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

[Marek Polacek <polacek@redhat.com>]

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?

-- >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
-- 
2.39.0