[PATCH 4/8] Store the comp_unit instead of the FDE table

[Tom Tromey <tom@tromey.com>]

This changes the DWARF frame code to store the comp_unit on the
objfile, rather than storing the FDE table.  It also changes the
comp_unit to be heap-allocated using "new".

This change makes it simpler for a later patch to add a field to the
comp_unit, and to have deallaction work properly.  This in turn is
important for making the frame data be independent of the objfile.

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

	* dwarf2/frame.c (struct comp_unit): Add initializers.
	(dwarf2_frame_objfile_data): Store a comp_unit.
	(dwarf2_frame_find_fde): Update.
	(dwarf2_build_frame_info): Use "new".

Change-Id: Id339892824caf47e7909ed5ee7e2f0556d645dba
---
 gdb/ChangeLog      |  7 +++++++
 gdb/dwarf2/frame.c | 43 ++++++++++++++++++++-----------------------
 2 files changed, 27 insertions(+), 23 deletions(-)

diff --git a/gdb/dwarf2/frame.c b/gdb/dwarf2/frame.c
index 6d87e598345..0e74b8e7e68 100644
--- a/gdb/dwarf2/frame.c
+++ b/gdb/dwarf2/frame.c
@@ -137,24 +137,27 @@ typedef std::vector<dwarf2_fde *> dwarf2_fde_table;
 struct comp_unit
 {
   /* Keep the bfd convenient.  */
-  bfd *abfd;
+  bfd *abfd = nullptr;
 
-  struct objfile *objfile;
+  struct objfile *objfile = nullptr;
 
   /* Pointer to the .debug_frame section loaded into memory.  */
-  const gdb_byte *dwarf_frame_buffer;
+  const gdb_byte *dwarf_frame_buffer = nullptr;
 
   /* Length of the loaded .debug_frame section.  */
-  bfd_size_type dwarf_frame_size;
+  bfd_size_type dwarf_frame_size = 0;
 
   /* Pointer to the .debug_frame section.  */
-  asection *dwarf_frame_section;
+  asection *dwarf_frame_section = nullptr;
 
   /* Base for DW_EH_PE_datarel encodings.  */
-  bfd_vma dbase;
+  bfd_vma dbase = 0;
 
   /* Base for DW_EH_PE_textrel encodings.  */
-  bfd_vma tbase;
+  bfd_vma tbase = 0;
+
+  /* The FDE table.  */
+  dwarf2_fde_table fde_table;
 };
 
 static struct dwarf2_fde *dwarf2_frame_find_fde (CORE_ADDR *pc,
@@ -1467,7 +1470,7 @@ dwarf2_frame_cfa (struct frame_info *this_frame)
   return get_frame_base (this_frame);
 }
 \f
-const struct objfile_key<dwarf2_fde_table> dwarf2_frame_objfile_data;
+const struct objfile_key<comp_unit> dwarf2_frame_objfile_data;
 
 \f
 
@@ -1630,18 +1633,18 @@ dwarf2_frame_find_fde (CORE_ADDR *pc, CORE_ADDR *out_offset)
 {
   for (objfile *objfile : current_program_space->objfiles ())
     {
-      dwarf2_fde_table *fde_table;
       CORE_ADDR offset;
       CORE_ADDR seek_pc;
 
-      fde_table = dwarf2_frame_objfile_data.get (objfile);
-      if (fde_table == NULL)
+      comp_unit *unit = dwarf2_frame_objfile_data.get (objfile);
+      if (unit == NULL)
 	{
 	  dwarf2_build_frame_info (objfile);
-	  fde_table = dwarf2_frame_objfile_data.get (objfile);
+	  unit = dwarf2_frame_objfile_data.get (objfile);
 	}
-      gdb_assert (fde_table != NULL);
+      gdb_assert (unit != NULL);
 
+      dwarf2_fde_table *fde_table = &unit->fde_table;
       if (fde_table->empty ())
 	continue;
 
@@ -2120,14 +2123,11 @@ dwarf2_build_frame_info (struct objfile *objfile)
   const gdb_byte *frame_ptr;
   dwarf2_cie_table cie_table;
   dwarf2_fde_table fde_table;
-  dwarf2_fde_table *fde_table2;
 
   /* Build a minimal decoding of the DWARF2 compilation unit.  */
-  unit = XOBNEW (&objfile->objfile_obstack, comp_unit);
+  unit = new comp_unit;
   unit->abfd = objfile->obfd;
   unit->objfile = objfile;
-  unit->dbase = 0;
-  unit->tbase = 0;
 
   if (objfile->separate_debug_objfile_backlink == NULL)
     {
@@ -2202,9 +2202,6 @@ dwarf2_build_frame_info (struct objfile *objfile)
 	}
     }
 
-  /* Copy fde_table to obstack: it is needed at runtime.  */
-  fde_table2 = new dwarf2_fde_table;
-
   if (!fde_table.empty ())
     {
       struct dwarf2_fde *fde_prev = NULL;
@@ -2249,13 +2246,13 @@ dwarf2_build_frame_info (struct objfile *objfile)
 	      && fde_prev->initial_location == fde->initial_location)
 	    continue;
 
-	  fde_table2->push_back (fde);
+	  unit->fde_table.push_back (fde);
 	  fde_prev = fde;
 	}
-      fde_table2->shrink_to_fit ();
+      unit->fde_table.shrink_to_fit ();
     }
 
-  dwarf2_frame_objfile_data.set (objfile, fde_table2);
+  dwarf2_frame_objfile_data.set (objfile, unit);
 }
 
 /* Handle 'maintenance show dwarf unwinders'.  */
-- 
2.17.2