Re: [Qemu-devel] [PATCH v6 02/23] qapi: Require int64/uint64 implementation

[Markus Armbruster]

Eric Blake <address@hidden> writes:

> Now that all visitors supply both type_int64() and type_uint64()
> callbacks, we can drop the redundant type_int() callback (the
> public interface visit_type_int() remains, but calls into
> type_int64() under the hood).
>
> Signed-off-by: Eric Blake <address@hidden>
>
> ---
> v6: new patch, but stems from v5 23/46
> ---
>  include/qapi/visitor-impl.h  |  1 -
>  qapi/opts-visitor.c          |  1 -
>  qapi/qapi-dealloc-visitor.c  |  1 -
>  qapi/qapi-visit-core.c       | 50 
> ++++++++++++++------------------------------
>  qapi/qmp-input-visitor.c     |  1 -
>  qapi/qmp-output-visitor.c    |  1 -
>  qapi/string-input-visitor.c  |  1 -
>  qapi/string-output-visitor.c |  1 -
>  8 files changed, 16 insertions(+), 41 deletions(-)
>
> diff --git a/include/qapi/visitor-impl.h b/include/qapi/visitor-impl.h
> index 44a21b7..70326e0 100644
> --- a/include/qapi/visitor-impl.h
> +++ b/include/qapi/visitor-impl.h
> @@ -36,7 +36,6 @@ struct Visitor
>      void (*get_next_type)(Visitor *v, QType *type, bool promote_int,
>                            const char *name, Error **errp);
>
> -    void (*type_int)(Visitor *v, int64_t *obj, const char *name, Error 
> **errp);
>      void (*type_bool)(Visitor *v, bool *obj, const char *name, Error **errp);
>      void (*type_str)(Visitor *v, char **obj, const char *name, Error **errp);
>      void (*type_number)(Visitor *v, double *obj, const char *name,
> diff --git a/qapi/opts-visitor.c b/qapi/opts-visitor.c
> index bc2b976..8104e42 100644
> --- a/qapi/opts-visitor.c
> +++ b/qapi/opts-visitor.c
> @@ -522,7 +522,6 @@ opts_visitor_new(const QemuOpts *opts)
>       */
>      ov->visitor.type_enum = &input_type_enum;
>
> -    ov->visitor.type_int    = &opts_type_int64;
>      ov->visitor.type_int64  = &opts_type_int64;
>      ov->visitor.type_uint64 = &opts_type_uint64;
>      ov->visitor.type_size   = &opts_type_size;
> diff --git a/qapi/qapi-dealloc-visitor.c b/qapi/qapi-dealloc-visitor.c
> index 5d1b2e6..5133d37 100644
> --- a/qapi/qapi-dealloc-visitor.c
> +++ b/qapi/qapi-dealloc-visitor.c
> @@ -220,7 +220,6 @@ QapiDeallocVisitor *qapi_dealloc_visitor_new(void)
>      v->visitor.next_list = qapi_dealloc_next_list;
>      v->visitor.end_list = qapi_dealloc_end_list;
>      v->visitor.type_enum = qapi_dealloc_type_enum;
> -    v->visitor.type_int = qapi_dealloc_type_int64;
>      v->visitor.type_int64 = qapi_dealloc_type_int64;
>      v->visitor.type_uint64 = qapi_dealloc_type_uint64;
>      v->visitor.type_bool = qapi_dealloc_type_bool;
> diff --git a/qapi/qapi-visit-core.c b/qapi/qapi-visit-core.c
> index 6d63e40..88bed9c 100644
> --- a/qapi/qapi-visit-core.c
> +++ b/qapi/qapi-visit-core.c
> @@ -97,19 +97,19 @@ void visit_type_enum(Visitor *v, int *obj, const char * 
> const strings[],
>
>  void visit_type_int(Visitor *v, int64_t *obj, const char *name, Error **errp)
>  {
> -    v->type_int(v, obj, name, errp);
> +    v->type_int64(v, obj, name, errp);
>  }
>
>  void visit_type_uint8(Visitor *v, uint8_t *obj, const char *name, Error 
> **errp)
>  {
> -    int64_t value;
> +    uint64_t value;
>
>      if (v->type_uint8) {
>          v->type_uint8(v, obj, name, errp);
>      } else {
>          value = *obj;
> -        v->type_int(v, &value, name, errp);
> -        if (value < 0 || value > UINT8_MAX) {
> +        v->type_uint64(v, &value, name, errp);
> +        if (value > UINT8_MAX) {
>              error_setg(errp, QERR_INVALID_PARAMETER_VALUE,
>                         name ? name : "null", "uint8_t");
>              return;

Note that this relies on value being in range after type_uint64() fails.
If it isn't, we call error_setg() with non-null *errp.

Two solutions:

1. Stipulate that type_uint64() & friends leave value alone on error.
   Works, because its initial value *obj is in range.

2. Avoid using value on error.  A clean way to do this:

        Error *err = NULL;

        value = *obj;
        v->type_uint64(v, &value, name, &err);
        if (err) {
            error_propagate(errp, err);
            return;
        }
        if (value < 0 || value > UINT8_MAX) {
            error_setg(errp, QERR_INVALID_PARAMETER_VALUE,
                       name ? name : "null", "uint8_t");
            return;
        }
        *obj = value;

   More boilerplate.  If we pick this solution, we'll want a separate
   PATCH 1.5 cleaning up the preexisting instances.

> @@ -120,14 +120,14 @@ void visit_type_uint8(Visitor *v, uint8_t *obj, const 
> char *name, Error **errp)
>
>  void visit_type_uint16(Visitor *v, uint16_t *obj, const char *name, Error 
> **errp)
>  {
> -    int64_t value;
> +    uint64_t value;
>
>      if (v->type_uint16) {
>          v->type_uint16(v, obj, name, errp);
>      } else {
>          value = *obj;
> -        v->type_int(v, &value, name, errp);
> -        if (value < 0 || value > UINT16_MAX) {
> +        v->type_uint64(v, &value, name, errp);
> +        if (value > UINT16_MAX) {
>              error_setg(errp, QERR_INVALID_PARAMETER_VALUE,
>                         name ? name : "null", "uint16_t");
>              return;

Good.  The fewer signed-unsigned conversions, the better.

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