Initial implementation of archer's expression parser plug-in.

12 files changed, 1249 insertions, 2 deletions

diff --git a/archer-expr-plugin/COPYING3 b/archer-expr-plugin/COPYING3
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+                    GNU GENERAL PUBLIC LICENSE
+                       Version 3, 29 June 2007
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+ALL NECESSARY SERVICING, REPAIR OR CORRECTION.
+
+  16. Limitation of Liability.
+
+  IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
+WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR CONVEYS
+THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY
+GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE
+USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF
+DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD
+PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS),
+EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF
+SUCH DAMAGES.
+
+  17. Interpretation of Sections 15 and 16.
+
+  If the disclaimer of warranty and limitation of liability provided
+above cannot be given local legal effect according to their terms,
+reviewing courts shall apply local law that most closely approximates
+an absolute waiver of all civil liability in connection with the
+Program, unless a warranty or assumption of liability accompanies a
+copy of the Program in return for a fee.
+
+                     END OF TERMS AND CONDITIONS
+
+            How to Apply These Terms to Your New Programs
+
+  If you develop a new program, and you want it to be of the greatest
+possible use to the public, the best way to achieve this is to make it
+free software which everyone can redistribute and change under these terms.
+
+  To do so, attach the following notices to the program.  It is safest
+to attach them to the start of each source file to most effectively
+state the exclusion of warranty; and each file should have at least
+the "copyright" line and a pointer to where the full notice is found.
+
+    <one line to give the program's name and a brief idea of what it does.>
+    Copyright (C) <year>  <name of author>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+Also add information on how to contact you by electronic and paper mail.
+
+  If the program does terminal interaction, make it output a short
+notice like this when it starts in an interactive mode:
+
+    <program>  Copyright (C) <year>  <name of author>
+    This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
+    This is free software, and you are welcome to redistribute it
+    under certain conditions; type `show c' for details.
+
+The hypothetical commands `show w' and `show c' should show the appropriate
+parts of the General Public License.  Of course, your program's commands
+might be different; for a GUI interface, you would use an "about box".
+
+  You should also get your employer (if you work as a programmer) or school,
+if any, to sign a "copyright disclaimer" for the program, if necessary.
+For more information on this, and how to apply and follow the GNU GPL, see
+<http://www.gnu.org/licenses/>.
+
+  The GNU General Public License does not permit incorporating your program
+into proprietary programs.  If your program is a subroutine library, you
+may consider it more useful to permit linking proprietary applications with
+the library.  If this is what you want to do, use the GNU Lesser General
+Public License instead of this License.  But first, please read
+<http://www.gnu.org/philosophy/why-not-lgpl.html>.
diff --git a/archer-expr-plugin/Makefile b/archer-expr-plugin/Makefile
new file mode 100644
index 00000000000..cd11403e706
--- /dev/null
+++ b/archer-expr-plugin/Makefile
@@ -0,0 +1,63 @@
+# Makefile for GNU Compiler Collection C and C++ expression parser
+# plug-ins.
+# Copyright (C) 2011 Red Hat, Inc.
+# Written by Keith Seitz <keiths@redhat.com>
+#
+# This file is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+# 
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+# 
