Re: [Qemu-devel] [PATCH 2/4] string-input-visitor: Support alternate types

[Markus Armbruster]

Eduardo Habkost <address@hidden> writes:

> When parsing alternates from a string, there are some limitations in
> what we can do, but it is a valid use case in some situations. We can
> support booleans, integer types, and enums.
>
> This will be used to support 'feature=force' in -cpu options, while
> keeping 'feature=on|off|true|false' represented as boolean values.
>
> Signed-off-by: Eduardo Habkost <address@hidden>
> ---
>  qapi/string-input-visitor.c             | 71 ++++++++++++++++++++++----
>  tests/test-string-input-visitor.c       | 89 
> +++++++++++++++++++++++++++++++++
>  tests/qapi-schema/qapi-schema-test.json |  8 +++
>  3 files changed, 158 insertions(+), 10 deletions(-)
>
> diff --git a/qapi/string-input-visitor.c b/qapi/string-input-visitor.c
> index c089491c24..bf8f58748b 100644
> --- a/qapi/string-input-visitor.c
> +++ b/qapi/string-input-visitor.c
> @@ -19,6 +19,7 @@
>  #include "qemu/option.h"
>  #include "qemu/queue.h"
>  #include "qemu/range.h"
> +#include "qemu/bitops.h"
>  
>  
>  struct StringInputVisitor
> @@ -278,21 +279,34 @@ static void parse_type_size(Visitor *v, const char 
> *name, uint64_t *obj,
>      *obj = val;
>  }
>  
> +static int try_parse_bool(const char *s, bool *result)
> +{
> +    if (!strcasecmp(s, "on") ||
> +        !strcasecmp(s, "yes") ||
> +        !strcasecmp(s, "true")) {
> +        if (result) {
> +            *result = true;
> +        }
> +        return 0;
> +    }
> +    if (!strcasecmp(s, "off") ||
> +        !strcasecmp(s, "no") ||
> +        !strcasecmp(s, "false")) {
> +        if (result) {
> +            *result = false;
> +        }
> +        return 0;
> +    }
> +
> +    return -1;
> +}
> +
>  static void parse_type_bool(Visitor *v, const char *name, bool *obj,
>                              Error **errp)
>  {
>      StringInputVisitor *siv = to_siv(v);
>  
> -    if (!strcasecmp(siv->string, "on") ||
> -        !strcasecmp(siv->string, "yes") ||
> -        !strcasecmp(siv->string, "true")) {
> -        *obj = true;
> -        return;
> -    }
> -    if (!strcasecmp(siv->string, "off") ||
> -        !strcasecmp(siv->string, "no") ||
> -        !strcasecmp(siv->string, "false")) {
> -        *obj = false;
> +    if (try_parse_bool(siv->string, obj) == 0) {
>          return;
>      }
>  
> @@ -326,6 +340,42 @@ static void parse_type_number(Visitor *v, const char 
> *name, double *obj,
>      *obj = val;
>  }
>  
> +/* Support for alternates on string-input-visitor is limited, because

Please wing both ends of your comments, like this:

   /*
    * Comment text
    */

> + * the input string doesn't have any type information.
> + *
> + * Supported alternate member types:
> + * 1) enums
> + * 2) integer types

Better add "(but only if there 's no enum member consisting only of
digits)".

> + * 3) booleans (but only if the there's no enum variant

Make that "(but only if there's no enum member".

> + *    containing "on", "off", "true", or "false" as members)

Begs the question what happens when you violate these restrictions.

> + *
> + * UNSUPPORTED alternate member types:
> + * 1) strings
> + * 2) complex types
> + */

This comment explains the visitor's restrictions for alternate types.
It does not explain how the function works.  The proper place for
explaining the visitor's restriction is the comment in
string-input-visitor.h, which you need to update anyway, because right
now it claims visiting alternates isn't implemented.

> +static void start_alternate(Visitor *v, const char *name,
> +                            GenericAlternate **obj, size_t size,
> +                            unsigned long supported_qtypes, Error **errp)
> +{
> +    StringInputVisitor *siv = to_siv(v);
> +    QType t = QTYPE_QSTRING;

We usually call such variables @type or @qtype.

