diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index f6d1231ccc..1b95736db7 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,31 @@
+2002-05-17  Jim Blandy  <jimb@redhat.com>
+
+	Expand preprocessor macros in C expressions.
+	* c-lang.h: #include "macroexp.h", for macro_lookup_ftype.
+	(scan_macro_expansion, scanning_macro_expansion,
+	finished_macro_expansion): New function declarations.
+	(expression_macro_lookup_func, expression_macro_lookup_baton): New
+	variable declarations.
+	* parser-defs.h (expression_context_pc): New declaration.
+	* parse.c (expression_context_pc): New variable.
+	(parse_exp_1): Set expression_context_pc, as well as
+	expression_context_block.
+	* c-exp.y (yylex): If we're not already reading the result of a
+	macro expansion, try to macro-expand the next token.  When we're
+	done scanning a macro expansion, switch back to the mainline text.
+	Commas and `if's in a macro's expansion don't terminate the input.
+	* c-lang.c: #include "macroscope.h" and "gdb_assert.h".
+	(macro_original_text, macro_expanded_text,
+	expression_macro_lookup_func, expression_macro_lookup_baton): New
+	variables.
+	(scan_macro_expansion, scanning_macro_expansion,
+	finished_macro_expansion, scan_macro_cleanup, null_macro_lookup,
+	c_preprocess_and_parse): New functions.
+	(c_language_defn, cplus_language_defn, asm_language_defn): Call
+	c_preprocess_and_parse, instead of c_parse.
+	* Makefile.in (c_lang_h): Note that this #includes macroexp.h.
+	(c-lang.o): Note dependency on macroscope.h and gdb_assert.h.
+
 Fri May 17 14:26:19 2002  J"orn Rennecke <joern.rennecke@superh.com>
 
 	* sh-tdep.c (gdb_print_insn_sh64): Delete.
diff --git a/gdb/Makefile.in b/gdb/Makefile.in
index 37abd9f1e8..abe4d06a56 100644
--- a/gdb/Makefile.in
+++ b/gdb/Makefile.in
@@ -600,7 +600,7 @@ bcache_h =	bcache.h
 builtin_regs_h = builtin-regs.h
 breakpoint_h =	breakpoint.h $(frame_h) $(value_h)
 buildsym_h =	buildsym.h
-c_lang_h =	c-lang.h $(value_h)
+c_lang_h =	c-lang.h $(value_h) $(macroexp_h)
 call_cmds_h =	call-cmds.h
 cli_cmds_h =	$(srcdir)/cli/cli-cmds.h
 cli_decode_h =	$(srcdir)/cli/cli-decode.h $(command_h)
@@ -1318,7 +1318,8 @@ builtin-regs.o: builtin-regs.c $(defs.h) $(builtin_regs_h) $(gdbtypes_h) \
 	$(gdb_string_h) $(value_h) $(frame_h)
 
 c-lang.o: c-lang.c $(c_lang_h) $(defs_h) $(expression_h) $(gdbtypes_h) \
-	$(language_h) $(parser_defs_h) $(symtab_h)
+	$(language_h) $(parser_defs_h) $(symtab_h) $(macroscope_h) \
+	gdb_assert.h
 
 c-typeprint.o: c-typeprint.c $(c_lang_h) $(defs_h) $(expression_h) \
 	$(gdbcmd_h) $(gdbcore_h) $(gdbtypes_h) $(language_h) $(symtab_h) \
diff --git a/gdb/c-exp.y b/gdb/c-exp.y
index a15a4456bc..f555518ea0 100644
--- a/gdb/c-exp.y
+++ b/gdb/c-exp.y
@@ -1246,6 +1246,17 @@ yylex ()
    
  retry:
 
+  /* Check if this is a macro invocation that we need to expand.  */
+  if (! scanning_macro_expansion ())
+    {
+      char *expanded = macro_expand_next (&lexptr,
+                                          expression_macro_lookup_func,
+                                          expression_macro_lookup_baton);
+
+      if (expanded)
+        scan_macro_expansion (expanded);
+    }
+
   prev_lexptr = lexptr;
   unquoted_expr = 1;
 