+# You should have received a copy of the GNU General Public License
+# along with this program; see the file COPYING3.  If not see
+# <http://www.gnu.org/licenses/>.
+
+C_PLUGIN_NAME=cexpr
+CP_PLUGIN_NAME=cpexpr
+
+GCC=gcc
+PLUGIN_SOURCE_FILES= gccexpr.c
+C_PLUGIN_OBJECT_FILES= cexpr.o
+CP_PLUGIN_OBJECT_FILES= cpexpr.o
+GCCPLUGINS_DIR:= $(shell $(GCC) -print-file-name=plugin)
+CFLAGS+= -I$(GCCPLUGINS_DIR)/include -fPIC -g -c
+
+all: c-common.h.stamp $(C_PLUGIN_NAME).so $(CP_PLUGIN_NAME).so
+
+# This is a hack.  The source file gcc/c-family/c-common.h is not installed
+# into $(GCCPLUGINS_DIR)/include/c-family.  It is instead installed into
+# $(GCCPLUGINS_DIR)/include.  Normally not a problem, except that
+# cp-tree.h #includes "c-family/c-common.h".  So the build will fail if this
+# file is not in the right place.  To work around this temporarily, the
+# build will check if this file is absent and copy it into the right place.
+c-common.h.stamp: $(GCCPLUGINS_DIR)/include/c-common.h
+	@test -f $(GCCPLUGINS_DIR)/include/c-family/c-common.h \
+		|| (cp $^ $(GCCPLUGINS_DIR)/include/c-family/c-common.h \
+		    && echo "WARNING: c-family/c-common.h missing: copying from $(GCCPLUGINS_DIR)/include")
+	touch c-common.h.stamp
+
+$(C_PLUGIN_NAME).so: $(C_PLUGIN_OBJECT_FILES)
+	$(GCC) -shared $^ -o $@
+
+$(CP_PLUGIN_NAME).so: $(CP_PLUGIN_OBJECT_FILES)
+	$(GCC) -shared $^ -o $@
+
+install: $(C_PLUGIN_NAME).so $(CP_PLUGIN_NAME).so
+	cp $^ $(GCCPLUGINS_DIR)
+
+$(C_PLUGIN_OBJECT_FILES): $(PLUGIN_SOURCE_FILES)
+	$(GCC) $(CFLAGS) $^ -o $@
+
+$(CP_PLUGIN_OBJECT_FILES): $(PLUGIN_SOURCE_FILES)
+	$(GCC) $(CFLAGS) -DCPLUS $^ -o $@
+
+clean:
+	rm -f $(C_PLUGIN_OBJECT_FILES) $(CP_PLUGIN_OBJECT_FILES) \
+		$(C_PLUGIN_NAME).so $(CP_PLUGIN_NAME).so c-common.h.stamp *~
+
+
diff --git a/archer-expr-plugin/README b/archer-expr-plugin/README
new file mode 100644
index 00000000000..1b32b499f51
--- /dev/null
+++ b/archer-expr-plugin/README
@@ -0,0 +1,38 @@
+This directory contains sources for the gcc/g++ archer plug-in.
+
+This plug-in (actually two of them -- one for C and one for C++) was
+created in order to experiment/play with (re)using the compiler's parsers
+for expression parsing in gdb.  The source code here builds on
+GNU/Linux systems (tested only on Fedora 12+), and it is not yet integrated
+into the gcc build infrastructure.
+
+You will have to build the plug-in(s) by hand. To do so, build and install
+gcc and g++ in the usual way.  Add the resulting compiler to your PATH,
+and type "make all" in this directory (which resides in the source
+tree for now).  This should build the gcc and g++ expression
+parser plug-ins. You may also type "make install" to have the plug-ins
+automatically installed into your new compiler installation.
+
+You can then play with the plug-in by passing -fplugin=cexpr or
+-fplugin=cpexpr on the command-line.  Required arguments are
+-fplugin-cexpr-location=FILENAME:LINE and -fplugin-cexpr-expr=EXPRESSION.
+-c and -o /dev/null flags are recommended.  [Substitute "cpexpr" for "cexpr"
+in above if you are evaluating a C++ expression with g++.]
+
+The plug-ins currently uses debug_tree to output the result, and it outputs
+a little blurb about how the expression was evaluated (at the given location
+or at the end of the file) and how long it took to get from (the end of)
+plug-in initialization to output of the resultant tree.
+
+A complete example of how to use the plug-in (C++):
+
+$ g++ -c -o /devl/null -fplugin=cpexpr \
+      -fplugin-arg-cpexpr-location=foo.cc:21 \
+      -fplugin-arg-cpexpr-expr="1 + local_variable" \
+      [any required flags to compile source code] \
+      foo.cc
+
+The example here assumes that the plug-in(s) were installed.  You may
+also specify the path to the plug-in with the -fplugin flag, e.g.,
+-fplugin=/path/to/cpexpr.
+
diff --git a/archer-expr-plugin/gccexpr.c b/archer-expr-plugin/gccexpr.c
new file mode 100644
index 00000000000..c51bb424ae7
--- /dev/null
+++ b/archer-expr-plugin/gccexpr.c
@@ -0,0 +1,395 @@