QTYPE_QSTRING means enum here.  Worth a comment, I think.

> +
> +    if (supported_qtypes & BIT(QTYPE_QBOOL)) {
> +        if (try_parse_bool(siv->string, NULL) == 0) {
> +            t = QTYPE_QBOOL;
> +        }
> +    }
> +
> +    if (supported_qtypes & BIT(QTYPE_QINT)) {
> +        if (parse_str(siv, name, NULL) == 0) {

parse_str() alters *siv.  Why is that harmless?

Aside: parse_str() is basically horrible, but that's not your fault.

> +            t = QTYPE_QINT;
> +        }
> +    }
> +
> +    *obj = g_malloc0(size);
> +    (*obj)->type = t;
> +}
> +
>  static void string_input_free(Visitor *v)
>  {
>      StringInputVisitor *siv = to_siv(v);
> @@ -353,6 +403,7 @@ Visitor *string_input_visitor_new(const char *str)
>      v->visitor.next_list = next_list;
>      v->visitor.check_list = check_list;
>      v->visitor.end_list = end_list;
> +    v->visitor.start_alternate = start_alternate;
>      v->visitor.free = string_input_free;
>  
>      v->string = str;
> diff --git a/tests/test-string-input-visitor.c 
> b/tests/test-string-input-visitor.c
> index 79313a7f7a..1e867d62c9 100644
> --- a/tests/test-string-input-visitor.c
> +++ b/tests/test-string-input-visitor.c
> @@ -290,6 +290,91 @@ static void test_visitor_in_enum(TestInputVisitorData 
> *data,
>      }
>  }
>  
> +static void test_visitor_in_alt_bool_enum(TestInputVisitorData *data,
> +                                 const void *unused)

Indentation's off.

> +{
> +    Error *err = NULL;
> +    Visitor *v;
> +    AltBoolEnum *be = NULL;
> +
> +    v = visitor_input_test_init(data, "true");
> +    visit_type_AltBoolEnum(v, NULL, &be, &err);
> +    g_assert(!err);

What's wrong with &error_abort?  More of the same below.

> +    g_assert_cmpint(be->type, ==, QTYPE_QBOOL);
> +    g_assert(be->u.b);
> +    qapi_free_AltBoolEnum(be);
> +
> +    v = visitor_input_test_init(data, "off");
> +    visit_type_AltBoolEnum(v, NULL, &be, &err);
> +    g_assert(!err);
> +    g_assert_cmpint(be->type, ==, QTYPE_QBOOL);
> +    g_assert(!be->u.b);
> +    qapi_free_AltBoolEnum(be);
> +
> +    v = visitor_input_test_init(data, "value2");
> +    visit_type_AltBoolEnum(v, NULL, &be, &err);
> +    g_assert(!err);
> +    g_assert_cmpint(be->type, ==, QTYPE_QSTRING);
> +    g_assert_cmpint(be->u.e, ==, ENUM_ONE_VALUE2);
> +    qapi_free_AltBoolEnum(be);
> +
> +    v = visitor_input_test_init(data, "value100");
> +    visit_type_AltBoolEnum(v, NULL, &be, &err);
> +    error_free_or_abort(&err);
> +    qapi_free_AltBoolEnum(be);
> +
> +    v = visitor_input_test_init(data, "10");
> +    visit_type_AltBoolEnum(v, NULL, &be, &err);
> +    error_free_or_abort(&err);
> +    qapi_free_AltBoolEnum(be);
> +}
> +
> +static void test_visitor_in_alt_enum_int(TestInputVisitorData *data,
> +                                 const void *unused)

Indentation's off.

