[rfc] Clear some global variables when reloading object files

[Daniel Jacobowitz <drow at false dot org>]

Mark, I encountered a problem today with expression_context_block that
sounded exactly like what you encountered with innermost_block.  I
suspect the right thing to do would be to clean up the global variables
entirely, but I agree that it would be a terrible mess to untangle,
and this seems like the next best thing.  What do you think?

-- 
Daniel Jacobowitz
CodeSourcery

2006-08-03  Daniel Jacobowitz  <dan@codesourcery.com>

	* Makefile.in (objfiles.o, symfile.o): Update.
	* objfiles.c: Include "expression.h" and "parser-defs.h".
	(free_objfile): Clear global blocks.
	* symfile.c: Include "parser-defs.h".
	(clear_symtab_users): Clear global blocks.

--- Makefile.in	(revision 146239)
+++ Makefile.in	(local)
@@ -2441,7 +2441,8 @@ objc-lang.o: objc-lang.c $(defs_h) $(sym
 objfiles.o: objfiles.c $(defs_h) $(bfd_h) $(symtab_h) $(symfile_h) \
 	$(objfiles_h) $(gdb_stabs_h) $(target_h) $(bcache_h) $(mdebugread_h) \
 	$(gdb_assert_h) $(gdb_stat_h) $(gdb_obstack_h) $(gdb_string_h) \
-	$(hashtab_h) $(breakpoint_h) $(block_h) $(dictionary_h) $(source_h)
+	$(hashtab_h) $(breakpoint_h) $(block_h) $(dictionary_h) $(source_h) \
+	$(parser_defs_h) $(expression_h)
 observer.o: observer.c $(defs_h) $(observer_h) $(command_h) $(gdbcmd_h) \
 	$(observer_inc)
 obsd-tdep.o: obsd-tdep.c $(defs_h) $(frame_h) $(symtab_h) $(obsd_tdep_h)
@@ -2764,7 +2765,8 @@ symfile.o: symfile.c $(defs_h) $(bfdlink
 	$(complaints_h) $(demangle_h) $(inferior_h) $(filenames_h) \
 	$(gdb_stabs_h) $(gdb_obstack_h) $(completer_h) $(bcache_h) \
 	$(hashtab_h) $(readline_h) $(gdb_assert_h) $(block_h) \
-	$(gdb_string_h) $(gdb_stat_h) $(observer_h) $(exec_h)
+	$(gdb_string_h) $(gdb_stat_h) $(observer_h) $(exec_h) \
+	$(parser_defs_h)
 symfile-mem.o: symfile-mem.c $(defs_h) $(symtab_h) $(gdbcore_h) \
 	$(objfiles_h) $(exceptions_h) $(gdbcmd_h) $(target_h) $(value_h) \
 	$(symfile_h) $(observer_h) $(auxv_h) $(elf_common_h)
--- objfiles.c	(revision 146239)
+++ objfiles.c	(local)
@@ -34,6 +34,9 @@
 #include "target.h"
 #include "bcache.h"
 #include "mdebugread.h"
+#include "expression.h"
+#include "parser-defs.h"
+
 #include "gdb_assert.h"
 #include <sys/types.h>
 #include "gdb_stat.h"
@@ -441,6 +444,12 @@ free_objfile (struct objfile *objfile)
      for example), so we need to call this here.  */
   clear_pc_function_cache ();
 
+  /* Clear globals which might have pointed into a removed objfile.
+     FIXME: It's not clear which of these are supposed to persist
+     between expressions and which ought to be reset each time.  */
+  expression_context_block = NULL;
+  innermost_block = NULL;
+
   /* Check to see if the current_source_symtab belongs to this objfile,
      and if so, call clear_current_source_symtab_and_line. */
 
--- symfile.c	(revision 146239)
+++ symfile.c	(local)
@@ -51,6 +51,7 @@
 #include "block.h"
 #include "observer.h"
 #include "exec.h"
+#include "parser-defs.h"
 
 #include <sys/types.h>
 #include <fcntl.h>
@@ -2537,6 +2538,12 @@ clear_symtab_users (void)
   clear_pc_function_cache ();
   if (deprecated_target_new_objfile_hook)
     deprecated_target_new_objfile_hook (NULL);
+
+  /* Clear globals which might have pointed into a removed objfile.
+     FIXME: It's not clear which of these are supposed to persist
+     between expressions and which ought to be reset each time.  */
+  expression_context_block = NULL;
+  innermost_block = NULL;
 }
 
 static void