[PR 80005] Fix __has_include

__has_include is funky in that it is macro-like from the POV of #ifdef and
friends, but lexes its parenthesize argument #include-like.  We were
failing the second part of that, because we used a forwarding macro to an
internal name, and hence always lexed the argument in macro-parameter
context.  We componded that by not setting the right flag when lexing, so
it didn't even know.  Mostly users got lucky.

This reimplements the handline.
1) Remove the forwarding, but declare object-like macros that
expand to themselves.  This satisfies the #ifdef requirement

2) Correctly set angled_brackets when lexing the parameter.  This tells
the lexer (a) <...> is a header name and (b) "..." is too (not a string).

3) Remove the in__has_include lexer state, just tell find_file that that's
what's happenning, so it doesn't emit an error.

We lose the (undocumented) ability to #undef __has_include.  That may well
have been an accident of implementation.  There are no tests for it.

We gain __has_include behaviour for all users of the preprocessors -- not
just the C-family ones that defined a forwarding macro.

	libcpp/
	PR preprocessor/80005
	* include/cpplib.h (BT_HAS_ATTRIBUTE): Fix comment.
	* internal.h (struct lexer_state): Delete in__has_include field.
	(struct spec_nodes): Rename n__has_include{,_next}__ fields.
	(_cpp_defined_macro_p): New.
	(_cpp_find_file): Add has_include parm.
	* directives.c (lex_macro_node): Combine defined,
	__has_inline{,_next} checking.
	(do_ifdef, do_ifndef): Use _cpp_defined_macro_p.
	(_cpp_init_directives): Refactor.
	* expr.c (parse_defined): Use _cpp_defined_macro_p.
	(eval_token): Adjust parse_has_include calls.
	(parse_has_include): Add OP parameter.  Reimplement.
	* files.c (_cpp_find_file): Add HAS_INCLUDE parm.  Use it to
	inhibit error message.
	(_cpp_stack_include): Adjust _cpp_find_file call.
	(_cpp_fake_include, _cpp_compare_file_date): Likewise.
	(open_file_failed): Remove in__has_include check.
	(_cpp_has_header): Adjust _cpp_find_file call.
	* identifiers.c (_cpp_init_hashtable): Don't init
	__has_include{,_next} here ...
	* init.c (cpp_init_builtins): ... init them here.  Define as
	macros.
	(cpp_read_main_file): Adjust _cpp_find_file call.
	* pch.c (cpp_read_state): Adjust __has_include{,_next} access.
	* traditional.c (_cpp_scan_out_locgical_line): Likewise.

	gcc/c-family/
	PR preprocessor/80005
	* c-cppbuiltins.c (c_cpp_builtins): Don't define __has_include{,_next}.

	gcc/testsuite/
	PR preprocessor/80005
	* g++.dg/cpp1y/feat-cxx14.C: Adjust.
	* g++.dg/cpp1z/feat-cxx17.C: Adjust.
	* g++.dg/cpp2a/feat-cxx2a.C: Adjust.
	* g++.dg/cpp/pr80005.C: New.

10 files changed, 103 insertions, 65 deletions

diff --git a/libcpp/ChangeLog b/libcpp/ChangeLog
index 3249b93fe88..27a841bbdce 100644
--- a/libcpp/ChangeLog
+++ b/libcpp/ChangeLog
@@ -1,4 +1,31 @@
-2020-01-17  Nathan Sidwell  <nathan@acm.org>
+2020-01-20  Nathan Sidwell  <nathan@acm.org>
+
+	PR preprocessor/80005
+	* include/cpplib.h (BT_HAS_ATTRIBUTE): Fix comment.
+	* internal.h (struct lexer_state): Delete in__has_include field.
+	(struct spec_nodes): Rename n__has_include{,_next}__ fields.
+	(_cpp_defined_macro_p): New.
+	(_cpp_find_file): Add has_include parm.
+	* directives.c (lex_macro_node): Combine defined,
+	__has_inline{,_next} checking.
+	(do_ifdef, do_ifndef): Use _cpp_defined_macro_p.
+	(_cpp_init_directives): Refactor.
+	* expr.c (parse_defined): Use _cpp_defined_macro_p.
+	(eval_token): Adjust parse_has_include calls.
+	(parse_has_include): Add OP parameter.  Reimplement.
+	* files.c (_cpp_find_file): Add HAS_INCLUDE parm.  Use it to
+	inhibit error message.
+	(_cpp_stack_include): Adjust _cpp_find_file call.
+	(_cpp_fake_include, _cpp_compare_file_date): Likewise.
+	(open_file_failed): Remove in__has_include check.
+	(_cpp_has_header): Adjust _cpp_find_file call.
+	* identifiers.c (_cpp_init_hashtable): Don't init
+	__has_include{,_next} here ...
+	* init.c (cpp_init_builtins): ... init them here.  Define as
+	macros.
+	(cpp_read_main_file): Adjust _cpp_find_file call.
+	* pch.c (cpp_read_state): Adjust __has_include{,_next} access.
+	* traditional.c (_cpp_scan_out_locgical_line): Likewise.
 