@@ -1271,7 +1282,17 @@ yylex ()
   switch (c = *tokstart)
     {
     case 0:
-      return 0;
+      /* If we were just scanning the result of a macro expansion,
+         then we need to resume scanning the original text.
+         Otherwise, we were already scanning the original text, and
+         we're really done.  */
+      if (scanning_macro_expansion ())
+        {
+          finished_macro_expansion ();
+          goto retry;
+        }
+      else
+        return 0;
 
     case ' ':
     case '\t':
@@ -1324,7 +1345,9 @@ yylex ()
       return c;
 
     case ',':
-      if (comma_terminates && paren_depth == 0)
+      if (comma_terminates
+          && paren_depth == 0
+          && ! scanning_macro_expansion ())
 	return 0;
       lexptr++;
       return c;
@@ -1503,9 +1526,13 @@ yylex ()
       c = tokstart[++namelen];
     }
 
-  /* The token "if" terminates the expression and is NOT 
-     removed from the input stream.  */
-  if (namelen == 2 && tokstart[0] == 'i' && tokstart[1] == 'f')
+  /* The token "if" terminates the expression and is NOT removed from
+     the input stream.  It doesn't count if it appears in the
+     expansion of a macro.  */
+  if (namelen == 2
+      && tokstart[0] == 'i'
+      && tokstart[1] == 'f'
+      && ! scanning_macro_expansion ())
     {
       return 0;
     }
diff --git a/gdb/c-lang.c b/gdb/c-lang.c
index f98548a63a..09a2e6a968 100644
--- a/gdb/c-lang.c
+++ b/gdb/c-lang.c
@@ -27,6 +27,8 @@
 #include "language.h"
 #include "c-lang.h"
 #include "valprint.h"
+#include "macroscope.h"
+#include "gdb_assert.h"
 
 extern void _initialize_c_language (void);
 static void c_emit_char (int c, struct ui_file * stream, int quoter);
@@ -371,7 +373,128 @@ c_create_fundamental_type (struct objfile *objfile, int typeid)
   return (type);
 }
 
+/* Preprocessing and parsing C and C++ expressions.  */
 
+
+/* When we find that lexptr (the global var defined in parse.c) is
+   pointing at a macro invocation, we expand the invocation, and call
+   scan_macro_expansion to save the old lexptr here and point lexptr
+   into the expanded text.  When we reach the end of that, we call
+   end_macro_expansion to pop back to the value we saved here.  The
+   macro expansion code promises to return only fully-expanded text,
+   so we don't need to "push" more than one level.
+
+   This is disgusting, of course.  It would be cleaner to do all macro
+   expansion beforehand, and then hand that to lexptr.  But we don't
+   really know where the expression ends.  Remember, in a command like
+
+     (gdb) break *ADDRESS if CONDITION
+
+   we evaluate ADDRESS in the scope of the current frame, but we
+   evaluate CONDITION in the scope of the breakpoint's location.  So
+   it's simply wrong to try to macro-expand the whole thing at once.  */
+static char *macro_original_text;
+static char *macro_expanded_text;
+
+
+void
+scan_macro_expansion (char *expansion)
+{
+  /* We'd better not be trying to push the stack twice.  */
+  gdb_assert (! macro_original_text);
+  gdb_assert (! macro_expanded_text);
+
+  /* Save the old lexptr value, so we can return to it when we're done
+     parsing the expanded text.  */
+  macro_original_text = lexptr;
+  lexptr = expansion;
+
+  /* Save the expanded text, so we can free it when we're finished.  */
+  macro_expanded_text = expansion;
+}
+
+
+int
+scanning_macro_expansion ()
+{
+  return macro_original_text != 0;
+}
+
+
+void 
+finished_macro_expansion ()
+{
+  /* There'd better be something to pop back to, and we better have
+     saved a pointer to the start of the expanded text.  */
+  gdb_assert (macro_original_text);
+  gdb_assert (macro_expanded_text);
+
+  /* Pop back to the original text.  */
+  lexptr = macro_original_text;
+  macro_original_text = 0;
+
+  /* Free the expanded text.  */
+  xfree (macro_expanded_text);
+  macro_expanded_text = 0;
+}
+
+
+static void
+scan_macro_cleanup (void *dummy)
+{
+  if (macro_original_text)
+    finished_macro_expansion ();
+}
+
+
+/* We set these global variables before calling c_parse, to tell it
+   how it to find macro definitions for the expression at hand.  */
+macro_lookup_ftype *expression_macro_lookup_func;
+void *expression_macro_lookup_baton;
+
+
+static struct macro_definition *
+null_macro_lookup (const char *name, void *baton)
+{
+  return 0;
+}
+
+
+static int
+c_preprocess_and_parse ()
+{
+  /* Set up a lookup function for the macro expander.  */
+  struct macro_scope *scope = 0;
+  struct cleanup *back_to = make_cleanup (free_current_contents, &scope);
+
+  if (expression_context_block)
+    scope = sal_macro_scope (find_pc_line (expression_context_pc, 0));
+  else
+    scope = default_macro_scope ();
+
+  if (scope)
+    {
+      expression_macro_lookup_func = standard_macro_lookup;
+      expression_macro_lookup_baton = (void *) scope;
+    }
+  else
+    {
+      expression_macro_lookup_func = null_macro_lookup;
+      expression_macro_lookup_baton = 0;      
+    }
+
+  gdb_assert (! macro_original_text);
+  make_cleanup (scan_macro_cleanup, 0);
+
+  {
+    int result = c_parse ();
+    do_cleanups (back_to);
+    return result;
+  }
+}
+
+
+
 /* Table mapping opcodes into strings for printing operators
    and precedences of the operators.  */
 