+/* gccexpr.c - A C/C++ compiler plug-in to parse expressions
+   Copyright (C) 2011 Red Hat, Inc.
+   Written by Keith Seitz  <keiths@redhat.com>
+
+   This file is free software; you can redistribute it and/or modify it
+   under the terms of the GNU General Public License as published by the Free
+   Software Foundation; either version 3, or (at your option) any later
+   version.
+
+   The program is distributed in the hope that it will be useful, but
+   WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+   or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+   for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; see the file COPYING3.  If not see
+   <http://www.gnu.org/licenses/>.  */
+
+/* This source file actually is used to build two GCC plug-ins, one
+   for C code (which is a GCC plug-in) and one for C++ code (which is
+   a G++ plug-in).  The accompanying Makefile will build both of these
+   plug-ins, named "cexpr" and "cpexpr".  Enable  either plug-in by passing
+   its name as the value to "-fplugin" argument.  Then pass a location
+   (FILENAME:NUMBER) via "-fplugin-arg-c[p]expr-location" and
+   an expression to evaluate via "-fplugin-arg-c[p]expr-expr".
+
+   NOTE: The location is defined as the end (or sometimes middle)
+   of the line. To evaluate an expression before the given line is
+   compiled, you must specify the previous line.
+
+   How to call this plug-in (because I always forget):
+ 
+   In objdir for the file:
+   $ g{++,cc} -c -o /dev/null -fplugin=/path/to/c[p]expr	\
+     -fplugin-arg-c[p]expr-location="<sourcefile>.<line>"	\
+     -fplugin-arg-c[p]expr-expr="<expression>"			\
+     [all other build flags, defines, etc] filename
+
+   If you install the plug-in into your GCC installdir, you can omit
+   the "/path/to" bits and simply specify "-fplugin=c[p]expr".
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <errno.h>
+
+#include "gcc-plugin.h"
+#include "plugin-version.h"
+#include "cpplib.h"
+#include "coretypes.h"
+#include "toplev.h"
+#include "input.h"
+#include "c-pragma.h"
+
+#ifdef CPLUS
+#include "cp/cp-tree.h"
+#include "c-pretty-print.h"
+extern tree cp_parser_evaluate_expression (const char *);
+#else
+#include "tree.h"
+#include "c-pretty-print.h"
+#include "diagnostic.h"
+extern tree c_parser_evaluate_expression (const char *);
+#endif
+
+#define DEBUGGING 0
+
+#if DEBUGGING
+#define DEBUG(FMT, ARGS...)			\
+  do						\
+    {						\
+      printf ("EXPRPLUGIN " FMT "\n", ##ARGS);	\
+    }						\
+  while (0)
+#else
+#define DEBUG(FMT, ARGS...) /* nadda */
+#endif
+
+/* Freedom!  */
+int plugin_is_GPL_compatible;
+
+/* Plug-in information  */
+static struct plugin_info gccexpr_info =
+  { "0.01", "expression evaluaton plug-in" };
+
+#define PLUGIN_ARGV_LOCATION "location"
+#define PLUGIN_ARGV_EXPRESSION "expr"
+
+/* User data for the PLUGIN_PARSE_LINE callback.  */
+
+struct gccexpr_data
+{
+  /* The location at which to halt parsing.
+
+     Note that this location must be the line previous
+     to where we want expression parsing done.  GDB will have
+     to figure this out for us.  */
+  expanded_location loc;
+
+  /* The expression to evaluate when we stop.  */
+  char *expr;
+
+  /* Set to TRUE if this expression has already failed evaluation
+     and should be attempted at exit.  */
+  bool at_exit;
+
+  /* Timer variable for start of run.  */
+  long start_time;
+};
+
+/* Outputs the given TREE in a meaningful way to the terminal.  */
+
+static void
+output_tree (tree tree)
+{
+  /* For now, simply call debug_tree.  */
+  debug_tree (tree);  
+}
+
+/* A wrapper function to call the correct version of the
+   parser's expression evaluator.  */
+
+static tree
+evaluate_expression (const char *expr)
+{
+#ifdef CPLUS
+  return cp_parser_evaluate_expression (expr);
+#else
+  return c_parser_evaluate_expression (expr);
+#endif
+}
+
+/* Print out time statistics.  */
+
+static void
+print_time_usage (const char *str, struct gccexpr_data *data)
+{
+  long now = get_run_time ();
