ping^1 Re: [PATCH] Objective-C++ : Fix handling of unnamed message parms [PR49070].

[Iain Sandoe]

Although this is an Objective-C++ patch, I need to touch stuff outside  
“objc local”
contexts, so think it needs review,

(this is a regression fix for all open branches).

Iain Sandoe <iain@sandoe.co.uk> wrote:

> We were discussing proposed reflection splicing syntax - [:reflection:]  
> in SG7
> which has some similarities with objective-c++ message syntax with unnamed
> params.
>
> This reminded me that we have a *very* long-standing regression against
> objective-c++ where it is not able to handle unnamed message parameters (an
> idiom used in practice).
>
> Fixed as below.
> tested on x86_64-darwin, x86_64-linux-gnu,
> OK for master / open branches?
>
> thanks
> Iain
>
> ------
>
> When we are parsing an Objective-C++ message, a colon is a valid
> terminator for a assignment-expression.  That is:
>
> [receiver meth:x:x:x:x];
>
> Is a valid, if somewhat unreadable, construction; corresponding
> to a method declaration like:
>
> - (id) meth:(id)arg0 :(id)arg1 :(id)arg2 :(id)arg3;
>
> Where three of the message params have no name.
>
> If fact, although it might be unintentional, Objective-C/C++ can
> accept message selectors with all the parms unnamed (this applies
> to the clang implementation too, which is taken as the reference
> for the language).
>
> For regular C++, the pattern x:x is not valid in that position an
> an error is emitted with a fixit for the expected scope token.
>
> If we simply made that error conditional on !c_c_dialect_objc()
> that would regress Objective-C++ diagnostics for cases outside a
> message selector, so we add a state flag for this.
>
> gcc/cp/ChangeLog:
>
> 	PR objc++/49070
> 	* parser.c (cp_debug_parser): Add Objective-C++ message
> 	state flag.
> 	(cp_parser_nested_name_specifier_opt): Allow colon to
> 	terminate an assignment-expression when parsing Objective-
> 	C++ messages.
> 	(cp_parser_objc_message_expression): Set and clear message
> 	parsing state on entry and exit.
> 	* parser.h (struct cp_parser): Add a context flag for
> 	Objective-C++ message state.
>
> gcc/testsuite/ChangeLog:
>
> 	PR objc++/49070
> 	* obj-c++.dg/pr49070.mm: New test.
> 	* objc.dg/unnamed-parms.m: New test.
> ---
> gcc/cp/parser.c                       |  8 ++++-
> gcc/cp/parser.h                       |  4 +++
> gcc/testsuite/obj-c++.dg/pr49070.mm   | 52 +++++++++++++++++++++++++++
> gcc/testsuite/objc.dg/unnamed-parms.m | 28 +++++++++++++++
> 4 files changed, 91 insertions(+), 1 deletion(-)
> create mode 100644 gcc/testsuite/obj-c++.dg/pr49070.mm
> create mode 100644 gcc/testsuite/objc.dg/unnamed-parms.m
>
> diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
> index 70775792161..e5ba1dcffaa 100644
> --- a/gcc/cp/parser.c
> +++ b/gcc/cp/parser.c
> @@ -572,6 +572,8 @@ cp_debug_parser (FILE *file, cp_parser *parser)
> 			      parser->colon_corrects_to_scope_p);
>   cp_debug_print_flag (file, "Colon doesn't start a class definition",
> 			      parser->colon_doesnt_start_class_def_p);
> +  cp_debug_print_flag (file, "Parsing an Objective-C++ message context",
> +			      parser->objective_c_message_context_p);
>   if (parser->type_definition_forbidden_message)
>     fprintf (file, "Error message for forbidden type definitions: %s %s\n",
> 	     parser->type_definition_forbidden_message,
> @@ -6622,7 +6624,9 @@ cp_parser_nested_name_specifier_opt (cp_parser  
> *parser,
>
> 	  if (token->type == CPP_COLON
> 	      && parser->colon_corrects_to_scope_p
