preprocessor: Make __has_include a builtin macro [PR93452]

The clever hack of '#define __has_include __has_include' breaks -dD
and -fdirectives-only, because that emits definitions.  This turns
__has_include into a proper builtin macro.  Thus it's never emitted
via -dD, and because use outside of directive processing is undefined,
we can just expand it anywhere.

	PR preprocessor/93452
	* internal.h (struct spec_nodes): Drop n__has_include{,_next}.
	* directives.c (lex_macro_node): Don't check __has_include redef.
	* expr.c (eval_token): Drop __has_include eval.
	(parse_has_include): Move to ...
	* macro.c (builtin_has_include): ... here.
	(_cpp_builtin_macro_text): Eval __has_include{,_next}.
	* include/cpplib.h (enum cpp_builtin_type): Add BT_HAS_INCLUDE{,_NEXT}.
	* init.c (builtin_array): Add them.
	(cpp_init_builtins): Drop __has_include{,_next} init here ...
	* pch.c (cpp_read_state): ... and here.
	* traditional.c (enum ls): Drop has_include states ...
	(_cpp_scan_out_logical_line): ... and here.

1 files changed, 56 insertions, 0 deletions

diff --git a/libcpp/macro.c b/libcpp/macro.c
index dbd7a28..ec3f8b7 100644
--- a/libcpp/macro.c
+++ b/libcpp/macro.c
@@ -336,6 +336,56 @@ unsigned num_expanded_macros_counter = 0;
    from macro expansion.  */
 unsigned num_macro_tokens_counter = 0;
 
+/* Handle meeting "__has_include" builtin macro.  */
+
+static int
+builtin_has_include (cpp_reader *pfile, cpp_hashnode *op, bool has_next)
+{
+  int result = 0;
+
+  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;
+  char *fname = NULL;
+  if (token->type == CPP_STRING || token->type == CPP_HEADER_NAME)
+    {
+      fname = XNEWVEC (char, token->val.str.len - 1);
+      memcpy (fname, token->val.str.text + 1, token->val.str.len - 2);
+      fname[token->val.str.len - 2] = '\0';
+    }
+  else if (token->type == CPP_LESS)
+    fname = _cpp_bracket_include (pfile);
+  else
+    cpp_error (pfile, CPP_DL_ERROR,
+	       "operator \"%s\" requires a header-name", NODE_NAME (op));
+
+  if (fname)
+    {
+      /* Do not do the lookup if we're skipping, that's unnecessary
+	 IO.  */
+      if (!pfile->state.skip_eval
+	  && _cpp_has_header (pfile, fname, bracket,
+			      has_next ? IT_INCLUDE_NEXT : IT_INCLUDE))
+	result = 1;
+
+      XDELETEVEC (fname);
+    }
+
+  if (paren && !SEEN_EOL () && cpp_get_token (pfile)->type != CPP_CLOSE_PAREN)
+    cpp_error (pfile, CPP_DL_ERROR,
+	       "missing ')' after \"%s\" operand", NODE_NAME (op));
+
+  return result;
+}
+
 /* Emits a warning if NODE is a macro defined in the main file that
    has not been used.  */
 int
@@ -572,6 +622,12 @@ _cpp_builtin_macro_text (cpp_reader *pfile, cpp_hashnode *node,
     case BT_HAS_BUILTIN:
       number = pfile->cb.has_builtin (pfile);
       break;
+
+    case BT_HAS_INCLUDE:
+    case BT_HAS_INCLUDE_NEXT:
+      number = builtin_has_include (pfile, node,
+				    node->value.builtin == BT_HAS_INCLUDE_NEXT);
+      break;
     }
 
   if (result == NULL)