diff --git a/gcc/c-family/c-opts.c b/gcc/c-family/c-opts.c
index 3184539..6869d5c 100644
--- a/gcc/c-family/c-opts.c
+++ b/gcc/c-family/c-opts.c
@@ -628,6 +628,10 @@ c_common_handle_option (size_t scode, const char *arg, int value,
       cpp_opts->preprocessed = value;
       break;
 
+    case OPT_fdebug_cpp:
+      cpp_opts->debug = 1;
+      break;
+
     case OPT_ftrack_macro_expansion:
       if (value)
 	value = 2;
diff --git a/gcc/c-family/c-ppoutput.c b/gcc/c-family/c-ppoutput.c
index b4bc9ce..cb010c5 100644
--- a/gcc/c-family/c-ppoutput.c
+++ b/gcc/c-family/c-ppoutput.c
@@ -59,7 +59,9 @@ 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 *,
 			    source_location, int);
@@ -243,7 +245,12 @@ scan_translation_unit (cpp_reader *pfile)
 	  in_pragma = false;
 	}
       else
-	cpp_output_token (token, print.outf);
+	{
+	  if (cpp_get_options (parse_in)->debug)
+	      linemap_dump_location (line_table, token->src_loc,
+				     print.outf);
+	  cpp_output_token (token, print.outf);
+	}
 
       if (token->type == CPP_COMMENT)
 	account_for_newlines (token->val.str.text, token->val.str.len);
@@ -297,8 +304,9 @@ 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.  */
+
 static void
-maybe_print_line (source_location src_loc)
+maybe_print_line_1 (source_location src_loc, FILE *stream)
 {
   int src_line = LOCATION_LINE (src_loc);
   const char *src_file = LOCATION_FILE (src_loc);
@@ -306,7 +314,7 @@ maybe_print_line (source_location src_loc)
   /* End the previous line of text.  */
   if (print.printed)
     {
-      putc ('\n', print.outf);
+      putc ('\n', stream);
       print.src_line++;
       print.printed = 0;
     }
@@ -318,22 +326,37 @@ maybe_print_line (source_location src_loc)
     {
       while (src_line > print.src_line)
 	{
-	  putc ('\n', print.outf);
+	  putc ('\n', stream);
 	  print.src_line++;
 	}
     }
   else
-    print_line (src_loc, "");
+    print_line_1 (src_loc, "", stream);
+
+}
+
+/* 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.  */
+
+static void
+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);
 }
 
 /* Output a line marker for logical line LINE.  Special flags are "1"
    or "2" indicating entering or leaving a file.  */
+
 static void
-print_line (source_location src_loc, const char *special_flags)
+print_line_1 (source_location src_loc, const char *special_flags, FILE *stream)
 {
   /* End any previous line of text.  */
   if (print.printed)
-    putc ('\n', print.outf);
+    putc ('\n', stream);
   print.printed = 0;
 
   if (!flag_no_line_commands)
@@ -354,20 +377,32 @@ print_line (source_location src_loc, const char *special_flags)
 			    (const unsigned char *) file_path,
 			    to_file_len);
       *p = '\0';
-      fprintf (print.outf, "# %u \"%s\"%s",
+      fprintf (stream, "# %u \"%s\"%s",
 	       print.src_line == 0 ? 1 : print.src_line,
 	       to_file_quoted, special_flags);
 
       sysp = in_system_header_at (src_loc);
       if (sysp == 2)
-	fputs (" 3 4", print.outf);
+	fputs (" 3 4", stream);
       else if (sysp == 1)
-	fputs (" 3", print.outf);
+	fputs (" 3", stream);
 
-      putc ('\n', print.outf);
+      putc ('\n', stream);
     }
 }
 
+/* Output a line marker for logical line LINE.  Special flags are "1"
+   or "2" indicating entering or leaving a file.  */
+
+static void
+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);
+}
+
 /* Helper function for cb_line_change and scan_translation_unit.  */
 static void
 do_line_change (cpp_reader *pfile, const cpp_token *token,
diff --git a/gcc/c-family/c.opt b/gcc/c-family/c.opt
index 07a6b87..f9db8f1 100644
--- a/gcc/c-family/c.opt
+++ b/gcc/c-family/c.opt
@@ -739,6 +739,10 @@ fconstexpr-depth=
 C++ ObjC++ Joined RejectNegative UInteger Var(max_constexpr_depth) Init(512)
 -fconstexpr-depth=<number>	Specify maximum constexpr recursion depth
 
+fdebug-cpp
+C ObjC C++ ObjC++
+Emit debug annotations during preprocessing
+
 fdeduce-init-list
 C++ ObjC++ Var(flag_deduce_init_list) Init(1)
 -fno-deduce-init-list	disable deduction of std::initializer_list for a template type parameter from a brace-enclosed initializer-list
diff --git a/gcc/doc/cppopts.texi b/gcc/doc/cppopts.texi
index b225236..ef3a0b2 100644
--- a/gcc/doc/cppopts.texi
+++ b/gcc/doc/cppopts.texi
@@ -583,6 +583,19 @@ correct column numbers in warnings or errors, even if tabs appear on the
 line.  If the value is less than 1 or greater than 100, the option is
 ignored.  The default is 8.
 
