Re: [RFA jit] initialize input_location

[David Malcolm <dmalcolm at redhat dot com>]

On Thu, 2014-03-20 at 08:53 -0600, Tom Tromey wrote:
> This patch initializes input_location at the same spot where the line
> table is initialized.  Without this, it's possible to crash when
> emitting a diagnostic in a reinvocation of the compiler, because
> input_location refers to a location that is no longer valid.
> ---
>  gcc/ChangeLog.jit | 4 ++++
>  gcc/toplev.c      | 1 +
>  2 files changed, 5 insertions(+)
> 
> diff --git a/gcc/ChangeLog.jit b/gcc/ChangeLog.jit
> index ee1df88..a9b0817 100644
> --- a/gcc/ChangeLog.jit
> +++ b/gcc/ChangeLog.jit
> @@ -1,5 +1,9 @@
>  2014-03-19  Tom Tromey  <tromey@redhat.com>
>  
> +	* toplev.c (general_init): Initialize input_location.
> +
> +2014-03-19  Tom Tromey  <tromey@redhat.com>
> +
>  	* timevar.h (auto_timevar): New class.
>  
>  2014-03-19  Tom Tromey  <tromey@redhat.com>
> diff --git a/gcc/toplev.c b/gcc/toplev.c
> index b257ab2..1febc2e 100644
> --- a/gcc/toplev.c
> +++ b/gcc/toplev.c
> @@ -1161,6 +1161,7 @@ general_init (const char *argv0)
>       table.  */
>    init_ggc ();
>    init_stringpool ();
> +  input_location = 0;
>    line_table = ggc_alloc_line_maps ();
>    linemap_init (line_table);
>    line_table->reallocator = realloc_for_line_map;

Given this declaration in input.c:
  location_t input_location;
then assigning 0 is a faithful way of resetting it to its initial state.

That said, "0" feels like a magic number.  Would it better to assign
UNKNOWN_LOCATION to it? which is 0, c.f. input.h:

  #define UNKNOWN_LOCATION ((source_location) 0)

If so, perhaps the declaration in input.c should gain an initializer to
the same value?  (shouldn't affect the code, since it's 0 either way,
but perhaps it's more readable?)

Dave