Re: [PATCH v4] c++: Reject UDLs in certain contexts [PR105300]

[Jason Merrill <jason@redhat.com>]

On 1/13/23 18:22, Marek Polacek wrote:
> On Sat, Dec 03, 2022 at 02:58:16PM -0500, Jason Merrill wrote:
>> On 12/2/22 18:58, Marek Polacek wrote:
>>> On Fri, Nov 18, 2022 at 08:39:10PM -0500, Jason Merrill wrote:
>>>> On 11/18/22 18:52, Marek Polacek wrote:
>>>>> +/* Parse a string literal or user defined string literal.
>>>>> +
>>>>> +   user-defined-string-literal :
>>>>> +     string-literal ud-suffix
>>>>> +
>>>>> +   Parameters as for cp_parser_string_literal.  If LOOKUP_UDLIT, perform
>>>>> +   a lookup for a suitable template function.  */
>>>>> +
>>>>> +static inline cp_expr
>>>>> +cp_parser_userdef_string_literal (cp_parser *parser, bool translate,
>>>>> +				  bool wide_ok, bool lookup_udlit = true)
>>>>
>>>> I think this function doesn't need the translate and wide_ok parms, they can
>>>> always be true.
>>>
>>> I've dropped the wide_ok one, but not the other, because...
>>>>> +{
>>>>> +  return cp_parser_string_literal_common (parser, translate, wide_ok,
>>>>> +					  /*udl_ok=*/true, lookup_udlit);
>>>>> +}
>>>>> +
>>>>>     /* Look up a literal operator with the name and the exact arguments.  */
>>>>>     static tree
>>>>> @@ -4913,7 +4955,7 @@ cp_parser_userdef_numeric_literal (cp_parser *parser)
>>>>>        as arguments.  */
>>>>>     static tree
>>>>> -cp_parser_userdef_string_literal (tree literal)
>>>>> +finish_userdef_string_literal (tree literal)
>>>>>     {
>>>>>       tree suffix_id = USERDEF_LITERAL_SUFFIX_ID (literal);
>>>>>       tree name = cp_literal_operator_id (IDENTIFIER_POINTER (suffix_id));
>>>>> @@ -5652,10 +5694,10 @@ cp_parser_primary_expression (cp_parser *parser,
>>>>>         case CPP_UTF8STRING_USERDEF:
>>>>>           /* ??? Should wide strings be allowed when parser->translate_strings_p
>>>>>     	 is false (i.e. in attributes)?  If not, we can kill the third
>>>>> -	 argument to cp_parser_string_literal.  */
>>>>
>>>> I think the answer to this old question is no: if we have an
>>>> encoding-prefix, we should be translating.
>>>
>>> ...I don't actually know how to resolve this.  wide_ok is always true here.
>>> Should that change?  Or rather, should translate be false for CPP_STRING only?
> 
> Sorry it's taken so long to get back to this.
>   
>> The one current exception to my assertion above is static_assert, for which
>> we currently allow encoding-prefixes but don't translate.  I think this is
>> wrong, that we should translate the string.  But I'm not confident of that.
>>
>> But to your question, yes: when translate is false, I think we also don't
>> want to allow UDLs.  So _userdef can always pass true for translate.  And as
>> below we should call it only when translate would be true.
> 
> Done: _userdef no longer has the translate paramater and it's only called
> when parser->translate_strings_p.
>   
>> Incidentally, it seems that we set translate off for all attributes, even
>> ones that would take a normal expression argument where presumably we do
>> want translation (and UDLs).  The whole business of different parsing for
>> different attributes is a headache.  You don't need to deal with this now.
>>
>>>>> -      return (cp_parser_string_literal (parser,
>>>>> -					parser->translate_strings_p,
>>>>> -					true)
>>>>> +	 argument to cp_parser_{,userdef}string_literal.  */
>>>>> +      return (cp_parser_userdef_string_literal (parser,
>>>>> +						parser->translate_strings_p,
>>>>> +						/*wide_ok=*/true)
>>>>
>>>> For CPP_*STRING* without _USERDEF, we should still call
>>>> cp_parser_string_literal.