 	PR preprocessor/93306
 	* expr.c (parse_has_include): Refactor.  Check skip_eval before
diff --git a/libcpp/directives.c b/libcpp/directives.c
index 983206a5838..10735c8c668 100644
--- a/libcpp/directives.c
+++ b/libcpp/directives.c
@@ -595,14 +595,13 @@ lex_macro_node (cpp_reader *pfile, bool is_def_or_undef)
     {
       cpp_hashnode *node = token->val.node.node;
 
-      if (is_def_or_undef && node == pfile->spec_nodes.n_defined)
+      if (is_def_or_undef
+	  && (node == pfile->spec_nodes.n_defined
+	      || node == pfile->spec_nodes.n__has_include
+	      || node == pfile->spec_nodes.n__has_include_next))
 	cpp_error (pfile, CPP_DL_ERROR,
-		   "\"defined\" cannot be used as a macro name");
-      else if (is_def_or_undef
-	    && (node == pfile->spec_nodes.n__has_include__
-	     || node == pfile->spec_nodes.n__has_include_next__))
-	cpp_error (pfile, CPP_DL_ERROR,
-		   "\"__has_include__\" cannot be used as a macro name");
+		   "\"%s\" cannot be used as a macro name",
+		   NODE_NAME (node));
       else if (! (node->flags & NODE_POISONED))
 	return node;
     }
@@ -1966,11 +1965,7 @@ do_ifdef (cpp_reader *pfile)
 
       if (node)
 	{
-	  /* Do not treat conditional macros as being defined.  This is due to
-	     the powerpc port using conditional macros for 'vector', 'bool',
-	     and 'pixel' to act as conditional keywords.  This messes up tests
-	     like #ifndef bool.  */
-	  skip = !cpp_macro_p (node) || (node->flags & NODE_CONDITIONAL);
+	  skip = !_cpp_defined_macro_p (node);
 	  _cpp_mark_macro_used (node);
 	  _cpp_maybe_notify_macro_use (pfile, node);
 	  if (pfile->cb.used)
@@ -1999,8 +1994,7 @@ do_ifndef (cpp_reader *pfile)
 	     the powerpc port using conditional macros for 'vector', 'bool',
 	     and 'pixel' to act as conditional keywords.  This messes up tests
 	     like #ifndef bool.  */
-	  skip = (cpp_macro_p (node)
-		  && !(node->flags & NODE_CONDITIONAL));
+	  skip = _cpp_defined_macro_p (node);
 	  _cpp_mark_macro_used (node);
 	  _cpp_maybe_notify_macro_use (pfile, node);
 	  if (pfile->cb.used)
@@ -2638,12 +2632,9 @@ _cpp_pop_buffer (cpp_reader *pfile)
 void
 _cpp_init_directives (cpp_reader *pfile)
 {
-  unsigned int i;
-  cpp_hashnode *node;
-
-  for (i = 0; i < (unsigned int) N_DIRECTIVES; i++)
+  for (int i = 0; i < N_DIRECTIVES; i++)
     {
-      node = cpp_lookup (pfile, dtable[i].name, dtable[i].length);
+      cpp_hashnode *node = cpp_lookup (pfile, dtable[i].name, dtable[i].length);
       node->is_directive = 1;
       node->directive_index = i;
     }
diff --git a/libcpp/expr.c b/libcpp/expr.c
index 317faf50208..df21a4b9fb9 100644
--- a/libcpp/expr.c
+++ b/libcpp/expr.c
@@ -64,7 +64,7 @@ static unsigned int interpret_float_suffix (cpp_reader *, const uchar *, size_t)
 static unsigned int interpret_int_suffix (cpp_reader *, const uchar *, size_t);
 static void check_promotion (cpp_reader *, const struct op *);
 
