Re: [PATCH 04/18] tests: print newline after QMP response in qtest logs

[Daniel P . Berrangé]

On Thu, Mar 10, 2022 at 03:11:08PM +0400, Marc-André Lureau wrote:
> Hi
> 
> On Thu, Mar 10, 2022 at 2:56 PM Daniel P. Berrangé <berrange@redhat.com>
> wrote:
> 
> > On Mon, Mar 07, 2022 at 11:09:37AM +0100, Thomas Huth wrote:
> > > On 07/03/2022 11.06, Daniel P. Berrangé wrote:
> > > > On Mon, Mar 07, 2022 at 02:51:23PM +0800, Peter Xu wrote:
> > > > > On Wed, Mar 02, 2022 at 05:49:18PM +0000, Daniel P. Berrangé wrote:
> > > > > > The QMP commands have a trailing newline, but the response does
> > not.
> > > > > > This makes the qtest logs hard to follow as the next QMP command
> > > > > > appears in the same line as the previous QMP response.
> > > > > >
> > > > > > Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
> > > > > > ---
> > > > > >   tests/qtest/libqtest.c | 3 +++
> > > > > >   1 file changed, 3 insertions(+)
> > > > > >
> > > > > > diff --git a/tests/qtest/libqtest.c b/tests/qtest/libqtest.c
> > > > > > index a85f8a6d05..79c3edcf4b 100644
> > > > > > --- a/tests/qtest/libqtest.c
> > > > > > +++ b/tests/qtest/libqtest.c
> > > > > > @@ -629,6 +629,9 @@ QDict *qmp_fd_receive(int fd)
> > > > > >           }
> > > > > >           json_message_parser_feed(&qmp.parser, &c, 1);
> > > > > >       }
> > > > > > +    if (log) {
> > > > > > +        g_assert(write(2, "\n", 1) == 1);
> > > > > > +    }
> > > > >
> > > > > Drop the g_assert() to remove side effect of G_DISABLE_ASSERT?
> > > >
> > > > You need to check the return value of write() otherwise you'll get a
> > > > compile failure due to a warn_unused_result attribute annotation.
> > > >
> > > > I don't think G_DISABLE_ASSERT is a problem as we're not defining
> > > > that in our code.
> > >
> > > You could use g_assert_true() - that's not affected by G_DISABLE_ASSERT.
> >
> > I don't think we need to do that, per existing common practice:
> >
> > $ git grep '\bg_assert('  | wc -l
> > 2912
> >
> > $ git grep '\bg_assert(' tests | wc -l
> > 2296
> >
> >
> On the topic of assert() usage, it would be nice to state clearly when to
> assert() or g_assert().
> 
> g_assert() behaviour is claimed to be more consistent than assert() across
> platforms.
> 
> Also -DNDEBUG is less obvious than -DG_DISABLE_CHECKS or -DG_DISABLE_ASSERT.

Personally I would make QEMU build error if NDEBUG or G_DISABLE_ASSERT
was defined, as running with asserts disabled will lead to unsafe code.
We rely on asserts firing to avoid compromise of QEMU when faced with
malicious data.

> I would remove assert.h and prevent from using it back, but I might be
> missing some reasons to still use it.

As a metric we've got massive use of both families of asset

$ git grep -E -o '\b(assert|g_assert(_[a-z]+)?)\b\s?\(' | sed -e 's/.*://' | 
sort | uniq -c
     17 assert (
   5196 assert(
   2913 g_assert(
     29 g_assert_cmpfloat(
    662 g_assert_cmphex(
   1745 g_assert_cmpint(
     20 g_assert_cmpmem(
    407 g_assert_cmpstr(
    756 g_assert_cmpuint(
    169 g_assert_false(
    138 g_assert_nonnull(
     22 g_assert_null(
    167 g_assert_true(

But for the tests/ subdir, g_assert family is a clear favourite

$ git grep -E -o '\b(assert|g_assert(_[a-z]+)?)\b\s?\(' tests  | sed -e 
's/.*://' | sort | uniq -c
      1 assert (
    759 assert(
   2297 g_assert(
     29 g_assert_cmpfloat(
    661 g_assert_cmphex(
   1744 g_assert_cmpint(
     20 g_assert_cmpmem(
    406 g_assert_cmpstr(
    754 g_assert_cmpuint(
    169 g_assert_false(
    138 g_assert_nonnull(
     22 g_assert_null(
    167 g_assert_true(


This split doesn't appear to have changed all that much over time.
Going back to v3.0.0 we see similar ballpark figures

$ git grep -E -o '\b(assert|g_assert(_[a-z]+)?)\b\s?\(' | sed -e 's/.*://' | 
sort | uniq -c 
     18 assert (
   3766 assert(
   2210 g_assert(
     23 g_assert_cmpfloat(
    310 g_assert_cmphex(
   1352 g_assert_cmpint(
     11 g_assert_cmpmem(
    324 g_assert_cmpstr(
    489 g_assert_cmpuint(
     88 g_assert_false(
     73 g_assert_nonnull(
      8 g_assert_null(
     46 g_assert_true(
[berrange@catbus qemu]$ git grep -E -o '\b(assert|g_assert(_[a-z]+)?)\b\s?\(' 
tests | sed -e 's/.*://' | sort | uniq -c 
    566 assert(
   1876 g_assert(
     23 g_assert_cmpfloat(
    309 g_assert_cmphex(
   1351 g_assert_cmpint(
     10 g_assert_cmpmem(
    323 g_assert_cmpstr(
    488 g_assert_cmpuint(
     88 g_assert_false(
     73 g_assert_nonnull(
      8 g_assert_null(
     46 g_assert_true(


Removing either 'assert' or g_assert would be a massive amount of code
churn, for no real functional benefit.

I would personally encourage the more specific g_assert_* variants, to
improve the error messages, but that's really minor.

IMHO we can accept that all of the above are valid to use and worry
about more important things.

With regards,
Daniel
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