Re: [Qemu-devel] [PATCH 4/7] qapi: String visitor, use %f represenation for floats

[Luiz Capitulino <lcapitulino@redhat.com>]

On Fri, 27 Apr 2012 15:21:20 -0500
Michael Roth <mdroth@linux.vnet.ibm.com> wrote:

> Currently string-output-visitor formats floats as %g, which is nice in
> that trailing 0's are automatically truncated, but otherwise this causes
> some issues:
> 
>  - it 6 uses significant figures instead of 6 decimal places, which
>    means something like 155777.5 (which even has an exact floating point
>    representation) will be rounded to 155778 when converted to a string.
> 
>  - output will be presented in scientific notation when the normalized
>    form requires a 10^x multiplier. Not a huge deal, but arguably less
>    readable for command-line arguments.
> 
>  - due to using sig figs instead of hard-defined decimal places, it
>    fails a lot of the test-visitor-serialization unit tests for floats.
> 
> Instead, let's just use %f, which is what the QJSON and the QMP visitors
> use.
> 
> Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
> ---
>  qapi/string-output-visitor.c       |    2 +-
>  tests/test-string-output-visitor.c |    2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/qapi/string-output-visitor.c b/qapi/string-output-visitor.c
> index 92b0305..34e525e 100644
> --- a/qapi/string-output-visitor.c
> +++ b/qapi/string-output-visitor.c
> @@ -52,7 +52,7 @@ static void print_type_number(Visitor *v, double *obj, const char *name,
>                                Error **errp)
>  {
>      StringOutputVisitor *sov = DO_UPCAST(StringOutputVisitor, visitor, v);
> -    string_output_set(sov, g_strdup_printf("%g", *obj));
> +    string_output_set(sov, g_strdup_printf("%f", *obj));

Doesn't look like a bug fix worth it for 1.1, am I wrong?

>  }
>  
>  char *string_output_get_string(StringOutputVisitor *sov)
> diff --git a/tests/test-string-output-visitor.c b/tests/test-string-output-visitor.c
> index 22909b8..608f14a 100644
> --- a/tests/test-string-output-visitor.c
> +++ b/tests/test-string-output-visitor.c
> @@ -84,7 +84,7 @@ static void test_visitor_out_number(TestOutputVisitorData *data,
>  
>      str = string_output_get_string(data->sov);
>      g_assert(str != NULL);
> -    g_assert_cmpstr(str, ==, "3.14");
> +    g_assert_cmpstr(str, ==, "3.140000");
>      g_free(str);
>  }
>