>>>
>>> It looks like we always have to call cp_parser_userdef_string_literal
>>> otherwise this would be reejcted:
>>>
>>>     std::string concat01 = "Hello, " "World!"_www;
>>>
>>> Because first we see a CPP_STRING but the subsequent UDL shouldn't
>>> be rejected.
>>
>> Ah, I didn't notice the function was handling a sequence of string-literals.
>> So maybe we want to call _userdef here when translate_strings_p, and not
>> when it's false.
> 
> Resolved by the change above.  Thanks,
> 
> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?

OK, thanks.

> -- >8 --
> In this PR, we are crashing because we've encountered a UDL where a
> string-literal is expected.  This patch makes the parser reject string
> and character UDLs in all places where the grammar requires a
> string-literal and not a user-defined-string-literal.
> 
> I've introduced two new wrappers; the existing cp_parser_string_literal
> was renamed to cp_parser_string_literal_common and should not be called
> directly.  finish_userdef_string_literal is renamed from
> cp_parser_userdef_string_literal.
> 
> 	PR c++/105300
> 
> gcc/c-family/ChangeLog:
> 
> 	* c-pragma.cc (handle_pragma_message): Warn for CPP_STRING_USERDEF.
> 
> gcc/cp/ChangeLog:
> 
> 	* parser.cc: Remove unnecessary forward declarations.
> 	(cp_parser_string_literal): New wrapper.
> 	(cp_parser_string_literal_common): Renamed from
> 	cp_parser_string_literal.  Add a bool parameter.  Give an error when
> 	UDLs are not permitted.
> 	(cp_parser_userdef_string_literal): New wrapper.
> 	(finish_userdef_string_literal): Renamed from
> 	cp_parser_userdef_string_literal.
> 	(cp_parser_primary_expression): Call cp_parser_userdef_string_literal
> 	instead of cp_parser_string_literal.
> 	(cp_parser_linkage_specification): Move a variable declaration closer
> 	to its first use.
> 	(cp_parser_static_assert): Likewise.
> 	(cp_parser_operator): Call cp_parser_userdef_string_literal instead of
> 	cp_parser_string_literal.
> 	(cp_parser_asm_definition): Move a variable declaration closer to its
> 	first use.
> 	(cp_parser_asm_specification_opt): Move variable declarations closer to
> 	their first use.
> 	(cp_parser_asm_operand_list): Likewise.
> 	(cp_parser_asm_clobber_list): Likewise.
> 
> gcc/testsuite/ChangeLog:
> 
> 	* g++.dg/cpp0x/udlit-error1.C: New test.