+@item -fdebug-cpp
+@opindex fdebug-cpp
+This option is only useful for debugging GCC.  When used with
+@option{-E}, dumps debugging information about location maps.  Every
+token in the output is preceded by the dump of the map its location
+belongs to.  The dump of the map holding the location of a token would
+be:
+@quotation
+@{@samp{P}:@file{/file/path};@samp{F}:@file{/includer/path};@samp{L}:@var{line_num};@samp{C}:@var{col_num};@samp{S}:@var{system_header_p};@samp{M}:@var{map_address};@samp{E}:@var{macro_expansion_p},@samp{loc}:@var{location}@}
+@end quotation
+
+When used without @option{-E}, this option has no effect.
+
 @item -ftrack-macro-expansion@r{[}=@var{level}@r{]}
 @opindex ftrack-macro-expansion
 Track locations of tokens across macro expansions. This allows the
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 7e1b7c2..fedcf84 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -428,7 +428,7 @@ Objective-C and Objective-C++ Dialects}.
 -iwithprefixbefore @var{dir}  -isystem @var{dir} @gol
 -imultilib @var{dir} -isysroot @var{dir} @gol
 -M  -MM  -MF  -MG  -MP  -MQ  -MT  -nostdinc  @gol
--P -ftrack-macro-expansion -fworking-directory @gol
+-P  -fdebug-cpp -ftrack-macro-expansion -fworking-directory @gol
 -remap -trigraphs  -undef  -U@var{macro}  @gol
 -Wp,@var{option} -Xpreprocessor @var{option}}
 
diff --git a/libcpp/include/cpplib.h b/libcpp/include/cpplib.h
index 3e01c11..825bf2f 100644
--- a/libcpp/include/cpplib.h
+++ b/libcpp/include/cpplib.h
@@ -392,6 +392,10 @@ struct cpp_options
   /* Nonzero means we're looking at already preprocessed code, so don't
      bother trying to do macro expansion and whatnot.  */
   unsigned char preprocessed;
+  
+  /* Nonzero means we are going to emit debugging logs during
+     preprocessing.  */
+  unsigned char debug;
 
   /* Nonzero means we are tracking locations of tokens involved in
      macro expansion. 1 Means we track the location in degraded mode
diff --git a/libcpp/include/line-map.h b/libcpp/include/line-map.h
index 5b7ee9d..81fe6c9 100644
--- a/libcpp/include/line-map.h
+++ b/libcpp/include/line-map.h
@@ -800,4 +800,8 @@ expanded_location linemap_expand_location_full (struct line_maps *,
 						source_location loc,
 						enum location_resolution_kind lrk);
 
+/* Dump debugging information about source location LOC into the file
+   stream STREAM. SET is the line map set LOC comes from.  */
+void linemap_dump_location (struct line_maps *, source_location, FILE *);
+
 #endif /* !LIBCPP_LINE_MAP_H  */
diff --git a/libcpp/line-map.c b/libcpp/line-map.c
index 959566c..fbd88da 100644
--- a/libcpp/line-map.c
+++ b/libcpp/line-map.c
@@ -955,3 +955,41 @@ linemap_expand_location_full (struct line_maps *set,
   xloc = linemap_expand_location (map, loc);
   return xloc;
 }
+
+/* Dump debugging information about source location LOC into the file
+   stream STREAM. SET is the line map set LOC comes from.  */
+
+void
+linemap_dump_location (struct line_maps *set,
+		       source_location loc,
+		       FILE *stream)
+{
+  const struct line_map *map;
+  source_location location;
+  const char *path, *from;
+  int l,c,s,e;
+
+  if (loc == 0)
+    return;
+
+  location =
+    linemap_macro_loc_to_def_point (set, loc, &map, true);
+  path = LINEMAP_FILE (map);
+
+  l = SOURCE_LINE (map, location);
+  c = SOURCE_COLUMN (map, location);
+  s = LINEMAP_SYSP (map) != 0;
+  e = location != loc;
+
+  if (e)
+    from = "N/A";
+  else
+    from = (INCLUDED_FROM (set, map))
+      ? LINEMAP_FILE (INCLUDED_FROM (set, map))
+      : "<NULL>";
+
+  /* P: path, L: line, C: column, S: in-system-header, M: map address,
+     E: macro expansion?.   */
+  fprintf (stream, "{P:%s;F:%s;L:%d;C:%d;S:%d;M:%p;E:%d,LOC:%d}",
+	   path, from, l, c, s, (void*)map, e, loc);
+}
