Re: [Qemu-devel] [PATCH] simpletrace: correctly detect pointers to strings

[Stefan Hajnoczi <stefanha@redhat.com>]

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On Mon, Oct 31, 2016 at 09:36:01PM +0800, Fam Zheng wrote:
> On Mon, 10/31 14:25, Paolo Bonzini wrote:
> > The visit_type_str tracepoint takes a char**, and the simpletrace backend
> > incorrectly treats that as a string.  The resulting compiler warning breaks
> > --enable-trace-backend=simple builds (including the mingw docker target).
> > Fix it by rejecting pointers to pointers to char; rewrite the detection
> > as a regular expression for simplicity.
> > 
> > Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> > ---
> >  scripts/tracetool/backend/simple.py | 8 +++-----
> >  1 file changed, 3 insertions(+), 5 deletions(-)
> > 
> > diff --git a/scripts/tracetool/backend/simple.py b/scripts/tracetool/backend/simple.py
> > index 9885e83..9dae646 100644
> > --- a/scripts/tracetool/backend/simple.py
> > +++ b/scripts/tracetool/backend/simple.py
> > @@ -14,17 +14,15 @@ __email__      = "stefanha@linux.vnet.ibm.com"
> >  
> >  
> >  from tracetool import out
> > +import re
> >  
> >  
> >  PUBLIC = True
> > +STRTYPE_RE = re.compile(r'\s*(?:const )?char\s*\*(?!\s*\*)')
> >  
> >  
> >  def is_string(arg):
> > -    strtype = ('const char*', 'char*', 'const char *', 'char *')
> > -    if arg.lstrip().startswith(strtype):
> > -        return True
> > -    else:
> > -        return False
> > +    return not (STRTYPE_RE.match(arg) is None)
> >  
> >  
> >  def generate_h_begin(events, group):
> > -- 
> > 1.8.3.1
> > 
> > 
> 
> There is already:
> 
> commit db4df20de86c6e8ecd6c9f042c029ffb9f9cddac
> Author: Fam Zheng <famz@redhat.com>
> Date:   Wed Oct 26 11:50:06 2016 +0800
> 
>     trace: Fix 'char **' compilation error in simple backend
> 
>     Currently, the generated function body will do "strlen(arg)" but the
>     argument could be 'char **' or 'char * const *'. Avoid that by excluding
>     such cases in is_string check.
> 
>     Reported by patchew's "make docker-test-mingw@fedora".
> 
>     Suggested-by: Eric Blake <eblake@redhat.com>
>     Signed-off-by: Fam Zheng <famz@redhat.com>
>     Reviewed-by: Eric Blake <eblake@redhat.com>
>     Message-id: 1477453806-21097-1-git-send-email-famz@redhat.com
>     Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

Right, I'm going to skip Paolo's patch and have double-checked that
--enable-trace-backend=simple compiles cleanly.

Stefan

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