+  print_time (str, now - data->start_time);
+}
+
+/* Print a usage message.  */
+
+static void
+print_usage (struct plugin_name_args *info)
+{
+  fprintf (stderr,
+	   "%s: usage: -fplugin=%s -fplugin-arg-%s-%s=<file>:<line> "
+	   "-fplugin-arg-%s-%s=<expression>\n", info->base_name,
+	   info->base_name,
+	   info->base_name, PLUGIN_ARGV_LOCATION,
+	   info->base_name, PLUGIN_ARGV_EXPRESSION);
+}
+
+/* PLUGIN_PARSE_LINE callback function.  */
+
+static void
+gccexpr_parse_line_callback (void *gcc_data, void *user_data)
+{
+  struct gccexpr_data *data = (struct gccexpr_data *) user_data;
+  expanded_location loc = expand_location (input_location);
+
+  DEBUG ("parse_line_cb: %s:%d", loc.file, loc.line);
+
+  if (loc.file && !data->at_exit)
+    {
+      /* FIXME: lbasename? Could this be asking for trouble? */
+      if (strcmp (lbasename (loc.file), data->loc.file) == 0
+	  && loc.line >= data->loc.line)
+	{
+	  tree result;
+
+	  DEBUG ("evaluating expression %s", data->expr);
+
+	  /* Evaluate the expression.  */
+	  result = evaluate_expression (data->expr);
+
+	  /* If we see an error, mark this expression to try evaluation
+	     at exit.  */
+	  if (result != error_mark_node)
+	    {
+	      /* Print out the resulting tree.  */
+	      output_tree (result);
+	      print_time_usage ("evaluating in-line expression", data);
+	      exit (0);
+	    }
+	  else
+	    {
+	      DEBUG ("evaluation failed -- deferring");
+	      data->at_exit = true;
+	    }
+	}
+    }
+}
+
+/* This function is called just before GCC exits.  It is responsible
+   for freeing any resources used by this plugin.  */
+
+static void
+gccexpr_finish_callback (void *gcc_data, void *user_data)
+{
+  struct gccexpr_data *data = (struct gccexpr_data *) user_data;
+
+  DEBUG ("finish_callback");
+  if (data->at_exit)
+    {
+      tree result;
+
+      /* Try again.  */
+      result = evaluate_expression (data->expr);
+      if (result != error_mark_node)
+	{
+	  output_tree (result);
+	  print_time_usage ("evaluating expression at exit", data);
+	  exit (0);
+	}
+    }
+
+  print_time_usage ("evaluating failed expression", data);
+  free (data->expr);
+  free (data);
+}
+
+/* Nop pretty-printer to supress diagnostics.  */
+
+static void
+gccexpr_pretty_print (c_pretty_printer *pp, tree t)
+{
+  /* do nothing */
+}
+
+static void
+gccexpr_init_diagnostics (diagnostic_context *context)
+{
+  static c_pretty_printer nop_printer;
+  static bool initialized = false;
+  c_pretty_printer *pp = &nop_printer;
+
+  pp_construct (pp_base (pp), NULL, 0);
+  pp->offset_list               = 0;
+
+  pp->declaration               = gccexpr_pretty_print;
+  pp->declaration_specifiers    = gccexpr_pretty_print;
+  pp->declarator                = gccexpr_pretty_print;
+  pp->direct_declarator         = gccexpr_pretty_print;
+  pp->type_specifier_seq        = gccexpr_pretty_print;
+  pp->abstract_declarator       = gccexpr_pretty_print;
+  pp->direct_abstract_declarator = gccexpr_pretty_print;
+  pp->ptr_operator              = gccexpr_pretty_print;
+  pp->parameter_list            = gccexpr_pretty_print;
+  pp->type_id                   = gccexpr_pretty_print;
+  pp->simple_type_specifier     = gccexpr_pretty_print;
+  pp->function_specifier        = gccexpr_pretty_print;
+  pp->storage_class_specifier   = gccexpr_pretty_print;
+
+  pp->statement                 = gccexpr_pretty_print;
+
+  pp->constant                  = gccexpr_pretty_print;
+  pp->id_expression             = gccexpr_pretty_print;
+  pp->primary_expression        = gccexpr_pretty_print;
+  pp->postfix_expression        = gccexpr_pretty_print;
+  pp->unary_expression          = gccexpr_pretty_print;
+  pp->initializer               = gccexpr_pretty_print;
+  pp->multiplicative_expression = gccexpr_pretty_print;
+  pp->conditional_expression    = gccexpr_pretty_print;
+  pp->assignment_expression     = gccexpr_pretty_print;
+  pp->expression                = gccexpr_pretty_print;
+
+  context->printer = (pretty_printer *) pp;
+}
+