-static cpp_num parse_has_include (cpp_reader *, enum include_type);
+static cpp_num parse_has_include (cpp_reader *, cpp_hashnode *, include_type);
 
 /* Token type abuse to create unary plus and minus operators.  */
 #define CPP_UPLUS ((enum cpp_ttype) (CPP_LAST_CPP_OP + 1))
@@ -1088,8 +1088,7 @@ parse_defined (cpp_reader *pfile)
   result.unsignedp = false;
   result.high = 0;
   result.overflow = false;
-  result.low = (node && cpp_macro_p (node)
-		&& !(node->flags & NODE_CONDITIONAL));
+  result.low = node && _cpp_defined_macro_p (node);
   return result;
 }
 
@@ -1160,10 +1159,10 @@ eval_token (cpp_reader *pfile, const cpp_token *token,
     case CPP_NAME:
       if (token->val.node.node == pfile->spec_nodes.n_defined)
 	return parse_defined (pfile);
-      else if (token->val.node.node == pfile->spec_nodes.n__has_include__)
-	return parse_has_include (pfile, IT_INCLUDE);
-      else if (token->val.node.node == pfile->spec_nodes.n__has_include_next__)
-	return parse_has_include (pfile, IT_INCLUDE_NEXT);
+      else if (token->val.node.node == pfile->spec_nodes.n__has_include)
+	return parse_has_include (pfile, token->val.node.node, IT_INCLUDE);
+      else if (token->val.node.node == pfile->spec_nodes.n__has_include_next)
+	return parse_has_include (pfile, token->val.node.node, IT_INCLUDE_NEXT);
       else if (CPP_OPTION (pfile, cplusplus)
 	       && (token->val.node.node == pfile->spec_nodes.n_true
 		   || token->val.node.node == pfile->spec_nodes.n_false))
@@ -2190,9 +2189,9 @@ num_div_op (cpp_reader *pfile, cpp_num lhs, cpp_num rhs, enum cpp_ttype op,
   return lhs;
 }
 
-/* Handle meeting "__has_include__" in a preprocessor expression.  */
+/* Handle meeting "__has_include" in a preprocessor expression.  */
 static cpp_num
-parse_has_include (cpp_reader *pfile, enum include_type type)
+parse_has_include (cpp_reader *pfile, cpp_hashnode *op, include_type type)
 {
   cpp_num result;
 
@@ -2201,12 +2200,15 @@ parse_has_include (cpp_reader *pfile, enum include_type type)
   result.overflow = false;
   result.low = 0;
 
-  pfile->state.in__has_include__++;
-
+  pfile->state.angled_headers = true;
   const cpp_token *token = cpp_get_token (pfile);
   bool paren = token->type == CPP_OPEN_PAREN;
   if (paren)
     token = cpp_get_token (pfile);
+  else
+    cpp_error (pfile, CPP_DL_ERROR,
+	       "missing '(' before \"%s\" operand", NODE_NAME (op));
+  pfile->state.angled_headers = false;
 
   bool bracket = token->type != CPP_STRING;
   cpp_hashnode *node = NULL;
@@ -2222,7 +2224,7 @@ parse_has_include (cpp_reader *pfile, enum include_type type)
     fname = _cpp_bracket_include (pfile);
   else
     cpp_error (pfile, CPP_DL_ERROR,
-	       "operator \"__has_include__\" requires a header string");
+	       "operator \"%s\" requires a header-name", NODE_NAME (op));
 
   if (fname)
     {
@@ -2237,14 +2239,10 @@ parse_has_include (cpp_reader *pfile, enum include_type type)
 
   if (paren && !SEEN_EOL () && cpp_get_token (pfile)->type != CPP_CLOSE_PAREN)
     cpp_error (pfile, CPP_DL_ERROR,
-	       "missing ')' after \"__has_include__\"");
+	       "missing ')' after \"%s\" operand", NODE_NAME (op));
 