@@ -439,7 +562,7 @@ const struct language_defn c_language_defn =
   range_check_off,
   type_check_off,
   case_sensitive_on,
-  c_parse,
+  c_preprocess_and_parse,
   c_error,
   evaluate_subexp_standard,
   c_printchar,			/* Print a character constant */
@@ -491,7 +614,7 @@ const struct language_defn cplus_language_defn =
   range_check_off,
   type_check_off,
   case_sensitive_on,
-  c_parse,
+  c_preprocess_and_parse,
   c_error,
   evaluate_subexp_standard,
   c_printchar,			/* Print a character constant */
@@ -520,7 +643,7 @@ const struct language_defn asm_language_defn =
   range_check_off,
   type_check_off,
   case_sensitive_on,
-  c_parse,
+  c_preprocess_and_parse,
   c_error,
   evaluate_subexp_standard,
   c_printchar,			/* Print a character constant */
diff --git a/gdb/c-lang.h b/gdb/c-lang.h
index b1925e1e2d..e64d4c69e9 100644
--- a/gdb/c-lang.h
+++ b/gdb/c-lang.h
@@ -24,6 +24,7 @@
 #define C_LANG_H 1
 
 #include "value.h"
+#include "macroexp.h"
 
 
 extern int c_parse (void);	/* Defined in c-exp.y */
@@ -49,6 +50,13 @@ extern void c_printstr (struct ui_file * stream, char *string,
 			unsigned int length, int width,
 			int force_ellipses);
 
+extern void scan_macro_expansion (char *expansion);
+extern int scanning_macro_expansion (void);
+extern void finished_macro_expansion (void);
+
+extern macro_lookup_ftype *expression_macro_lookup_func;
+extern void *expression_macro_lookup_baton;
+
 extern struct type *c_create_fundamental_type (struct objfile *, int);
 
 extern struct type **const (c_builtin_types[]);
diff --git a/gdb/parse.c b/gdb/parse.c
index 9c1f3e16d0..bc81f221b5 100644
--- a/gdb/parse.c
+++ b/gdb/parse.c
@@ -71,6 +71,7 @@ struct expression *expout;
 int expout_size;
 int expout_ptr;
 struct block *expression_context_block;
+CORE_ADDR expression_context_pc;
 struct block *innermost_block;
 int arglist_len;
 union type_stack_elt *type_stack;
@@ -1140,7 +1141,13 @@ parse_exp_1 (char **stringptr, struct block *block, int comma)
   old_chain = make_cleanup (free_funcalls, 0 /*ignore*/);
   funcall_chain = 0;
 
-  expression_context_block = block ? block : get_selected_block (0);
+  if (block)
+    {
+      expression_context_block = block;
+      expression_context_pc = block->startaddr;
+    }
+  else
+    expression_context_block = get_selected_block (&expression_context_pc);
 
   namecopy = (char *) alloca (strlen (lexptr) + 1);
   expout_size = 10;
diff --git a/gdb/parser-defs.h b/gdb/parser-defs.h
index ece2849375..7db1c77e12 100644
--- a/gdb/parser-defs.h
+++ b/gdb/parser-defs.h
@@ -37,6 +37,12 @@ extern int expout_ptr;
 
 extern struct block *expression_context_block;
 
+/* If expression_context_block is non-zero, then this is the PC within
+   the block that we want to evaluate expressions at.  When debugging
+   C or C++ code, we use this to find the exact line we're at, and
+   then look up the macro definitions active at that point.  */
+CORE_ADDR expression_context_pc;
+
 /* The innermost context required by the stack and register variables
    we've encountered so far. */
 extern struct block *innermost_block;