> -	      && cp_lexer_peek_nth_token (parser->lexer, 3)->type == CPP_NAME)
> +	      && cp_lexer_peek_nth_token (parser->lexer, 3)->type == CPP_NAME
> +	      /* name:name is a valid sequence in an Objective C message.  */
> +	      && !parser->objective_c_message_context_p)
> 	    {
> 	      gcc_rich_location richloc (token->location);
> 	      richloc.add_fixit_replace ("::");
> @@ -32965,6 +32969,7 @@ cp_parser_objc_message_expression (cp_parser*  
> parser)
> {
>   tree receiver, messageargs;
>
> +  parser->objective_c_message_context_p = true;
>   location_t start_loc = cp_lexer_peek_token (parser->lexer)->location;
>   cp_lexer_consume_token (parser->lexer);  /* Eat '['.  */
>   receiver = cp_parser_objc_message_receiver (parser);
> @@ -32981,6 +32986,7 @@ cp_parser_objc_message_expression (cp_parser*  
> parser)
>   location_t combined_loc = make_location (start_loc, start_loc, end_loc);
>   protected_set_expr_location (result, combined_loc);
>
> +  parser->objective_c_message_context_p = false;
>   return result;
> }
>
> diff --git a/gcc/cp/parser.h b/gcc/cp/parser.h
> index d587cf2404b..a468b6992ad 100644
> --- a/gcc/cp/parser.h
> +++ b/gcc/cp/parser.h
> @@ -350,6 +350,10 @@ struct GTY(()) cp_parser {
>      is terminated by colon.  */
>   bool colon_doesnt_start_class_def_p;
>
> +  /* TRUE if we are parsing an objective c message, and ':' is permitted
> +     to terminate an assignment-expression.  */
> +  bool objective_c_message_context_p;
> +
>   /* If non-NULL, then we are parsing a construct where new type
>      definitions are not permitted.  The string stored here will be
>      issued as an error message if a type is defined.  */
> diff --git a/gcc/testsuite/obj-c++.dg/pr49070.mm  
> b/gcc/testsuite/obj-c++.dg/pr49070.mm
> new file mode 100644
> index 00000000000..d67c72137cc
> --- /dev/null
> +++ b/gcc/testsuite/obj-c++.dg/pr49070.mm
> @@ -0,0 +1,52 @@
> +/* Only needs to compile.  */
> +/* { dg-additional-options "-std=c++11" } */
> +
> +#ifdef __cplusplus
> +enum X {
> +  x = 5,
> +  y
> +};
> +#endif
> +
> +__attribute__((__objc_root_class__))
> +@interface A
> +- (id) :(id)arg0 :(id)arg1;
> +- (id) m:(id)arg0 :(id)arg1 :(id)arg2 :(id)arg3;
> +#ifdef __cplusplus
> +- (id) n:(X)arg0 :(X)arg1 :(id)arg2 :(id)arg3;
> +#endif
> +@end
> +
> +@implementation A
> +- (id) :(id)arg0 :(id)arg1
> +{
> +  return arg1;
> +}
> +- (id) m:(id)arg0 :(id)arg1 :(id)arg2 :(id)arg3
> +{
> +  return arg2;
> +}
> +#ifdef __cplusplus
> +- (id) n:(X)arg0 :(X)arg1 :(id)arg2 :(id)arg3
> +{
> +  return arg2;
> +}
> +#endif
> +@end
> +
> +id f1 (A *x)
> +{
> +  return [x:x:x];
> +}
> +
> +id f2 (A *x)
> +{
> +  return [x m:x:x:x:x];
> +}
> +
> +#ifdef __cplusplus
> +id f3 (A *x)
> +{
> +  return [x n:X::x:X::y:x:x];
> +}
> +#endif
> diff --git a/gcc/testsuite/objc.dg/unnamed-parms.m  
> b/gcc/testsuite/objc.dg/unnamed-parms.m
> new file mode 100644
> index 00000000000..22426cfed5f
> --- /dev/null
> +++ b/gcc/testsuite/objc.dg/unnamed-parms.m
> @@ -0,0 +1,28 @@
> +/* Only needs to compile [see PR 49070 for C++ issue].  */
> +
> +__attribute__((__objc_root_class__))
> +@interface A
> +- (id) :(id)arg0 :(id)arg1;
> +- (id) m:(id)arg0 :(id)arg1 :(id)arg2 :(id)arg3;
> +@end
> +
> +@implementation A
> +- (id) :(id)arg0 :(id)arg1
> +{
> +  return arg1;
> +}
> +- (id) m:(id)arg0 :(id)arg1 :(id)arg2 :(id)arg3
> +{
> +  return arg2;
> +}
> +@end
> +
> +id f1 (A *x)
> +{
> +  return [x:x:x];
> +}
> +
> +id f2 (A *x)
> +{
> +  return [x m:x:x:x:x];
> +}
> -- 
> 2.24.1