-  /* A possible controlling macro of the form #if !__has_include__ ().
-     _cpp_parse_expr checks there was no other junk on the line.  */
   if (node)
     pfile->mi_ind_cmacro = node;
 
-  pfile->state.in__has_include__--;
-
   return result;
 }
diff --git a/libcpp/files.c b/libcpp/files.c
index 7abae7ae6ec..260e787c329 100644
--- a/libcpp/files.c
+++ b/libcpp/files.c
@@ -504,7 +504,8 @@ _cpp_find_failed (_cpp_file *file)
 
 _cpp_file *
 _cpp_find_file (cpp_reader *pfile, const char *fname, cpp_dir *start_dir,
-		bool fake, int angle_brackets, bool implicit_preinclude,
+		int angle_brackets,
+		bool fake, bool implicit_preinclude, bool has_include,
 		location_t loc)
 {
   struct cpp_file_hash_entry *entry;
@@ -592,7 +593,8 @@ _cpp_find_file (cpp_reader *pfile, const char *fname, cpp_dir *start_dir,
 		return NULL;
 	      }
 
-	    open_file_failed (pfile, file, angle_brackets, loc);
+	    if (!has_include)
+	      open_file_failed (pfile, file, angle_brackets, loc);
 	    break;
 	  }
 
@@ -1046,8 +1048,8 @@ _cpp_stack_include (cpp_reader *pfile, const char *fname, int angle_brackets,
   if (!dir)
     return false;
 
-  _cpp_file *file = _cpp_find_file (pfile, fname, dir, false, angle_brackets,
-				    type == IT_DEFAULT, loc);
+  _cpp_file *file = _cpp_find_file (pfile, fname, dir, angle_brackets,
+				    false, type == IT_DEFAULT, false, loc);
   if (type == IT_DEFAULT && file == NULL)
     return false;
 
@@ -1062,9 +1064,6 @@ open_file_failed (cpp_reader *pfile, _cpp_file *file, int angle_brackets,
   int sysp = pfile->line_table->highest_line > 1 && pfile->buffer ? pfile->buffer->sysp : 0;
   bool print_dep = CPP_OPTION (pfile, deps.style) > (angle_brackets || !!sysp);
 
-  if (pfile->state.in__has_include__)
-    return;
-
   errno = file->err_no;
   if (print_dep && CPP_OPTION (pfile, deps.missing_files) && errno == ENOENT)
     {
@@ -1343,7 +1342,8 @@ cpp_clear_file_cache (cpp_reader *pfile)
 void
 _cpp_fake_include (cpp_reader *pfile, const char *fname)
 {
-  _cpp_find_file (pfile, fname, pfile->buffer->file->dir, true, 0, false, 0);
+  _cpp_find_file (pfile, fname, pfile->buffer->file->dir,
+		  0, true, false, false, 0);
 }
 
 /* Not everyone who wants to set system-header-ness on a buffer can
@@ -1461,7 +1461,8 @@ _cpp_compare_file_date (cpp_reader *pfile, const char *fname,
   if (!dir)
     return -1;
 
-  file = _cpp_find_file (pfile, fname, dir, false, angle_brackets, false, 0);
+  file = _cpp_find_file (pfile, fname, dir, angle_brackets,
+			 false, false, false, 0);
   if (file->err_no)
     return -1;
 
@@ -2004,9 +2005,11 @@ _cpp_has_header (cpp_reader *pfile, const char *fname, int angle_brackets,
 		 enum include_type type)
 {
   cpp_dir *start_dir = search_path_head (pfile, fname, angle_brackets, type);
-  _cpp_file *file = _cpp_find_file (pfile, fname, start_dir,
-				    /*fake=*/false, angle_brackets,
-				    /*implicit_preinclude=*/false, 0);
+  _cpp_file *file = _cpp_find_file (pfile, fname, start_dir, angle_brackets,
+				    /*fake=*/false,
+				    /*implicit_preinclude=*/false,
+				    /*has_include=*/true,
+				    0);
   return file->err_no != ENOENT;
 }
 
