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.

2 files changed, 21 insertions, 0 deletions

diff --git a/gcc/testsuite/c-c++-common/cpp/pr93452-1.c b/gcc/testsuite/c-c++-common/cpp/pr93452-1.c
new file mode 100644
index 0000000..f0986e4
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/cpp/pr93452-1.c
@@ -0,0 +1,10 @@
+/* { dg-do preprocess } */
+/* { dg-additional-options "-fdirectives-only" } */
+
+int main ()
+{
+  return 0;
+}
+
+/* A regexp that doesn't match itself!  */
+/* { dg-final { scan-file-not pr93452-1.i {_[_]has_include} } } */
diff --git a/gcc/testsuite/c-c++-common/cpp/pr93452-2.c b/gcc/testsuite/c-c++-common/cpp/pr93452-2.c
new file mode 100644
index 0000000..c9ab0e9
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/cpp/pr93452-2.c
@@ -0,0 +1,11 @@
+/* { dg-do preprocess } */
+/* { dg-additional-options "-dD" } */
+
+#if __has_include ("who cares" )
+#endif
+int main ()
+{
+  return 0;
+}
+
+/* { dg-final { scan-file-not pr93452-2.i {__has_include} } } */