> ---
>   gcc/c-family/c-pragma.cc                  |   3 +
>   gcc/cp/parser.cc                          | 133 +++++++++++++++-------
>   gcc/testsuite/g++.dg/cpp0x/udlit-error1.C |  21 ++++
>   3 files changed, 113 insertions(+), 44 deletions(-)
>   create mode 100644 gcc/testsuite/g++.dg/cpp0x/udlit-error1.C
> 
> diff --git a/gcc/c-family/c-pragma.cc b/gcc/c-family/c-pragma.cc
> index 91fabf0a513..bba9172e8a1 100644
> --- a/gcc/c-family/c-pragma.cc
> +++ b/gcc/c-family/c-pragma.cc
> @@ -1390,6 +1390,9 @@ handle_pragma_message (cpp_reader *)
>       }
>     else if (token == CPP_STRING)
>       message = x;
> +  else if (token == CPP_STRING_USERDEF)
> +    GCC_BAD ("string literal with user-defined suffix is invalid in this "
> +	     "context");
>     else
>       GCC_BAD ("expected a string after %<#pragma message%>");
>   
> diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc
> index 8b1658decba..4b366d6c64f 100644
> --- a/gcc/cp/parser.cc
> +++ b/gcc/cp/parser.cc
> @@ -2227,16 +2227,8 @@ pop_unparsed_function_queues (cp_parser *parser)
>   
>   /* Lexical conventions [gram.lex]  */
>   
> -static cp_expr cp_parser_identifier
> -  (cp_parser *);
> -static cp_expr cp_parser_string_literal
> -  (cp_parser *, bool, bool, bool);
> -static cp_expr cp_parser_userdef_char_literal
> -  (cp_parser *);
> -static tree cp_parser_userdef_string_literal
> +static tree finish_userdef_string_literal
>     (tree);
> -static cp_expr cp_parser_userdef_numeric_literal
> -  (cp_parser *);
>   
>   /* Basic concepts [gram.basic]  */
>   
> @@ -4408,11 +4400,15 @@ cp_parser_identifier (cp_parser* parser)
>       return error_mark_node;
>   }
>   
> -/* Parse a sequence of adjacent string constants.  Returns a
> +/* Worker for cp_parser_string_literal and cp_parser_userdef_string_literal.
> +   Do not call this directly; use either of the above.
> +
> +   Parse a sequence of adjacent string constants.  Return a
>      TREE_STRING representing the combined, nul-terminated string
>      constant.  If TRANSLATE is true, translate the string to the
>      execution character set.  If WIDE_OK is true, a wide string is
> -   invalid here.
> +   valid here.  If UDL_OK is true, a string literal with user-defined
> +   suffix can be used in this context.
>   
>      C++98 [lex.string] says that if a narrow string literal token is
>      adjacent to a wide string literal token, the behavior is undefined.
> @@ -4422,9 +4418,11 @@ cp_parser_identifier (cp_parser* parser)
>      This code is largely lifted from lex_string() in c-lex.cc.
>   
>      FUTURE: ObjC++ will need to handle @-strings here.  */
> +
>   static cp_expr
> -cp_parser_string_literal (cp_parser *parser, bool translate, bool wide_ok,
> -			  bool lookup_udlit = true)
> +cp_parser_string_literal_common (cp_parser *parser, bool translate,
> +				 bool wide_ok, bool udl_ok,
> +				 bool lookup_udlit)
>   {
>     tree value;
>     size_t count;
> @@ -4449,6 +4447,12 @@ cp_parser_string_literal (cp_parser *parser, bool translate, bool wide_ok,
>   
>     if (cpp_userdef_string_p (tok->type))
>       {
> +      if (!udl_ok)
> +	{
> +	  error_at (loc, "string literal with user-defined suffix "
> +		    "is invalid in this context");
> +	  return error_mark_node;
> +	}
>         string_tree = USERDEF_LITERAL_VALUE (tok->u.value);
>         curr_type = cpp_userdef_string_remove_type (tok->type);
>         curr_tok_is_userdef_p = true;
> @@ -4539,6 +4543,12 @@ cp_parser_string_literal (cp_parser *parser, bool translate, bool wide_ok,
>   	  tok = cp_lexer_peek_token (parser->lexer);
>   	  if (cpp_userdef_string_p (tok->type))
>   	    {
> +	      if (!udl_ok)
> +		{
> +		  error_at (loc, "string literal with user-defined suffix "
> +			    "is invalid in this context");
> +		  return error_mark_node;
> +		}
>   	      string_tree = USERDEF_LITERAL_VALUE (tok->u.value);
>   	      curr_type = cpp_userdef_string_remove_type (tok->type);
>   	      curr_tok_is_userdef_p = true;
> @@ -4608,7 +4618,7 @@ cp_parser_string_literal (cp_parser *parser, bool translate, bool wide_ok,
>   	  tree literal = build_userdef_literal (suffix_id, value,
>   						OT_NONE, NULL_TREE);
>   	  if (lookup_udlit)
> -	    value = cp_parser_userdef_string_literal (literal);
> +	    value = finish_userdef_string_literal (literal);
>   	  else
>   	    value = literal;
>   	}
> @@ -4626,6 +4636,37 @@ cp_parser_string_literal (cp_parser *parser, bool translate, bool wide_ok,
>     return cp_expr (value, loc);
>   }
>   
> +/* Parse a sequence of adjacent string constants.  Return a TREE_STRING
> +   representing the combined, nul-terminated string constant.  If
> +   TRANSLATE is true, translate the string to the execution character set.
