PR preprocessor/60723 - missing system-ness marks for macro tokens

When a system macro is expanded in a non-system file during
out-of-line preprocessing, it can happen that the preprocessor forgets
to emit line markers to express the system-ness status of tokens that
come after the expansion of the macro.

That can lead to situations where the entire non-system file can be
considered as being a system file and thus have its warnings be
discarded during the compilation of the resulting preprocessed file.

My understanding is that this is due to the preprocessor not
systematically detecting (and reporting) the change in system-ness of
tokens.

And this is what this patch does.  Each time the system-ness of a
given token is different from the previous token that was emitted by
the preprocessor, it emits a line marker for the sole purpose of
marking the new system-ness of the subsequent tokens to come.

Bootstrapped and tested on x86_64-unknown-linux-gnu against trunk.

gcc/c-family/ChangeLog:
	* c-ppoutput.c (struct print::prev_was_system_token): New data
	member.
	(init_pp_output): Initialize it.
	(maybe_print_line_1, maybe_print_line, print_line_1, print_line)
	(do_line_change): Return a flag saying if a line marker was
	emitted or not.
	(scan_translation_unit): Detect if the system-ness of the token we
	are about to emit is different from the one of the previously
	emitted token.  If so, emit a line marker.  Avoid emitting
	useless adjacent line markers.
	(scan_translation_unit_directives_only): Adjust.

gcc/testsuite/ChangeLog:
	* gcc.dg/cpp/syshdr{4,5}.{c,h}: New test files.

Signed-off-by: Dodji Seketeli <dodji@redhat.com>

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@212194 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 52 insertions, 24 deletions

diff --git a/gcc/c-family/c-ppoutput.c b/gcc/c-family/c-ppoutput.c
index f3b5fa4487d..618e1c94b6c 100644
--- a/gcc/c-family/c-ppoutput.c
+++ b/gcc/c-family/c-ppoutput.c
@@ -36,6 +36,8 @@ static struct
   unsigned char printed;	/* Nonzero if something output at line.  */
   bool first_time;		/* pp_file_change hasn't been called yet.  */
   const char *src_file;		/* Current source file.  */
+  bool prev_was_system_token;	/* True if the previous token was a
+				   system token.*/
 } print;
 
 /* Defined and undefined macros being queued for output with -dU at
@@ -58,11 +60,11 @@ static void account_for_newlines (const unsigned char *, size_t);
 static int dump_macro (cpp_reader *, cpp_hashnode *, void *);
 static void dump_queued_macros (cpp_reader *);
 
-static void print_line_1 (source_location, const char*, FILE *);
-static void print_line (source_location, const char *);
-static void maybe_print_line_1 (source_location, FILE *);
-static void maybe_print_line (source_location);
-static void do_line_change (cpp_reader *, const cpp_token *,
+static bool print_line_1 (source_location, const char*, FILE *);
+static bool print_line (source_location, const char *);
+static bool maybe_print_line_1 (source_location, FILE *);
+static bool maybe_print_line (source_location);
+static bool do_line_change (cpp_reader *, const cpp_token *,
 			    source_location, int);
 
 /* Callback routines for the parser.   Most of these are active only
@@ -156,6 +158,7 @@ init_pp_output (FILE *out_stream)
   print.outf = out_stream;
   print.first_time = 1;
   print.src_file = "";
+  print.prev_was_system_token = false;
 }
 
 /* Writes out the preprocessed file, handling spacing and paste
@@ -168,6 +171,7 @@ scan_translation_unit (cpp_reader *pfile)
     = cpp_get_options (parse_in)->lang != CLK_ASM
       && !flag_no_line_commands;
   bool in_pragma = false;
+  bool line_marker_emitted = false;
 
   print.source = NULL;
   for (;;)
@@ -200,7 +204,7 @@ scan_translation_unit (cpp_reader *pfile)
 	      && do_line_adjustments
 	      && !in_pragma)
 	    {
-	      do_line_change (pfile, token, loc, false);
+	      line_marker_emitted = do_line_change (pfile, token, loc, false);
 	      putc (' ', print.outf);
 	    }
 	  else if (print.source->flags & PREV_WHITE
@@ -216,7 +220,7 @@ scan_translation_unit (cpp_reader *pfile)
 	  if (src_line != print.src_line
 	      && do_line_adjustments
 	      && !in_pragma)
-	    do_line_change (pfile, token, loc, false);
+	    line_marker_emitted = do_line_change (pfile, token, loc, false);
 	  putc (' ', print.outf);
 	}
 
@@ -228,7 +232,7 @@ scan_translation_unit (cpp_reader *pfile)
 	  const char *space;
 	  const char *name;
 
