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Re: [Qemu-devel] [PATCH 4/7] qapi: String visitor, use %f represenation
From: |
Michael Roth |
Subject: |
Re: [Qemu-devel] [PATCH 4/7] qapi: String visitor, use %f represenation for floats |
Date: |
Fri, 11 May 2012 12:32:02 -0500 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Fri, May 11, 2012 at 01:34:01PM -0300, Luiz Capitulino wrote:
> On Fri, 27 Apr 2012 15:21:20 -0500
> Michael Roth <address@hidden> 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 <address@hidden>
> > ---
> > 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?
Well, object_property_print() is the only string-output-visitor user,
and it's not currently used. I don't see this changing for 1.1, so this
can probably wait.
>
> > }
> >
> > 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);
> > }
> >
>