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.

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 */