Re: [Qemu-devel] [PATCH 03/14] qerror: drop qerror_abort()

[Markus Armbruster <armbru@redhat.com>]

Luiz Capitulino <lcapitulino@redhat.com> writes:

> Previously, developers had to create error dicts manually and also enter
> the matching desc table entry. Thus, qerro_abort() was added to help

s/qerro_/qerror_/

> catching bad error dicts.
>
> Today, all that stuff is generated automatically which makes the chance
> of a bad generated dict quite low.

The generator can only generate well-formed dicts, right?

> Also, qerror_abort() would... _abort_ on a bad error dict!

In my opinion, it's perfectly fine to abort on a programming error.

> This commit maintains the same verification logic on the error object
> but drops the abort() in favor of reporting UndefinedError for bad dicts
> (and also print a debug message to stderr).

I certainly won't object to your elaborate handling, but me, I'd simply
replace qerror_abort() by straight abort() and be done with it *shrug*

> Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
> ---
>  qerror.c | 83 +++++++++++++++++++++++++++++++++++-----------------------------
>  1 file changed, 46 insertions(+), 37 deletions(-)
>
> diff --git a/qerror.c b/qerror.c
> index d428b52..74b3659 100644
> --- a/qerror.c
> +++ b/qerror.c
> @@ -38,55 +38,50 @@ static QError *qerror_new(void)
>      return qerr;
>  }
>  
> -static void GCC_FMT_ATTR(2, 3) qerror_abort(const QError *qerr,
> -                                            const char *fmt, ...)
> -{
> -    va_list ap;
> -
> -    fprintf(stderr, "qerror: bad call in function '%s':\n", qerr->func);
> -    fprintf(stderr, "qerror: -> ");
> -
> -    va_start(ap, fmt);
> -    vfprintf(stderr, fmt, ap);
> -    va_end(ap);
> -
> -    fprintf(stderr, "\nqerror: call at %s:%d\n", qerr->file, qerr->linenr);
> -    abort();
> -}
> -
> -static void GCC_FMT_ATTR(2, 0) qerror_set_data(QError *qerr,
> -                                               const char *fmt, va_list *va)
> +static QDict *error_object_from_fmt(const char *fmt, va_list *va)
>  {
>      QObject *obj;
> +    QDict *ret;
>  
>      obj = qobject_from_jsonv(fmt, va);
>      if (!obj) {
> -        qerror_abort(qerr, "invalid format '%s'", fmt);
> +        fprintf(stderr, "invalid json in error dict '%s'\n", fmt);
> +        return NULL;
>      }
>      if (qobject_type(obj) != QTYPE_QDICT) {
> -        qerror_abort(qerr, "error format is not a QDict '%s'", fmt);
> +        fprintf(stderr, "error is not a dict '%s'\n", fmt);
> +        goto out_free;
>      }
>  
> -    qerr->error = qobject_to_qdict(obj);
> -
> -    obj = qdict_get(qerr->error, "class");
> +    ret = qobject_to_qdict(obj);
> +    obj = qdict_get(ret, "class");
>      if (!obj) {
> -        qerror_abort(qerr, "missing 'class' key in '%s'", fmt);
> +        fprintf(stderr, "missing 'class' key in '%s'\n", fmt);
> +        goto out_free;
>      }
>      if (qobject_type(obj) != QTYPE_QSTRING) {
> -        qerror_abort(qerr, "'class' key value should be a QString");
> +        fprintf(stderr, "'class' key value should be a string in '%s'\n", fmt);
> +        goto out_free;
>      }
> -    
> -    obj = qdict_get(qerr->error, "data");
> +
> +    obj = qdict_get(ret, "data");
>      if (!obj) {
> -        qerror_abort(qerr, "missing 'data' key in '%s'", fmt);
> +        fprintf(stderr, "missing 'data' key in '%s'\n", fmt);
> +        goto out_free;
>      }
>      if (qobject_type(obj) != QTYPE_QDICT) {
> -        qerror_abort(qerr, "'data' key value should be a QDICT");
> +        fprintf(stderr, "'data' key value should be a dict in '%s'\n", fmt);
> +        goto out_free;
>      }
> +
> +    return ret;
> +
> +out_free:
> +    qobject_decref(obj);
> +    return NULL;
>  }
>  
> -static void qerror_set_desc(QError *qerr, const char *fmt)
> +static const QErrorStringTable *error_get_desc(const char *fmt)
>  {
>      int i;
>  
> @@ -94,12 +89,17 @@ static void qerror_set_desc(QError *qerr, const char *fmt)
>  
>      for (i = 0; qerror_table[i].error_fmt; i++) {
>          if (strcmp(qerror_table[i].error_fmt, fmt) == 0) {
> -            qerr->entry = &qerror_table[i];
> -            return;
> +            return &qerror_table[i];
>          }
>      }
>  
> -    qerror_abort(qerr, "error format '%s' not found", fmt);
> +    fprintf(stderr, "error format '%s' not found\n", fmt);
> +    return NULL;
> +}
> +
> +static QDict *build_error_no_arg(const char *fmt)
> +{
> +    return qobject_to_qdict(qobject_from_jsonv(fmt, NULL));
>  }
>  
>  /**
> @@ -127,13 +127,22 @@ static QError *qerror_from_info(const char *file, int linenr, const char *func,
>      qerr->file = file;
>      qerr->func = func;
>  
> -    if (!fmt) {
> -        qerror_abort(qerr, "QDict not specified");
> +    qerr->error = error_object_from_fmt(fmt, va);
> +    if (!qerr->error) {
> +        goto bad_err;
> +    }
> +
> +    qerr->entry = error_get_desc(fmt);
> +    if (!qerr->entry) {
> +        QDECREF(qerr->error);
> +        goto bad_err;
>      }
>  
> -    qerror_set_data(qerr, fmt, va);
> -    qerror_set_desc(qerr, fmt);
> +    return qerr;
>  
> +bad_err:
> +    qerr->error = build_error_no_arg(QERR_UNDEFINED_ERROR);

Nit: defeats gcc's format checking.  This shouldn't:

       qerr->error = qobject_to_qdict(qobject_from_json(QERR_UNDEFINED_ERROR));

> +    qerr->entry = error_get_desc(QERR_UNDEFINED_ERROR);
>      return qerr;
>  }