+/* Plug-in initialization function  */
+
+int
+plugin_init (struct plugin_name_args *plugin_info,
+	     struct plugin_gcc_version *version)
+{
+  int i, expr_event;
+  const char *p;
+  const char *location = NULL;
+  char *expression = NULL;
+  expanded_location eloc;
+  struct gccexpr_data *data;
+
+  if (!plugin_default_version_check (version, &gcc_version))
+    return 1;
+
+  DEBUG ("plugin_init");
+
+  /* We must have two parameters, the location and the expression.  */
+  if (plugin_info->argc != 2)
+    {
+      print_usage (plugin_info);
+      return 1;
+    }
+
+  /* Extract the evaluation location and expression from the arguments.  */
+  for (i = 0; i < plugin_info->argc; ++i)
+    {
+      if (strcmp (PLUGIN_ARGV_LOCATION, plugin_info->argv[i].key) == 0)
+	location = plugin_info->argv[i].value;
+      else if (strcmp (PLUGIN_ARGV_EXPRESSION, plugin_info->argv[i].key) == 0)
+	{
+	  /* The lexer requires that we end in a newline; so append it.  */
+	  expression = xmalloc (strlen (plugin_info->argv[i].value) + 3);
+	  strcpy (expression, plugin_info->argv[i].value);
+	  strcat (expression, "\n");
+	}
+      else
+	{
+	  fprintf (stderr, "%s: unknown argument key: \"%s\"\n",
+		   plugin_info->base_name, plugin_info->argv[i].key);
+	  print_usage (plugin_info);
+	  return 1;
+	}
+    }
+
+  /* If either LOCATION or EXPRESSION was not specified, issue an
+     error message and fail initialization.  */
+  if (location == NULL || expression == NULL)
+    {
+      fprintf (stderr, "%s: must specify both -fplugin-args-%s-%s and "
+	       "-fplugin-args-%s-%s\n", plugin_info->base_name,
+	       plugin_info->base_name, PLUGIN_ARGV_LOCATION,
+	       plugin_info->base_name, PLUGIN_ARGV_EXPRESSION);
+      return 1;
+    }
+
+  /* Parse the location information, which should be of the form
+     "FILENAME:LINE".  */
+  
+  p = location;
+  while (*p != ':' && *p != '\0')
+    ++p;
+
+  if (*p == '\0')
+    {
+      /* We ran to the end of the string without finding ':'.  */
+      fprintf (stderr, "%s: error in location, expected \"<file>:<line>\"\n",
+	       plugin_info->base_name);
+      return 1;
+    }
+
+  data = XNEW (struct gccexpr_data);
+  data->expr = expression;
+  data->at_exit = false;
+  eloc.file = strndup (location, p - location);
+  errno = 0;
+  eloc.line = strtoul (++p, (char **) NULL, 10);
+  if (errno != 0)
+    {
+      char buf[256];
+      fprintf (stderr, ":error converting line number: %s\n",
+	       plugin_info->base_name, strerror_r (errno, buf, sizeof (buf)));
+      return 1;
+
+    }
+  else if (eloc.line < 0)
+    {
+      fprintf (stderr, "%s: line number must be >= 0\n",
+	       plugin_info->base_name);
+      return 1;
+    }
+
+  DEBUG ("location: %s:%d\n", eloc.file, eloc.line);
+
+  data->loc = eloc;
+
+  /* Register our plugin info  */
+  register_callback (plugin_info->base_name, PLUGIN_INFO,
+		     (plugin_callback_func) NULL, &gccexpr_info);
+
+  /* Register a callback for the PLUGIN_PARSE_LINE event.  */
+  register_callback (plugin_info->base_name, PLUGIN_PARSE_LINE,
+		     gccexpr_parse_line_callback, data);
+
+  /* Register a finish event callback to handle any cleanup.  */
+  register_callback (plugin_info->base_name, PLUGIN_FINISH,
+		     gccexpr_finish_callback, data);
+
+  /* From here on out, we don't want diagnostic information (warnings
+     and errors) output to the terminal, so install a blank pretty
+     printer which effectively disables this.  */
+  /* NOTE: This does not seem sufficient... */
+  gccexpr_init_diagnostics (global_dc);
+
+#ifdef CPLUS
+  /* Defer all access checks, too.  */
+  push_deferring_access_checks (dk_no_check);
+#endif
+
+  /* Set the timer.  */
+  data->start_time = get_run_time ();
+  return 0;
+}
diff --git a/gcc/c-decl.c b/gcc/c-decl.c
index b438b066c83..ebc278876f6 100644
--- a/gcc/c-decl.c
+++ b/gcc/c-decl.c
@@ -558,6 +558,7 @@ add_stmt (tree t)
      recorded during statement expressions.  */
   append_to_statement_list_force (t, &cur_stmt_list);
 
