[PATCH] c++: Member initializer list diagnostic locations [PR94024]

[Jason Merrill]

On 8/3/20 10:14 AM, Patrick Palka wrote:
> This patch preserves the source locations of each node in a member
> initializer list so that during processing of the list we can set
> input_location appropriately for generally more accurate diagnostic
> locations.  Since TREE_LIST nodes are tcc_exceptional, they can't have
> source locations, so we instead store the location in a dummy
> tcc_expression node within the TREE_TYPE of the list node.

> Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK to
> commit?
> 
> gcc/cp/ChangeLog:
> 
> 	PR c++/94024
> 	* init.c (sort_mem_initializers): Preserve TREE_TYPE of the
> 	member initializer list node.
> 	(emit_mem_initializers): Set input_location when performing each
> 	member initialization.
> 	* parser.c (cp_parser_mem_initializer_list): Attach the source
> 	location of this initializer to a dummy EMPTY_CLASS_EXPR within
> 	the TREE_TYPE of the list node.
> 	* pt.c (tsubst_initializer_list): Preserve TREE_TYPE of the
> 	member initializer list node.
> 
> gcc/testsuite/ChangeLog:
> 
> 	PR c++/94024
> 	* g++.dg/diagnostic/mem-init1.C: New test.
> ---
>   gcc/cp/init.c                               |  6 +++++
>   gcc/cp/parser.c                             |  8 ++++++
>   gcc/cp/pt.c                                 |  3 +++
>   gcc/testsuite/g++.dg/diagnostic/mem-init1.C | 29 +++++++++++++++++++++
>   4 files changed, 46 insertions(+)
>   create mode 100644 gcc/testsuite/g++.dg/diagnostic/mem-init1.C
> 
> diff --git a/gcc/cp/init.c b/gcc/cp/init.c
> index cb9bd2dbfba..3f089404cf2 100644
> --- a/gcc/cp/init.c
> +++ b/gcc/cp/init.c
> @@ -1151,6 +1151,8 @@ sort_mem_initializers (tree t, tree mem_inits)
>   
>         /* Record the initialization.  */
>         TREE_VALUE (subobject_init) = TREE_VALUE (init);
> +      /* Carry over the dummy TREE_TYPE node containing the source location.  */
> +      TREE_TYPE (subobject_init) = TREE_TYPE (init);
>         next_subobject = subobject_init;
>       }
>   
> @@ -1367,6 +1369,10 @@ emit_mem_initializers (tree mem_inits)
>     /* Initialize the data members.  */
>     while (mem_inits)
>       {
> +      /* If this initializer was explicitly provided, then the dummy TREE_TYPE
> +	 node contains the source location.  */
> +      iloc_sentinel ils (EXPR_LOCATION (TREE_TYPE (mem_inits)));
> +
>         perform_member_init (TREE_PURPOSE (mem_inits),
>   			   TREE_VALUE (mem_inits));
>         mem_inits = TREE_CHAIN (mem_inits);
> diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
> index ab088874ba7..2f9b8786121 100644
> --- a/gcc/cp/parser.c
> +++ b/gcc/cp/parser.c
> @@ -15326,6 +15326,14 @@ cp_parser_mem_initializer_list (cp_parser* parser)
>   	{
>   	  TREE_CHAIN (mem_initializer) = mem_initializer_list;
>   	  mem_initializer_list = mem_initializer;
> +
> +	  /* We can't attach the source location of this initializer directly to
> +	     the list node, so we instead attach it to a dummy EMPTY_CLASS_EXPR
> +	     within the TREE_TYPE of the list node.  */
> +	  TREE_TYPE (mem_initializer) = build0 (EMPTY_CLASS_EXPR, NULL_TREE);
> +	  SET_EXPR_LOCATION (TREE_TYPE (mem_initializer),
> +			     make_location (token->location,
> +					    token->location, input_location));

Why not do this in cp_parser_mem_initializer?

Also, use parser->lexer for the last argument to make_location.

>   	}
>         /* If the next token is not a `,', we're done.  */
>         if (cp_lexer_next_token_is_not (parser->lexer, CPP_COMMA))
> diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
> index 3a168d506cf..bed1a3532e7 100644
> --- a/gcc/cp/pt.c
> +++ b/gcc/cp/pt.c
> @@ -26014,6 +26014,9 @@ tsubst_initializer_list (tree t, tree argvec)
>             if (decl)
>               {
>                 init = build_tree_list (decl, init);
> +	      /* Carry over the dummy TREE_TYPE node containing the source
> +		 location.  */
> +	      TREE_TYPE (init) = TREE_TYPE (t);
>                 TREE_CHAIN (init) = inits;
>                 inits = init;
>               }
> diff --git a/gcc/testsuite/g++.dg/diagnostic/mem-init1.C b/gcc/testsuite/g++.dg/diagnostic/mem-init1.C
> new file mode 100644
> index 00000000000..b749c72cd8b
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/diagnostic/mem-init1.C
> @@ -0,0 +1,29 @@
> +// PR c++/94024
> +// { dg-do compile }
> +
> +struct A {
> +    A()
> +    : a()       // { dg-error "reference type" }
> +    , b(1)      // { dg-error "incompatible" }
> +    , c(0)      // { dg-bogus "" }
> +    {}
> +
> +    int &a;
> +    int b[1];
> +    char c;
> +};
> +
> +template<typename T, typename U>
> +struct B {
> +    B()
> +    : a()       // { dg-error "reference type" }
> +    , b(1)      // { dg-error "incompatible" }
> +    , c(0)      // { dg-bogus "" }
> +    {}
> +
> +    T a;
> +    U b;
> +    char c;
> +};
> +
> +B<int&, int[1]> b;
>