diff --git a/libcpp/identifiers.c b/libcpp/identifiers.c
index 562d8fee3b5..9627e1bf4b0 100644
--- a/libcpp/identifiers.c
+++ b/libcpp/identifiers.c
@@ -72,8 +72,7 @@ _cpp_init_hashtable (cpp_reader *pfile, cpp_hash_table *table)
   s->n__VA_ARGS__->flags |= NODE_DIAGNOSTIC;
   s->n__VA_OPT__        = cpp_lookup (pfile, DSC("__VA_OPT__"));
   s->n__VA_OPT__->flags |= NODE_DIAGNOSTIC;
-  s->n__has_include__   = cpp_lookup (pfile, DSC("__has_include__"));
-  s->n__has_include_next__ = cpp_lookup (pfile, DSC("__has_include_next__"));
+  /* __has_include{,_next} are inited in cpp_init_builtins.  */
 }
 
 /* Tear down the identifier hash table.  */
diff --git a/libcpp/include/cpplib.h b/libcpp/include/cpplib.h
index 1c26c365347..56cbbd82750 100644
--- a/libcpp/include/cpplib.h
+++ b/libcpp/include/cpplib.h
@@ -859,7 +859,7 @@ enum cpp_builtin_type
   BT_PRAGMA,			/* `_Pragma' operator */
   BT_TIMESTAMP,			/* `__TIMESTAMP__' */
   BT_COUNTER,			/* `__COUNTER__' */
-  BT_HAS_ATTRIBUTE,		/* `__has_attribute__(x)' */
+  BT_HAS_ATTRIBUTE,		/* `__has_attribute(x)' */
   BT_HAS_BUILTIN		/* `__has_builtin(x)' */
 };
 
diff --git a/libcpp/init.c b/libcpp/init.c
index 2b4923e1451..e798140ef8b 100644
--- a/libcpp/init.c
+++ b/libcpp/init.c
@@ -578,6 +578,17 @@ cpp_init_builtins (cpp_reader *pfile, int hosted)
 
   if (CPP_OPTION (pfile, objc))
     _cpp_define_builtin (pfile, "__OBJC__ 1");
+
+  /* These two behave as macros for #ifdef, but are evaluated
+     specially inside #if.  */
+  _cpp_define_builtin (pfile, "__has_include __has_include");
+  _cpp_define_builtin (pfile, "__has_include_next __has_include_next");
+  pfile->spec_nodes.n__has_include
+    = cpp_lookup (pfile, DSC("__has_include"));
+  pfile->spec_nodes.n__has_include->flags |= NODE_DIAGNOSTIC;
+  pfile->spec_nodes.n__has_include_next
+    = cpp_lookup (pfile, DSC("__has_include_next"));
+  pfile->spec_nodes.n__has_include_next->flags |= NODE_DIAGNOSTIC;
 }
 
 /* Sanity-checks are dependent on command-line options, so it is
@@ -672,7 +683,8 @@ cpp_read_main_file (cpp_reader *pfile, const char *fname)
     }
 
   pfile->main_file
-    = _cpp_find_file (pfile, fname, &pfile->no_search_path, false, 0, false,
+    = _cpp_find_file (pfile, fname, &pfile->no_search_path, /*angle=*/0,
+		      /*fake=*/false, /*preinclude=*/false, /*hasinclude=*/false,
 		      loc);
   if (_cpp_find_failed (pfile->main_file))
     return NULL;
diff --git a/libcpp/internal.h b/libcpp/internal.h
index 3623baf8191..5453c3bff85 100644
--- a/libcpp/internal.h
+++ b/libcpp/internal.h
@@ -268,9 +268,6 @@ struct lexer_state
   /* Nonzero when parsing arguments to a function-like macro.  */
   unsigned char parsing_args;
 
-  /* Nonzero if in a __has_include__ or __has_include_next__ statement.  */
-  unsigned char in__has_include__;
-
   /* Nonzero if prevent_expansion is true only because output is
      being discarded.  */
   unsigned char discarding_output;
@@ -293,8 +290,8 @@ struct spec_nodes
   cpp_hashnode *n_false;		/* C++ keyword false */
   cpp_hashnode *n__VA_ARGS__;		/* C99 vararg macros */
   cpp_hashnode *n__VA_OPT__;		/* C++ vararg macros */
-  cpp_hashnode *n__has_include__;	/* __has_include__ operator */
-  cpp_hashnode *n__has_include_next__;	/* __has_include_next__ operator */
+  cpp_hashnode *n__has_include;		/* __has_include operator */
+  cpp_hashnode *n__has_include_next;	/* __has_include_next operator */
 };
 
 typedef struct _cpp_line_note _cpp_line_note;
@@ -641,6 +638,16 @@ cpp_in_primary_file (cpp_reader *pfile)
   return pfile->line_table->depth == 1;
 }
 
