[Qemu-devel] [PATCH v6 15/16] qapi: Share gen_err_check()

[Eric Blake <eblake@redhat.com>]

qapi-commands had a nice helper gen_err_check(), but did not
use it everywhere. In fact, using it in more places makes it
easier to reduce the lines of code used in appending an error
check in generated code (previously required a multi-line
mcgen(), which didn't add any use of parameterization), which
in turn makes it easier to write the next patch which will
consolidate another common pattern among the generators.

The diffstat of this patch doesn't quite show as big a
reduction in lines as I had hoped, but that is in part due to
the duplication of some FIXME comments.

Signed-off-by: Eric Blake <eblake@redhat.com>

---
v6: new, split off of 10/46, add label parameter, and catch more
instances that could use it
---
 scripts/qapi-commands.py | 29 +++++++-------------
 scripts/qapi-event.py    | 16 +++++------
 scripts/qapi-visit.py    | 69 ++++++++++++++++++++++++------------------------
 scripts/qapi.py          | 12 +++++++++
 4 files changed, 62 insertions(+), 64 deletions(-)

diff --git a/scripts/qapi-commands.py b/scripts/qapi-commands.py
index 1d3c0d5..713aa0b 100644
--- a/scripts/qapi-commands.py
+++ b/scripts/qapi-commands.py
@@ -25,17 +25,6 @@ def gen_command_decl(name, arg_type, ret_type):
                  params=gen_params(arg_type, 'Error **errp'))


-def gen_err_check(err):
-    if not err:
-        return ''
-    return mcgen('''
-    if (%(err)s) {
-        goto out;
-    }
-''',
-                 err=err)
-
-
 def gen_call(name, arg_type, ret_type):
     ret = ''

@@ -56,7 +45,7 @@ def gen_call(name, arg_type, ret_type):
 ''',
                 c_name=c_name(name), args=argstr, lhs=lhs)
     if ret_type:
-        ret += gen_err_check('err')
+        ret += gen_err_check()
         ret += mcgen('''

     qmp_marshal_output_%(c_name)s(retval, ret, &err);
@@ -133,7 +122,7 @@ def gen_marshal_input_visit(arg_type, dealloc=False):
 ''',
                          c_name=c_name(memb.name), name=memb.name,
                          errp=errparg)
-            ret += gen_err_check(errarg)
+            ret += gen_err_check(err=errarg)
             ret += mcgen('''
     if (has_%(c_name)s) {
 ''',
@@ -144,7 +133,7 @@ def gen_marshal_input_visit(arg_type, dealloc=False):
 ''',
                      c_name=c_name(memb.name), name=memb.name,
                      c_type=memb.type.c_name(), errp=errparg)
-        ret += gen_err_check(errarg)
+        ret += gen_err_check(err=errarg)
         if memb.optional:
             pop_indent()
             ret += mcgen('''
@@ -159,7 +148,7 @@ def gen_marshal_input_visit(arg_type, dealloc=False):


 def gen_marshal_output(ret_type):
-    return mcgen('''
+    ret = mcgen('''

 static void qmp_marshal_output_%(c_name)s(%(c_type)s ret_in, QObject **ret_out, Error **errp)
 {
@@ -170,9 +159,10 @@ static void qmp_marshal_output_%(c_name)s(%(c_type)s ret_in, QObject **ret_out,

     v = qmp_output_get_visitor(qov);
     visit_type_%(c_name)s(v, &ret_in, "unused", &err);
-    if (err) {
-        goto out;
-    }
+''',
+                c_type=ret_type.c_type(), c_name=ret_type.c_name())
+    ret += gen_err_check()
+    ret += mcgen('''
     *ret_out = qmp_output_get_qobject(qov);

  out:
@@ -184,7 +174,8 @@ static void qmp_marshal_output_%(c_name)s(%(c_type)s ret_in, QObject **ret_out,
     qapi_dealloc_visitor_cleanup(qdv);
 }
 ''',
-                 c_type=ret_type.c_type(), c_name=ret_type.c_name())
+                 c_name=ret_type.c_name())
+    return ret


 def gen_marshal_proto(name):
diff --git a/scripts/qapi-event.py b/scripts/qapi-event.py
index b43bbc2..bbc6169 100644
--- a/scripts/qapi-event.py
+++ b/scripts/qapi-event.py
@@ -68,12 +68,10 @@ def gen_event_send(name, arg_type):

