Re: [PATCH 2/5] c++: Set the locus of the function result decl

[Jason Merrill <jason@redhat.com>]

On 11/12/22 13:45, Bernhard Reutner-Fischer wrote:
> gcc/cp/ChangeLog:
> 
> 	* decl.cc (start_function): Set the result decl source location to
> 	the location of the typespec.
> 
> ---
> Bootstrapped and regtested on x86_86-unknown-linux with no regressions.
> Ok for trunk?
> 
> Cc: Nathan Sidwell <nathan@acm.org>
> Cc: Jason Merrill <jason@redhat.com>
> ---
>   gcc/cp/decl.cc | 15 ++++++++++++++-
>   1 file changed, 14 insertions(+), 1 deletion(-)
> 
> diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
> index 6e98ea35a39..ed40815e645 100644
> --- a/gcc/cp/decl.cc
> +++ b/gcc/cp/decl.cc
> @@ -17449,6 +17449,8 @@ start_function (cp_decl_specifier_seq *declspecs,
>   		tree attrs)
>   {
>     tree decl1;
> +  tree result;
> +  bool ret;

We now prefer to declare new variables as late as possible, usually when 
they are initialized.

>     decl1 = grokdeclarator (declarator, declspecs, FUNCDEF, 1, &attrs);
>     invoke_plugin_callbacks (PLUGIN_START_PARSE_FUNCTION, decl1);
> @@ -17461,7 +17463,18 @@ start_function (cp_decl_specifier_seq *declspecs,
>       gcc_assert (same_type_p (TREE_TYPE (TREE_TYPE (decl1)),
>   			     integer_type_node));
>   
> -  return start_preparsed_function (decl1, attrs, /*flags=*/SF_DEFAULT);
> +  ret = start_preparsed_function (decl1, attrs, /*flags=*/SF_DEFAULT);
> +
> +  /* decl1 might be ggc_freed here.  */
> +  decl1 = current_function_decl;
> +
> +  /* Set the result decl source location to the location of the typespec.  */
> +  if (TREE_CODE (decl1) == FUNCTION_DECL
> +      && declspecs->locations[ds_type_spec] != UNKNOWN_LOCATION
> +      && (result = DECL_RESULT (decl1)) != NULL_TREE
> +      && DECL_SOURCE_LOCATION (result) == input_location)
> +    DECL_SOURCE_LOCATION (result) = declspecs->locations[ds_type_spec];

One way to handle the template case would be for the code in 
start_preparsed_function that sets DECL_RESULT to check whether decl1 is 
a template instantiation, and in that case copy the location from the 
template's DECL_RESULT, i.e.

DECL_RESULT (DECL_TEMPLATE_RESULT (DECL_TI_TEMPLATE (decl1)))

> +  return ret;
>   }
>   \f
>   /* Returns true iff an EH_SPEC_BLOCK should be created in the body of