[PATCH] Fix crash in cp_print_value_fields

[Tom de Vries]

On 17-05-19 22:18, Tom Tromey wrote:
> From: Tom Tromey <tom@tromey.com>
> 
> PR c++/20020 concerns a crash in cp_print_value_fields.  The immediate
> cause is that cp_print_value_fields does not handle the case where
> value_static_field fails.  This is fixed in this patch by calling
> cp_print_static_field from the "try" block.
> 
> Digging a bit deeper, the error occurs because GCC does not emit a
> DW_AT_const_value for a static constexpr member appearing in a
> template class.  I've filed a GCC bug for this.
> 
> Tested on x86-64 Fedora 29.
> 
> gdb/ChangeLog
> 2019-05-17  Tom Tromey  <tromey@adacore.com>
> 
> 	PR c++/20020:
> 	* cp-valprint.c (cp_print_value_fields): Call
> 	cp_print_static_field inside "try".
> 
> gdb/testsuite/ChangeLog
> 2019-05-17  Tom Tromey  <tromey@adacore.com>
> 
> 	PR c++/20020:
> 	* gdb.cp/constexpr-field.exp: New file.
> 	* gdb.cp/constexpr-field.cc: New file.
> ---
>  gdb/ChangeLog                            |  6 ++++
>  gdb/cp-valprint.c                        | 12 ++++----
>  gdb/testsuite/ChangeLog                  |  6 ++++
>  gdb/testsuite/gdb.cp/constexpr-field.cc  | 37 ++++++++++++++++++++++++
>  gdb/testsuite/gdb.cp/constexpr-field.exp | 36 +++++++++++++++++++++++
>  5 files changed, 90 insertions(+), 7 deletions(-)
>  create mode 100644 gdb/testsuite/gdb.cp/constexpr-field.cc
>  create mode 100644 gdb/testsuite/gdb.cp/constexpr-field.exp
> 
> diff --git a/gdb/cp-valprint.c b/gdb/cp-valprint.c
> index ff860df499a..d8d5c06fd1e 100644
> --- a/gdb/cp-valprint.c
> +++ b/gdb/cp-valprint.c
> @@ -329,22 +329,20 @@ cp_print_value_fields (struct type *type, struct type *real_type,
>  		}
>  	      else if (field_is_static (&TYPE_FIELD (type, i)))
>  		{
> -		  struct value *v = NULL;
> -
>  		  try
>  		    {
> -		      v = value_static_field (type, i);
> -		    }
> +		      struct value *v = value_static_field (type, i);
>  
> +		      cp_print_static_field (TYPE_FIELD_TYPE (type, i),
> +					     v, stream, recurse + 1,
> +					     options);
> +		    }

Here options is used ...

>  		  catch (const gdb_exception_error &ex)
>  		    {
>  		      fprintf_filtered (stream,
>  					_("<error reading variable: %s>"),
>  					ex.what ());
>  		    }
> -
> -		  cp_print_static_field (TYPE_FIELD_TYPE (type, i),
> -					 v, stream, recurse + 1, opts);

while here opts used to be used.

Is this change intentional? It's not mentioned anywhere.

Thanks,
- Tom

>  		}
>  	      else if (i == vptr_fieldno && type == vptr_basetype)
>  		{