     /* Fake visit, as if all members are under a structure */
     visit_start_struct(v, NULL, "", "%(name)s", 0, &err);
-    if (err) {
-        goto out;
-    }
-
 ''',
                      name=name)
+        ret += gen_err_check()
+        ret += '\n'

         for memb in arg_type.members:
             if memb.optional:
@@ -91,14 +89,12 @@ def gen_event_send(name, arg_type):

             ret += mcgen('''
     visit_type_%(c_type)s(v, %(cast)s&%(c_name)s, "%(name)s", &err);
-    if (err) {
-        goto out;
-    }
 ''',
                          cast=cast,
                          c_name=c_name(memb.name),
                          c_type=memb.type.c_name(),
                          name=memb.name)
+            ret += gen_err_check()

             if memb.optional:
                 pop_indent()
@@ -109,9 +105,9 @@ def gen_event_send(name, arg_type):
         ret += mcgen('''

     visit_end_struct(v, &err);
-    if (err) {
-        goto out;
-    }
+''')
+        ret += gen_err_check()
+        ret += mcgen('''

     obj = qmp_output_get_qobject(qov);
     g_assert(obj != NULL);
diff --git a/scripts/qapi-visit.py b/scripts/qapi-visit.py
index 7ce8616..fec07ad 100644
--- a/scripts/qapi-visit.py
+++ b/scripts/qapi-visit.py
@@ -81,11 +81,9 @@ static void visit_type_%(c_name)s_fields(Visitor *v, %(c_name)s **obj, Error **e
     if base:
         ret += mcgen('''
     visit_type_implicit_%(c_type)s(v, &(*obj)->%(c_name)s, &err);
-    if (err) {
-        goto out;
-    }
 ''',
                      c_type=base.c_name(), c_name=c_name('base'))
+        ret += gen_err_check()

     for memb in members:
         if memb.optional:
@@ -107,11 +105,7 @@ static void visit_type_%(c_name)s_fields(Visitor *v, %(c_name)s **obj, Error **e
             ret += mcgen('''
     }
 ''')
-        ret += mcgen('''
-    if (err) {
-        goto out;
-    }
-''')
+        ret += gen_err_check()

     if re.search('^ *goto out;', ret, re.MULTILINE):
         ret += mcgen('''
@@ -154,7 +148,7 @@ void visit_type_%(c_name)s(Visitor *v, %(c_name)s **obj, const char *name, Error


 def gen_visit_list(name, element_type):
-    return mcgen('''
+    ret = mcgen('''

 void visit_type_%(c_name)s(Visitor *v, %(c_name)s **obj, const char *name, Error **errp)
 {
@@ -162,9 +156,10 @@ void visit_type_%(c_name)s(Visitor *v, %(c_name)s **obj, const char *name, Error
     GenericList *i, **prev;

     visit_start_list(v, name, &err);
-    if (err) {
-        goto out;
-    }
+''',
+                c_name=c_name(name), c_elt_type=element_type.c_name())
+    ret += gen_err_check()
+    ret += mcgen('''

     for (prev = (GenericList **)obj;
          !err && (i = visit_next_list(v, prev, &err)) != NULL;
@@ -181,6 +176,7 @@ void visit_type_%(c_name)s(Visitor *v, %(c_name)s **obj, const char *name, Error
 }
 ''',
                  c_name=c_name(name), c_elt_type=element_type.c_name())
+    return ret