+  invoke_plugin_callbacks (PLUGIN_PARSE_LINE, NULL);
   return t;
 }
 
diff --git a/gcc/c-parser.c b/gcc/c-parser.c
index 69ce2e50bef..9664aaf37fa 100644
--- a/gcc/c-parser.c
+++ b/gcc/c-parser.c
@@ -1186,6 +1186,46 @@ static void c_parser_objc_at_synthesize_declaration (c_parser *);
 static void c_parser_objc_at_dynamic_declaration (c_parser *);
 static bool c_parser_objc_diagnose_bad_element_prefix
   (c_parser *, struct c_declspecs *);
+static void c_parser_pragma_pch_preprocess (c_parser *);
+
+tree c_parser_evaluate_expression (const char *);
+
+tree
+c_parser_evaluate_expression (const char *expression)
+{
+  cpp_buffer *buf;
+  struct c_expr result;
+
+  /* Use local storage to begin.  If the first token is a pragma, parse it.
+     If it is #pragma GCC pch_preprocess, then this will load a PCH file
+     which will cause garbage collection.  */
+  c_parser tparser;
+
+  memset (&tparser, 0, sizeof tparser);
+  the_parser = &tparser;
+
+  /* Discard any previous input buffers.  */
+  cpp_pop_all_buffers (parse_in);
+
+  /* Tokenize the input expression.  */
+  buf = cpp_push_buffer (parse_in, (const unsigned char *) expression,
+			 strlen (expression), 0);
+ 
+  if (c_parser_peek_token (&tparser)->pragma_kind == PRAGMA_GCC_PCH_PREPROCESS)
+    c_parser_pragma_pch_preprocess (&tparser);
+
+  the_parser = ggc_alloc_c_parser ();
+  *the_parser = tparser;
+
+  /* Initialize EH, if we've been told to do so.  */
+  if (flag_exceptions)
+    using_eh_for_cleanups ();
+
+  /*c_parser_translation_unit (the_parser);*/
+  result = c_parser_expression (the_parser);
+  the_parser = NULL;
+  return result.value;
+}
 
 /* Parse a translation unit (C90 6.7, C99 6.9).
 
diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index 93c184845f9..0e25ae5028d 100644
--- a/gcc/cp/decl.c
+++ b/gcc/cp/decl.c
@@ -13297,6 +13297,7 @@ cxx_maybe_build_cleanup (tree decl)
 void
 finish_stmt (void)
 {
+  invoke_plugin_callbacks (PLUGIN_PARSE_LINE, NULL);
 }
 
 /* Return the FUNCTION_TYPE that corresponds to MEMFNTYPE, which can be a
diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index 510fcb11179..82d15bb7f9f 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -1830,7 +1830,7 @@ static tree cp_parser_assignment_expression
   (cp_parser *, bool, cp_id_kind *);
 static enum tree_code cp_parser_assignment_operator_opt
   (cp_parser *);
-static tree cp_parser_expression
+tree cp_parser_expression
   (cp_parser *, bool, cp_id_kind *);
 static tree cp_parser_constant_expression
   (cp_parser *, bool, bool *);
@@ -7176,7 +7176,7 @@ cp_parser_assignment_operator_opt (cp_parser* parser)
 