> +   If WIDE_OK is true, a wide string is valid here.
> +
> +   This function issues an error if a user defined string literal is
> +   encountered; use cp_parser_userdef_string_literal if UDLs are allowed.  */
> +
> +static inline cp_expr
> +cp_parser_string_literal (cp_parser *parser, bool translate, bool wide_ok)
> +{
> +  return cp_parser_string_literal_common (parser, translate, wide_ok,
> +					  /*udl_ok=*/false,
> +					  /*lookup_udlit=*/false);
> +}
> +
> +/* Parse a string literal or user defined string literal.
> +
> +   user-defined-string-literal :
> +     string-literal ud-suffix
> +
> +   If LOOKUP_UDLIT, perform a lookup for a suitable template function.  */
> +
> +static inline cp_expr
> +cp_parser_userdef_string_literal (cp_parser *parser, bool lookup_udlit)
> +{
> +  return cp_parser_string_literal_common (parser, /*translate=*/true,
> +					  /*wide_ok=*/true, /*udl_ok=*/true,
> +					  lookup_udlit);
> +}
> +
>   /* Look up a literal operator with the name and the exact arguments.  */
>   
>   static tree
> @@ -4923,7 +4964,7 @@ cp_parser_userdef_numeric_literal (cp_parser *parser)
>      as arguments.  */
>   
>   static tree
> -cp_parser_userdef_string_literal (tree literal)
> +finish_userdef_string_literal (tree literal)
>   {
>     tree suffix_id = USERDEF_LITERAL_SUFFIX_ID (literal);
>     tree name = cp_literal_operator_id (IDENTIFIER_POINTER (suffix_id));
> @@ -5663,10 +5704,15 @@ cp_parser_primary_expression (cp_parser *parser,
>         /* ??? Should wide strings be allowed when parser->translate_strings_p
>   	 is false (i.e. in attributes)?  If not, we can kill the third
>   	 argument to cp_parser_string_literal.  */
> -      return (cp_parser_string_literal (parser,
> -					parser->translate_strings_p,
> -					true)
> -	      .maybe_add_location_wrapper ());
> +      if (parser->translate_strings_p)
> +	return (cp_parser_userdef_string_literal (parser,
> +						  /*lookup_udlit=*/true)
> +		.maybe_add_location_wrapper ());
> +      else
> +	return (cp_parser_string_literal (parser,
> +					  /*translate=*/false,
> +					  /*wide_ok=*/true)
> +		.maybe_add_location_wrapper ());
>   
>       case CPP_OPEN_PAREN:
>         /* If we see `( { ' then we are looking at the beginning of
> @@ -16222,15 +16268,14 @@ cp_parser_function_specifier_opt (cp_parser* parser,
>   static void
>   cp_parser_linkage_specification (cp_parser* parser, tree prefix_attr)
>   {
> -  tree linkage;
> -
>     /* Look for the `extern' keyword.  */
>     cp_token *extern_token
>       = cp_parser_require_keyword (parser, RID_EXTERN, RT_EXTERN);
>   
>     /* Look for the string-literal.  */
>     cp_token *string_token = cp_lexer_peek_token (parser->lexer);
> -  linkage = cp_parser_string_literal (parser, false, false);
> +  tree linkage = cp_parser_string_literal (parser, /*translate=*/false,
> +					   /*wide_ok=*/false);
>   
>     /* Transform the literal into an identifier.  If the literal is a
>        wide-character string, or contains embedded NULs, then we can't
> @@ -16360,9 +16405,8 @@ cp_parser_static_assert(cp_parser *parser, bool member_p)
>         cp_parser_require (parser, CPP_COMMA, RT_COMMA);
>   
>         /* Parse the string-literal message.  */
