))) != NULL; - prev = &i) { - UserDefOneList *native_i = (UserDefOneList *)i; - visit_type_UserDefOne(v, NULL, &native_i->value, &err); + for (tail = *obj; tail; + tail = (UserDefOneList *)visit_next_list(v, (GenericList *)tail, size)) { + visit_type_UserDefOne(v, NULL, &tail->value, &err); + if (err) { + break; + } } visit_end_list(v);
We have two uses of list visits in the entire code base: one in spapr_drc (which completely avoids visit_next_list(), feeding in integers from a different source than uint8List), and one in qapi-visit.py (that is, all other list visitors are generated in qapi-visit.c, and share the same paradigm based on a qapi FooList type). What's more, the semantics of the list visit are somewhat baroque, with the following pseudocode when FooList is used: start() for (prev = head; cur = next(prev); prev = &cur) { visit(&cur->value) } Note that these semantics (advance before visit) requires that the first call to next() return the list head, while all other calls return the next element of the list; that is, every visitor implementation is required to track extra state to decide whether to return the input as-is, or to advance. It also requires an argument of 'GenericList **' to next(), solely because the first iteration might need to modify the caller's GenericList head, so that all other calls have to do a layer of dereferencing. We can greatly simplify things by hoisting the special case into the start() routine, and flipping the order in the loop to visit before advance: start(head) for (tail = *head; tail; tail = next(tail)) { visit(&tail->value) } With the simpler semantics, visitors have less state to track, the argument to next() is reduced to 'GenericList *', and it also becomes obvious whether an input visitor is allocating a FooList during visit_start_list() (rather than the old way of not knowing if an allocation happened until the first visit_next_list()). The signature of visit_start_list() is chosen to match visit_start_struct(), with the new parameters after 'name'. The spapr_drc case is a virtual visit, done by passing NULL for list, similarly to how NULL is passed to visit_start_struct() when a qapi type is not used in those visits. It was easy to provide these semantics for qmp-output and dealloc visitors, and a bit harder for qmp-input (several prerequisite patches refactored things to make this patch straightforward). But it turned out that the string and opts visitors munge enough other state during visit_next_list() to make it easier to just document and require a GenericList visit for now; an assertion will remind us to adjust things if we need the semantics in the future. Signed-off-by: Eric Blake <eblake@redhat.com> --- v14: no change v13: documentation wording tweaks v12: rebase to earlier changes, drop R-b, improve documentation, split out qmp-input cleanups into prereq patches [no v10, v11] v9: no change v8: consistent parameter order, fix qmp_input_get_next_type() to not skip list entries v7: new patch --- include/qapi/visitor.h | 47 +++++++++++++++++++----------------- include/qapi/visitor-impl.h | 7 +++--- scripts/qapi-visit.py | 18 +++++++------- include/qapi/opts-visitor.h | 2 +- include/qapi/string-input-visitor.h | 3 ++- include/qapi/string-output-visitor.h | 3 ++- qapi/qapi-visit-core.c | 12 +++++---- hw/ppc/spapr_drc.c | 2 +- qapi/opts-visitor.c | 33 +++++++++++-------------- qapi/qapi-dealloc-visitor.c | 35 ++++++--------------------- qapi/qmp-input-visitor.c | 32 ++++++++++++------------ qapi/qmp-output-visitor.c | 22 ++++------------- qapi/string-input-visitor.c | 36 +++++++++++++-------------- qapi/string-output-visitor.c | 41 +++++++++++-------------------- docs/qapi-code-gen.txt | 17 +++++++------ 15 files changed, 133 insertions(+), 177 deletions(-)