> +{
> +    Error *err = NULL;
> +    Visitor *v;
> +    AltOnOffInt *be = NULL;
> +
> +    v = visitor_input_test_init(data, "on");
> +    visit_type_AltOnOffInt(v, NULL, &be, &err);
> +    g_assert(!err);
> +    g_assert_cmpint(be->type, ==, QTYPE_QSTRING);
> +    g_assert_cmpint(be->u.o, ==, TEST_ON_OFF_AUTO_ON);
> +    qapi_free_AltOnOffInt(be);
> +
> +    v = visitor_input_test_init(data, "off");
> +    visit_type_AltOnOffInt(v, NULL, &be, &err);
> +    g_assert(!err);
> +    g_assert_cmpint(be->type, ==, QTYPE_QSTRING);
> +    g_assert_cmpint(be->u.o, ==, TEST_ON_OFF_AUTO_OFF);
> +    qapi_free_AltOnOffInt(be);
> +
> +    v = visitor_input_test_init(data, "auto");
> +    visit_type_AltOnOffInt(v, NULL, &be, &err);
> +    g_assert(!err);
> +    g_assert_cmpint(be->type, ==, QTYPE_QSTRING);
> +    g_assert_cmpint(be->u.o, ==, TEST_ON_OFF_AUTO_AUTO);
> +    qapi_free_AltOnOffInt(be);
> +
> +    v = visitor_input_test_init(data, "-12345");
> +    visit_type_AltOnOffInt(v, NULL, &be, &err);
> +    g_assert(!err);
> +    g_assert_cmpint(be->type, ==, QTYPE_QINT);
> +    g_assert_cmpint(be->u.i, ==, -12345);
> +    qapi_free_AltOnOffInt(be);
> +
> +    v = visitor_input_test_init(data, "true");
> +    visit_type_AltOnOffInt(v, NULL, &be, &err);
> +    error_free_or_abort(&err);
> +    qapi_free_AltOnOffInt(be);
> +
> +    v = visitor_input_test_init(data, "value2");
> +    visit_type_AltOnOffInt(v, NULL, &be, &err);
> +    error_free_or_abort(&err);
> +    qapi_free_AltOnOffInt(be);
> +}
> +

Could we use tests covering alternates that don't satisfy the string
visitor's restrictions?  Like OnOffAuto + bool.

>  /* Try to crash the visitors */
>  static void test_visitor_in_fuzz(TestInputVisitorData *data,
>                                   const void *unused)
> @@ -366,6 +451,10 @@ int main(int argc, char **argv)
>                              &in_visitor_data, test_visitor_in_string);
>      input_visitor_test_add("/string-visitor/input/enum",
>                              &in_visitor_data, test_visitor_in_enum);
> +    input_visitor_test_add("/string-visitor/input/alternate/bool_enum",
> +                            &in_visitor_data, test_visitor_in_alt_bool_enum);
> +    input_visitor_test_add("/string-visitor/input/alternate/enum_int",
> +                            &in_visitor_data, test_visitor_in_alt_enum_int);
>      input_visitor_test_add("/string-visitor/input/fuzz",
>                              &in_visitor_data, test_visitor_in_fuzz);
>  
> diff --git a/tests/qapi-schema/qapi-schema-test.json 
> b/tests/qapi-schema/qapi-schema-test.json
> index 842ea3c5e3..231c8952e8 100644
> --- a/tests/qapi-schema/qapi-schema-test.json
> +++ b/tests/qapi-schema/qapi-schema-test.json
> @@ -106,6 +106,14 @@
>  { 'alternate': 'AltIntNum', 'data': { 'i': 'int', 'n': 'number' } }
>  { 'alternate': 'AltNumInt', 'data': { 'n': 'number', 'i': 'int' } }
>  
> +
> +# for testing string-input-visitor handling of alternates:
> +{ 'enum': 'TestOnOffAuto',
> +  'data': [ 'on', 'off', 'auto' ] }
> +
> +{ 'alternate': 'AltBoolEnum', 'data': { 'b': 'bool', 'e': 'EnumOne' } }
> +{ 'alternate': 'AltOnOffInt', 'data': { 'o': 'TestOnOffAuto', 'i': 'int' } }
> +
>  # for testing native lists
>  { 'union': 'UserDefNativeListUnion',
>    'data': { 'integer': ['int'],