> -      message = cp_parser_string_literal (parser,
> -                                	  /*translate=*/false,
> -                                	  /*wide_ok=*/true);
> +      message = cp_parser_string_literal (parser, /*translate=*/false,
> +					  /*wide_ok=*/true);
>   
>         /* A `)' completes the static assertion.  */
>         if (!parens.require_close (parser))
> @@ -17410,7 +17454,6 @@ cp_parser_operator (cp_parser* parser, location_t start_loc)
>       case CPP_STRING16_USERDEF:
>       case CPP_STRING32_USERDEF:
>         {
> -	cp_expr str;
>   	tree string_tree;
>   	int sz, len;
>   
> @@ -17418,8 +17461,8 @@ cp_parser_operator (cp_parser* parser, location_t start_loc)
>   	  maybe_warn_cpp0x (CPP0X_USER_DEFINED_LITERALS);
>   
>   	/* Consume the string.  */
> -	str = cp_parser_string_literal (parser, /*translate=*/true,
> -				      /*wide_ok=*/true, /*lookup_udlit=*/false);
> +	cp_expr str = cp_parser_userdef_string_literal (parser,
> +							/*lookup_udlit=*/false);
>   	if (str == error_mark_node)
>   	  return error_mark_node;
>   	else if (TREE_CODE (str) == USERDEF_LITERAL)
> @@ -22072,7 +22115,6 @@ cp_parser_using_directive (cp_parser* parser)
>   static void
>   cp_parser_asm_definition (cp_parser* parser)
>   {
> -  tree string;
>     tree outputs = NULL_TREE;
>     tree inputs = NULL_TREE;
>     tree clobbers = NULL_TREE;
> @@ -22180,7 +22222,8 @@ cp_parser_asm_definition (cp_parser* parser)
>     if (!cp_parser_require (parser, CPP_OPEN_PAREN, RT_OPEN_PAREN))
>       return;
>     /* Look for the string.  */
> -  string = cp_parser_string_literal (parser, false, false);
> +  tree string = cp_parser_string_literal (parser, /*translate=*/false,
> +					  /*wide_ok=*/false);
>     if (string == error_mark_node)
>       {
>         cp_parser_skip_to_closing_parenthesis (parser, true, false,
> @@ -28655,11 +28698,8 @@ cp_parser_yield_expression (cp_parser* parser)
>   static tree
>   cp_parser_asm_specification_opt (cp_parser* parser)
>   {
> -  cp_token *token;
> -  tree asm_specification;
> -
>     /* Peek at the next token.  */
> -  token = cp_lexer_peek_token (parser->lexer);
> +  cp_token *token = cp_lexer_peek_token (parser->lexer);
>     /* If the next token isn't the `asm' keyword, then there's no
>        asm-specification.  */
>     if (!cp_parser_is_keyword (token, RID_ASM))
> @@ -28672,7 +28712,9 @@ cp_parser_asm_specification_opt (cp_parser* parser)
>     parens.require_open (parser);
>   
>     /* Look for the string-literal.  */
> -  asm_specification = cp_parser_string_literal (parser, false, false);
> +  tree asm_specification = cp_parser_string_literal (parser,
> +						     /*translate=*/false,
> +						     /*wide_ok=*/false);
>   
>     /* Look for the `)'.  */
>     parens.require_close (parser);
> @@ -28705,8 +28747,6 @@ cp_parser_asm_operand_list (cp_parser* parser)
>   
>     while (true)
>       {
> -      tree string_literal;
> -      tree expression;
>         tree name;
>   
>         if (cp_lexer_next_token_is (parser->lexer, CPP_OPEN_SQUARE))
> @@ -28724,13 +28764,15 @@ cp_parser_asm_operand_list (cp_parser* parser)
>         else
>   	name = NULL_TREE;
