[PATCH 5/8] Add per-unit obstack

[Tom Tromey]

This adds an auto_obstack to the DWARF frame comp_unit object, and
then changes the remaining code here to use the comp_unit obstack
rather than the objfile obstack.

At this point, all the storage for frame data is self-contained --
that is, it is independent of the objfile.

gdb/ChangeLog
2020-02-08  Tom Tromey  <tom@tromey.com>

	* dwarf2/frame.c (struct comp_unit) <obstack>: New member.
	(decode_frame_entry_1): Use the comp_unit obstack.

Change-Id: I8a1af090bcc2811762a38afbbea1512be7d952fb
---
 gdb/ChangeLog      | 5 +++++
 gdb/dwarf2/frame.c | 7 +++++--
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/gdb/dwarf2/frame.c b/gdb/dwarf2/frame.c
index 0e74b8e7e68..7e1a744513b 100644
--- a/gdb/dwarf2/frame.c
+++ b/gdb/dwarf2/frame.c
@@ -158,6 +158,9 @@ struct comp_unit
 
   /* The FDE table.  */
   dwarf2_fde_table fde_table;
+
+  /* Hold data used by this module.  */
+  auto_obstack obstack;
 };
 
 static struct dwarf2_fde *dwarf2_frame_find_fde (CORE_ADDR *pc,
@@ -1771,7 +1774,7 @@ decode_frame_entry_1 (struct comp_unit *unit, const gdb_byte *start,
       if (find_cie (cie_table, cie_pointer))
 	return end;
 
-      cie = XOBNEW (&unit->objfile->objfile_obstack, struct dwarf2_cie);
+      cie = XOBNEW (&unit->obstack, struct dwarf2_cie);
       cie->initial_instructions = NULL;
       cie->cie_pointer = cie_pointer;
 
@@ -1950,7 +1953,7 @@ decode_frame_entry_1 (struct comp_unit *unit, const gdb_byte *start,
       if (cie_pointer >= unit->dwarf_frame_size)
 	return NULL;
 
-      fde = XOBNEW (&unit->objfile->objfile_obstack, struct dwarf2_fde);
+      fde = XOBNEW (&unit->obstack, struct dwarf2_fde);
       fde->cie = find_cie (cie_table, cie_pointer);
       if (fde->cie == NULL)
 	{
-- 
2.17.2