Re: [PATCH 2 PR gdb/16959] gdb hangs in infinite recursion

[Wei-min Pan <weimin dot pan at oracle dot com>]

On 3/22/2018 1:27 PM, Simon Marchi wrote:
> On 2018-03-22 01:41 PM, Weimin Pan wrote:
> > The original problem was fixed (see related PR 22242). But using a typedef
> > as the declared type for a static member variable, as commented in this PR,
> > is still causing gdb to get into infinite loop when printing the static
> > member's value. This problem can be reproduced as follows:
> >
> > % cat t.cc
> > class A {
> >      typedef A type;
> > public:
> >      bool operator==(const type& other) { return true; }
> >
> >      static const type INSTANCE;
> > };
> >
> > const A A::INSTANCE;
> >
> > int main() {
> >      A a;
> >      if (a == A::INSTANCE) {
> >          return -1;
> >      }
> >      return 0;
> > }
> > % g++ -g t.cc
> > % gdb -ex "start" -ex "p a" a.out
> >
> > The fix is rather trivial - in cp_print_static_field(), should call
> > check_typedef() to get the static member's real type and use it to
> > check whether it's a struct or an array.
> >
> > Added a new test case to the testsuite as Simon suggested.
> >
> > Tested on both aarch64-linux-gnu and amd64-linux-gnu. No regressions.
> > ---
> > ---
> >   gdb/ChangeLog                                 |    7 ++++
> >   gdb/cp-valprint.c                             |    2 +-
> >   gdb/testsuite/ChangeLog                       |    5 +++
> >   gdb/testsuite/gdb.cp/static-typedef-print.cc  |   35 +++++++++++++++++++++
> >   gdb/testsuite/gdb.cp/static-typedef-print.exp |   40 +++++++++++++++++++++++++
> >   5 files changed, 88 insertions(+), 1 deletions(-)
> >   create mode 100644 gdb/testsuite/gdb.cp/static-typedef-print.cc
> >   create mode 100644 gdb/testsuite/gdb.cp/static-typedef-print.exp
> >
> > diff --git a/gdb/ChangeLog b/gdb/ChangeLog
> > index d0a8dfd..6fd43de 100644
> > --- a/gdb/ChangeLog
> > +++ b/gdb/ChangeLog
> > @@ -1,3 +1,10 @@
> > +2018-02-07  Weimin Pan  <weimin.pan@oracle.com>
> > +
> > +	PR gdb/16959
> > +	* cp-valprint.c: (cp_print_static_field) Use check_typedef() to get
> > +	static member's real type for TYPE_CODE_STRUCT and TYPE_CODE_ARRAY
> > +	comparisons.
> > +
> >   2018-01-24  Pedro Alves  <palves@redhat.com>
> >   
> >   	GCC PR libstdc++/83906
> > diff --git a/gdb/cp-valprint.c b/gdb/cp-valprint.c
> > index 486653f..0370b56 100644
> > --- a/gdb/cp-valprint.c
> > +++ b/gdb/cp-valprint.c
> > @@ -633,6 +633,7 @@ cp_print_static_field (struct type *type,
> >         return;
> >       }
> >   
> > +  type = check_typedef (type);
> >     if (TYPE_CODE (type) == TYPE_CODE_STRUCT)
> >       {
> >         CORE_ADDR *first_dont_print;
> > @@ -658,7 +659,6 @@ cp_print_static_field (struct type *type,
> >         addr = value_address (val);
> >         obstack_grow (&dont_print_statmem_obstack, (char *) &addr,
> >   		    sizeof (CORE_ADDR));
> > -      type = check_typedef (type);
> >         cp_print_value_fields (type, value_enclosing_type (val),
> >   			     value_embedded_offset (val), addr,
> >   			     stream, recurse, val,
> I pointed this out in my previous mail:
>
> type is passed below to val_print.  I think it would be better to continue
> passing the original type to that function instead of the resolved type.  It
> could affect how things are printed (if the type name is printed somewhere,
> or if pretty printers are involved).  Many functions use a variable "real_type"
> to hold the result from check_typedef, you could follow that pattern.
>
> Did you have a chance to take a look?
>
> Simon

Sorry, I missed it. Will take a look.

Thanks,
Weimin