>         /* Look for the string-literal.  */
> -      string_literal = cp_parser_string_literal (parser, false, false);
> +      tree string_literal = cp_parser_string_literal (parser,
> +						      /*translate=*/false,
> +						      /*wide_ok=*/false);
>   
>         /* Look for the `('.  */
>         matching_parens parens;
>         parens.require_open (parser);
>         /* Parse the expression.  */
> -      expression = cp_parser_expression (parser);
> +      tree expression = cp_parser_expression (parser);
>         /* Look for the `)'.  */
>         parens.require_close (parser);
>   
> @@ -28770,10 +28812,10 @@ cp_parser_asm_clobber_list (cp_parser* parser)
>   
>     while (true)
>       {
> -      tree string_literal;
> -
>         /* Look for the string literal.  */
> -      string_literal = cp_parser_string_literal (parser, false, false);
> +      tree string_literal = cp_parser_string_literal (parser,
> +						      /*translate=*/false,
> +						      /*wide_ok=*/false);
>         /* Add it to the list.  */
>         clobbers = tree_cons (NULL_TREE, string_literal, clobbers);
>         /* If the next token is not a `,', then the list is
> @@ -46345,7 +46387,9 @@ cp_parser_omp_context_selector (cp_parser *parser, tree set, bool has_parms_p)
>   		      cp_lexer_consume_token (parser->lexer);
>   		    }
>   		  else if (cp_lexer_next_token_is (parser->lexer, CPP_STRING))
> -		    value = cp_parser_string_literal (parser, false, false);
> +		    value = cp_parser_string_literal (parser,
> +						      /*translate=*/false,
> +						      /*wide_ok=*/false);
>   		  else
>   		    {
>   		      cp_parser_error (parser, "expected identifier or "
> @@ -49367,7 +49411,8 @@ pragma_lex (tree *value, location_t *loc)
>     if (ret == CPP_PRAGMA_EOL)
>       ret = CPP_EOF;
>     else if (ret == CPP_STRING)
> -    *value = cp_parser_string_literal (the_parser, false, false);
> +    *value = cp_parser_string_literal (the_parser, /*translate=*/false,
> +				       /*wide_ok=*/false);
>     else
>       {
>         if (ret == CPP_KEYWORD)
> diff --git a/gcc/testsuite/g++.dg/cpp0x/udlit-error1.C b/gcc/testsuite/g++.dg/cpp0x/udlit-error1.C
> new file mode 100644
> index 00000000000..66e300e350f
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp0x/udlit-error1.C
> @@ -0,0 +1,21 @@
> +// PR c++/105300
> +// { dg-do compile { target c++11 } }
> +
> +void operator""_x(const char *, decltype(sizeof(0)));
> +
> +#include ""_x		  // { dg-error "include expects" }
> +#line ""_x		  // { dg-error "not a positive integer" }
> +#if __has_include(""_x)	  // { dg-error "requires a header-name" }
> +#endif
> +
> +#pragma message "hi"_x	  // { dg-warning "string literal with user-defined suffix is invalid in this context" }
> +
> +extern "C"_x { void g(); } // { dg-error "before user-defined string literal" }
> +static_assert(true, "foo"_x); // { dg-error "string literal with user-defined suffix is invalid in this context|expected" }
> +
> +[[deprecated("oof"_x)]]
> +void
> +lol () // { dg-error "not a string" }
> +{
> +  asm (""_x); // { dg-error "string literal with user-defined suffix is invalid in this context" }
> +}
> 
> base-commit: 6071e495e5802a8949d2b02df6aa31a5f40f2af9