+/* True if NODE is a macro for the purposes of ifdef, defined etc.  */
+inline bool _cpp_defined_macro_p (cpp_hashnode *node)
+{
+  /* Do not treat conditional macros as being defined.  This is due to
+     the powerpc port using conditional macros for 'vector', 'bool',
+     and 'pixel' to act as conditional keywords.  This messes up tests
+     like #ifndef bool.  */
+  return cpp_macro_p (node) && !(node->flags & NODE_CONDITIONAL);
+}
+
 /* In macro.c */
 extern void _cpp_notify_macro_use (cpp_reader *pfile, cpp_hashnode *node);
 inline void _cpp_maybe_notify_macro_use (cpp_reader *pfile, cpp_hashnode *node)
@@ -674,7 +681,8 @@ extern void _cpp_destroy_hashtable (cpp_reader *);
 /* In files.c */
 typedef struct _cpp_file _cpp_file;
 extern _cpp_file *_cpp_find_file (cpp_reader *, const char *, cpp_dir *,
-				  bool, int, bool, location_t);
+				  int angle, bool fake, bool preinclude,
+				  bool has_include, location_t);
 extern bool _cpp_find_failed (_cpp_file *);
 extern void _cpp_mark_file_once_only (cpp_reader *, struct _cpp_file *);
 extern void _cpp_fake_include (cpp_reader *, const char *);
diff --git a/libcpp/pch.c b/libcpp/pch.c
index 607f805bebe..e631050936b 100644
--- a/libcpp/pch.c
+++ b/libcpp/pch.c
@@ -811,8 +811,8 @@ cpp_read_state (cpp_reader *r, const char *name, FILE *f,
     s->n_false		= cpp_lookup (r, DSC("false"));
     s->n__VA_ARGS__     = cpp_lookup (r, DSC("__VA_ARGS__"));
     s->n__VA_OPT__      = cpp_lookup (r, DSC("__VA_OPT__"));
-    s->n__has_include__ = cpp_lookup (r, DSC("__has_include__"));
-    s->n__has_include_next__ = cpp_lookup (r, DSC("__has_include_next__"));
+    s->n__has_include   = cpp_lookup (r, DSC("__has_include"));
+    s->n__has_include_next = cpp_lookup (r, DSC("__has_include_next"));
   }
 
   old_state = r->state;
diff --git a/libcpp/traditional.c b/libcpp/traditional.c
index 21c63b47dd5..ff06d31a897 100644
--- a/libcpp/traditional.c
+++ b/libcpp/traditional.c
@@ -78,8 +78,8 @@ enum ls {ls_none = 0,		/* Normal state.  */
 	 ls_hash,		/* After # in preprocessor conditional.  */
 	 ls_predicate,		/* After the predicate, maybe paren?  */
 	 ls_answer,		/* In answer to predicate.  */
-	 ls_has_include,	/* After __has_include__.  */
-	 ls_has_include_close};	/* Looking for ')' of __has_include__.  */
+	 ls_has_include,	/* After __has_include.  */
+	 ls_has_include_close};	/* Looking for ')' of __has_include.  */
 
 /* Lexing TODO: Maybe handle space in escaped newlines.  Stop lex.c
    from recognizing comments and directives during its lexing pass.  */
@@ -565,8 +565,8 @@ _cpp_scan_out_logical_line (cpp_reader *pfile, cpp_macro *macro,
 		  continue;
 		}
 	      else if (pfile->state.in_expression
-		       && (node == pfile->spec_nodes.n__has_include__
-			|| node == pfile->spec_nodes.n__has_include_next__))
+		       && (node == pfile->spec_nodes.n__has_include
+			|| node == pfile->spec_nodes.n__has_include_next))
 		{
 		  lex_state = ls_has_include;
 		  continue;