    Returns a representation of the expression.  */
 
-static tree
+tree
 cp_parser_expression (cp_parser* parser, bool cast_p, cp_id_kind * pidk)
 {
   tree expression = NULL_TREE;
@@ -25089,6 +25089,27 @@ cp_parser_omp_construct (cp_parser *parser, cp_token *pragma_tok)
 
 static GTY (()) cp_parser *the_parser;
 
+tree cp_parser_evaluate_expression (const char *);
+
+tree
+cp_parser_evaluate_expression (const char *expression)
+{
+  cpp_buffer *buf;
+  cp_parser *parser;
+  tree result;
+
+  /* Discard any previous inupt buffers.  */
+  cpp_pop_all_buffers (parse_in);
+
+  /* Tokenize the input expression.  */
+  buf = cpp_push_buffer (parse_in, expression, strlen (expression), 0);
+  parser = cp_parser_new ();
+
+  /* Evaluate it.  */
+  result = cp_parser_expression (parser, false, NULL);
+  return result;
+}
+
 
 /* Special handling for the first token or line in the file.  The first
    thing in the file might be #pragma GCC pch_preprocess, which loads a
diff --git a/gcc/plugin.c b/gcc/plugin.c
index c93daed055d..2d577f04b62 100644
--- a/gcc/plugin.c
+++ b/gcc/plugin.c
@@ -438,6 +438,7 @@ register_callback (const char *plugin_name,
       case PLUGIN_EARLY_GIMPLE_PASSES_START:
       case PLUGIN_EARLY_GIMPLE_PASSES_END:
       case PLUGIN_NEW_PASS:
+      case PLUGIN_PARSE_LINE:
         {
           struct callback_info *new_callback;
           if (!callback)
@@ -514,6 +515,7 @@ invoke_plugin_callbacks_full (int event, void *gcc_data)
       case PLUGIN_EARLY_GIMPLE_PASSES_START:
       case PLUGIN_EARLY_GIMPLE_PASSES_END:
       case PLUGIN_NEW_PASS:
+      case PLUGIN_PARSE_LINE:
         {
           /* Iterate over every callback registered with this event and
              call it.  */
diff --git a/gcc/plugin.def b/gcc/plugin.def
index 4a40c2cf79e..d69ed371cd8 100644
--- a/gcc/plugin.def
+++ b/gcc/plugin.def
@@ -89,6 +89,9 @@ DEFEVENT (PLUGIN_EARLY_GIMPLE_PASSES_END)
 /* Called when a pass is first instantiated.  */
 DEFEVENT (PLUGIN_NEW_PASS)
 
+/* Called after a an input line is parsed.  */
+DEFEVENT (PLUGIN_PARSE_LINE)
+
 /* After the hard-coded events above, plugins can dynamically allocate events
    at run time.
    PLUGIN_EVENT_FIRST_DYNAMIC only appears as last enum element.  */
diff --git a/libcpp/directives.c b/libcpp/directives.c
index 85a17b146c2..f43c052f952 100644
--- a/libcpp/directives.c
+++ b/libcpp/directives.c
@@ -2534,6 +2534,13 @@ _cpp_pop_buffer (cpp_reader *pfile)
     }
 }
 
+void
+cpp_pop_all_buffers (cpp_reader *pfile)
+{
+  while (CPP_BUFFER (pfile) != NULL)
+    _cpp_pop_buffer (pfile);
+}
+
 /* Enter all recognized directives in the hash table.  */
 void
 _cpp_init_directives (cpp_reader *pfile)
diff --git a/libcpp/include/cpplib.h b/libcpp/include/cpplib.h
index 8fa28819bed..c5d523566a8 100644
--- a/libcpp/include/cpplib.h
+++ b/libcpp/include/cpplib.h
@@ -763,6 +763,8 @@ extern void cpp_undef_all (cpp_reader *);
 
 extern cpp_buffer *cpp_push_buffer (cpp_reader *, const unsigned char *,
 				    size_t, int);
+extern void cpp_pop_all_buffers (cpp_reader *);
+
 extern int cpp_defined (cpp_reader *, const unsigned char *, int);
 
 /* A preprocessing number.  Code assumes that any unused high bits of