[preprocessor] Include stacking

https://gcc.gnu.org/ml/gcc-patches/2019-08/msg01971.html
	* internal.h (enum include_type): Add IT_MAIN, IT_DIRECTIVE_HWM,
	IT_HEADER_HWM.
	(_cpp_stack_file): Take include_type, not a bool.
	* files.c (_cpp_find_file): Refactor to not hide an if inside a
	for conditional.
	(should_stack_file): Break apart to ...
	(is_known_idempotent_file, has_unique_contents): ... these.
	(_cpp_stack_file): Replace IMPORT boolean with include_type enum.
	Refactor to use new predicates.  Do linemap compensation here ...
	(_cpp_stack_include): ... not here.
	* init.c (cpp_read_main_file): Pass IT_MAIN to _cpp_stack_file.

From-SVN: r275034

libcpp/ChangeLog

+2019-08-29  Nathan Sidwell  <nathan@acm.org>
+
+	* internal.h (enum include_type): Add IT_MAIN, IT_DIRECTIVE_HWM,
+	IT_HEADER_HWM.
+	(_cpp_stack_file): Take include_type, not a bool.
+	* files.c (_cpp_find_file): Refactor to not hide an if inside a
+	for conditional.
+	(should_stack_file): Break apart to ...
+	(is_known_idempotent_file, has_unique_contents): ... these.
+	(_cpp_stack_file): Replace IMPORT boolean with include_type enum.
+	Refactor to use new predicates.  Do linemap compensation here ...
+	(_cpp_stack_include): ... not here.
+	* init.c (cpp_read_main_file): Pass IT_MAIN to _cpp_stack_file.
+
 2019-08-28  Nathan Sidwell  <nathan@acm.org>
 
 	* directives-only.c (_cpp_preprocess_dir_only): Use false, not

libcpp/init.c

@@ -651,7 +651,7 @@ cpp_read_main_file (cpp_reader *pfile, const char *fname)
   if (_cpp_find_failed (pfile->main_file))
     return NULL;
 
-  _cpp_stack_file (pfile, pfile->main_file, false, loc);
+  _cpp_stack_file (pfile, pfile->main_file, IT_MAIN, 0);
 
   /* For foo.i, read the original filename foo.c now, for the benefit
      of the front ends.  */

libcpp/internal.h

@@ -123,6 +123,10 @@ enum include_type
    /* Non-directive including mechanisms.  */
    IT_CMDLINE,  /* -include */
    IT_DEFAULT,  /* forced header  */
+   IT_MAIN,     /* main  */
+
+   IT_DIRECTIVE_HWM = IT_IMPORT + 1,  /* Directives below this.  */
+   IT_HEADER_HWM = IT_DEFAULT + 1,    /* Header files below this.  */
   };
 
 union utoken
@@ -671,8 +675,7 @@ extern _cpp_file *_cpp_find_file (cpp_reader *, const char *, cpp_dir *,
 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 *);
-extern bool _cpp_stack_file (cpp_reader *, _cpp_file*, bool,
-			     location_t);
+extern bool _cpp_stack_file (cpp_reader *, _cpp_file*, include_type, location_t);
 extern bool _cpp_stack_include (cpp_reader *, const char *, int,
 				enum include_type, location_t);
 extern int _cpp_compare_file_date (cpp_reader *, const char *, int);