-	  maybe_print_line (token->src_loc);
+	  line_marker_emitted = maybe_print_line (token->src_loc);
 	  fputs ("#pragma ", print.outf);
 	  c_pp_lookup_pragma (token->val.pragma, &space, &name);
 	  if (space)
@@ -248,9 +252,18 @@ scan_translation_unit (cpp_reader *pfile)
 	  if (cpp_get_options (parse_in)->debug)
 	      linemap_dump_location (line_table, token->src_loc,
 				     print.outf);
+
+	  if (!line_marker_emitted
+	      && print.prev_was_system_token != !!in_system_header_at(loc))
+	    /* The system-ness of this token is different from the one
+	       of the previous token.  Let's emit a line change to
+	       mark the new system-ness before we emit the token.  */
+	    line_marker_emitted = do_line_change (pfile, token, loc, false);
 	  cpp_output_token (token, print.outf);
+	  line_marker_emitted = false;
 	}
 
+      print.prev_was_system_token = !!in_system_header_at(loc);
       /* CPP_COMMENT tokens and raw-string literal tokens can
 	 have embedded new-line characters.  Rather than enumerating
 	 all the possible token types just check if token uses
@@ -275,7 +288,7 @@ scan_translation_unit_directives_only (cpp_reader *pfile)
   struct _cpp_dir_only_callbacks cb;
 
   cb.print_lines = print_lines_directives_only;
-  cb.maybe_print_line = maybe_print_line;
+  cb.maybe_print_line = (void (*) (source_location)) maybe_print_line;
 
   _cpp_preprocess_dir_only (pfile, &cb);
 }
@@ -306,11 +319,13 @@ scan_translation_unit_trad (cpp_reader *pfile)
 
 /* If the token read on logical line LINE needs to be output on a
    different line to the current one, output the required newlines or
-   a line marker, and return 1.  Otherwise return 0.  */
+   a line marker.  If a line marker was emitted, return TRUE otherwise
+   return FALSE.  */
 
-static void
+static bool
 maybe_print_line_1 (source_location src_loc, FILE *stream)
 {
+  bool emitted_line_marker = false;
   int src_line = LOCATION_LINE (src_loc);
   const char *src_file = LOCATION_FILE (src_loc);
 
@@ -334,29 +349,34 @@ maybe_print_line_1 (source_location src_loc, FILE *stream)
 	}
     }
   else
-    print_line_1 (src_loc, "", stream);
+    emitted_line_marker = print_line_1 (src_loc, "", stream);
 
+  return emitted_line_marker;
 }
 
 /* If the token read on logical line LINE needs to be output on a
    different line to the current one, output the required newlines or
-   a line marker, and return 1.  Otherwise return 0.  */
+   a line marker.  If a line marker was emitted, return TRUE otherwise
+   return FALSE.  */
 
-static void
+static bool
 maybe_print_line (source_location src_loc)
 {
   if (cpp_get_options (parse_in)->debug)
     linemap_dump_location (line_table, src_loc,
 			   print.outf);
-  maybe_print_line_1 (src_loc, print.outf);
+  return maybe_print_line_1 (src_loc, print.outf);
 }
 
 /* Output a line marker for logical line LINE.  Special flags are "1"
-   or "2" indicating entering or leaving a file.  */
+   or "2" indicating entering or leaving a file.  If the line marker
+   was effectively emitted, return TRUE otherwise return FALSE.  */
 
-static void
+static bool
 print_line_1 (source_location src_loc, const char *special_flags, FILE *stream)
 {
+  bool emitted_line_marker = false;
+
   /* End any previous line of text.  */
   if (print.printed)
     putc ('\n', stream);
@@ -391,33 +411,39 @@ print_line_1 (source_location src_loc, const char *special_flags, FILE *stream)
 	fputs (" 3", stream);
 
       putc ('\n', stream);
+      emitted_line_marker = true;
     }
+
+  return emitted_line_marker;
 }
 
 /* Output a line marker for logical line LINE.  Special flags are "1"
-   or "2" indicating entering or leaving a file.  */
+   or "2" indicating entering or leaving a file.  Return TRUE if a
+   line marker was effectively emitted, FALSE otherwise.  */
 
-static void
+static bool
 print_line (source_location src_loc, const char *special_flags)
 {
     if (cpp_get_options (parse_in)->debug)
       linemap_dump_location (line_table, src_loc,
 			     print.outf);
-    print_line_1 (src_loc, special_flags, print.outf);
+    return print_line_1 (src_loc, special_flags, print.outf);
 }
 
-/* Helper function for cb_line_change and scan_translation_unit.  */
-static void
+/* Helper function for cb_line_change and scan_translation_unit.
+   Return TRUE if a line marker is emitted, FALSE otherwise.  */
+static bool
 do_line_change (cpp_reader *pfile, const cpp_token *token,
 		source_location src_loc, int parsing_args)
 {
+  bool emitted_line_marker = false;
   if (define_queue || undef_queue)
     dump_queued_macros (pfile);
 
   if (token->type == CPP_EOF || parsing_args)
-    return;
+    return false;
 
-  maybe_print_line (src_loc);
+  emitted_line_marker = maybe_print_line (src_loc);
   print.prev = 0;
   print.source = 0;
 
@@ -434,6 +460,8 @@ do_line_change (cpp_reader *pfile, const cpp_token *token,
       while (-- spaces >= 0)
 	putc (' ', print.outf);
     }
+
+  return emitted_line_marker;
 }
 
 /* Called when a line of output is started.  TOKEN is the first token