 def gen_visit_enum(name):
@@ -202,16 +198,17 @@ void visit_type_%(c_name)s(Visitor *v, %(c_name)s **obj, const char *name, Error
     Error *err = NULL;

     visit_start_implicit_struct(v, (void**) obj, sizeof(%(c_name)s), &err);
-    if (err) {
-        goto out;
-    }
+''',
+                c_name=c_name(name))
+    ret += gen_err_check()
+    ret += mcgen('''
     visit_get_next_type(v, (int*) &(*obj)->kind, %(c_name)s_qtypes, name, &err);
-    if (err) {
-        goto out_obj;
-    }
+''',
+                 c_name=c_name(name))
+    ret += gen_err_check(label='out_obj')
+    ret += mcgen('''
     switch ((*obj)->kind) {
-''',
-                c_name=c_name(name))
+''')

     for var in variants.variants:
         ret += mcgen('''
@@ -259,23 +256,21 @@ void visit_type_%(c_name)s(Visitor *v, %(c_name)s **obj, const char *name, Error
     Error *err = NULL;

     visit_start_struct(v, (void **)obj, "%(name)s", name, sizeof(%(c_name)s), &err);
-    if (err) {
-        goto out;
-    }
+''',
+                 c_name=c_name(name), name=name)
+    ret += gen_err_check()
+    ret += mcgen('''
     if (!*obj) {
         goto out_obj;
     }
-''',
-                 c_name=c_name(name), name=name)
+''')

     if base:
         ret += mcgen('''
     visit_type_%(c_name)s_fields(v, obj, &err);
-    if (err) {
-        goto out_obj;
-    }
 ''',
                      c_name=c_name(name))
+        ret += gen_err_check(label='out_obj')

     tag_key = variants.tag_member.name
     if not variants.tag_name:
@@ -283,13 +278,6 @@ void visit_type_%(c_name)s(Visitor *v, %(c_name)s **obj, const char *name, Error
         tag_key = 'type'
     ret += mcgen('''
     visit_type_%(c_type)s(v, &(*obj)->%(c_name)s, "%(name)s", &err);
-    if (err) {
-        goto out_obj;
-    }
-    if (!visit_start_union(v, !!(*obj)->data, &err) || err) {
-        goto out_obj;
-    }
-    switch ((*obj)->%(c_name)s) {
 ''',
                  c_type=variants.tag_member.type.c_name(),
                  # TODO ugly special case for simple union
@@ -297,6 +285,17 @@ void visit_type_%(c_name)s(Visitor *v, %(c_name)s **obj, const char *name, Error
                  # it, then: c_name=c_name(variants.tag_member.name)
                  c_name=c_name(variants.tag_name or 'kind'),
                  name=tag_key)
+    ret += gen_err_check(label='out_obj')
+    ret += mcgen('''
+    if (!visit_start_union(v, !!(*obj)->data, &err) || err) {
+        goto out_obj;
+    }
+    switch ((*obj)->%(c_name)s) {
+''',
+                 # TODO ugly special case for simple union
+                 # Use same tag name in C as on the wire to get rid of
+                 # it, then: c_name=c_name(variants.tag_member.name)
+                 c_name=c_name(variants.tag_name or 'kind'))

     for var in variants.variants:
         # TODO ugly special case for simple union
diff --git a/scripts/qapi.py b/scripts/qapi.py
index 4825e62..0593b71 100644
--- a/scripts/qapi.py
+++ b/scripts/qapi.py
@@ -1536,6 +1536,18 @@ def gen_params(arg_type, extra):
         ret += sep + extra
     return ret

+
+def gen_err_check(err='err', label='out'):
+    if not err:
+        return ''
+    return mcgen('''
+    if (%(err)s) {
+        goto %(label)s;
+    }
+''',
+                 err=err, label=label)
+
+
 #
 # Common command line parsing
 #
-- 
2.4.3