[patch] Fix DW_OP_call2 and DW_OP_call4 for max-cache-age 0

[Jan Kratochvil <jan dot kratochvil at redhat dot com>]

Hi,

as discussed on #gdb when you set max-cache-age 0 DW_OP_call{2,4} crashed GDB.

I admit I rather did not test max-cache-age 0 globally.

No regressions on {x86_64,x86_64-m32,i686}-fedora14snapshot-linux-gnu.

OK to check-in?

The problem is not reproducible with max-cache-age 1.  Without the
dw2_do_instantiate_symtab patch part GDB no longer crashes on max-cache-age 0
but it will then error out on DW_OP_call{2,4} with that:
+    error (_("Dwarf Error: Cannot read CU for DIE at 0x%x referenced "
+	     "in module %s"),

There is a bit weird that functions with parameter per_cu have also parameter
objfile when there is per_cu->objfile.  It is because per_cu->objfile is there
only since cf9fe5cf2be8b76820a05c966cdca6df5c2eee24 (Tom Tromey 2010-07-13).


Thanks,
Jan


gdb/
2010-08-23  Jan Kratochvil  <jan.kratochvil@redhat.com>

	* dwarf2read.c (dw2_do_instantiate_symtab): Move the
	age_cached_comp_units call to the top, extend its comment.
	(dwarf2_fetch_die_location_block): Initialize cu later.  Call
	dw2_setup and dw2_do_instantiate_symtab if PER_CU->CU is NULL.

gdb/testsuite/
2010-08-23  Jan Kratochvil  <jan.kratochvil@redhat.com>

	* gdb.dwarf2/dw2-op-call.exp (maintenance set dwarf2 max-cache-age 0):
	New test.

--- a/gdb/dwarf2read.c
+++ b/gdb/dwarf2read.c
@@ -1636,6 +1636,11 @@ dw2_do_instantiate_symtab (struct objfile *objfile,
 {
   struct cleanup *back_to;
 
+  /* Age the cache, releasing compilation units that have not been used
+     recently.  Age them first so that we do not age out the requested PER_CU
+     unit if DWARF2_MAX_CACHE_AGE is too low.  */
+  age_cached_comp_units ();
+
   back_to = make_cleanup (dwarf2_release_queue, NULL);
 
   queue_comp_unit (per_cu, objfile);
@@ -1647,10 +1652,6 @@ dw2_do_instantiate_symtab (struct objfile *objfile,
 
   process_queue (objfile);
 
-  /* Age the cache, releasing compilation units that have not
-     been used recently.  */
-  age_cached_comp_units ();
-
   do_cleanups (back_to);
 }
 
@@ -12720,11 +12721,22 @@ struct dwarf2_locexpr_baton
 dwarf2_fetch_die_location_block (unsigned int offset,
 				 struct dwarf2_per_cu_data *per_cu)
 {
-  struct dwarf2_cu *cu = per_cu->cu;
+  struct dwarf2_cu *cu;
   struct die_info *die;
   struct attribute *attr;
   struct dwarf2_locexpr_baton retval;
 
+  if (per_cu->cu == NULL)
+    {
+      dw2_setup (per_cu->objfile);
+      dw2_do_instantiate_symtab (per_cu->objfile, per_cu);
+    }
+  if (per_cu->cu == NULL)
+    error (_("Dwarf Error: Cannot read CU for DIE at 0x%x referenced "
+	     "in module %s"),
+	   offset, per_cu->objfile->name);
+
+  cu = per_cu->cu;
   die = follow_die_offset (offset, &cu);
   if (!die)
     error (_("Dwarf Error: Cannot find DIE at 0x%x referenced in module %s"),
--- a/gdb/testsuite/gdb.dwarf2/dw2-op-call.exp
+++ b/gdb/testsuite/gdb.dwarf2/dw2-op-call.exp
@@ -36,6 +36,9 @@ if  { [gdb_compile "${srcdir}/${subdir}/${srcfile}" "${objdir}/${subdir}/${execu
 
 clean_restart $executable
 
+# Additional test to verify the referenced CU is not aged out.
+gdb_test_no_output "maintenance set dwarf2 max-cache-age 0"
+
 gdb_test "p array1" " = 1"
 gdb_test "p array2" " = 2" "array2 using DW_OP_call2"
 gdb_test "p array3" " = 3" "array3 using DW_OP_call4"