[3/8] Change fde table to a vector

Message ID 20200208152758.29385-4-tom@tromey.com
State New
Headers show
Series
  • Share DWARF frame information across inferiors
Related show

Commit Message

Tom Tromey Feb. 8, 2020, 3:27 p.m.
This removes struct dwarf2_fde_table, replacing it with a typedef of
std::vector.  This simplifies the code somewhat.

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

	* dwarf2/frame.c (struct dwarf2_fde_table): Remove.
	(dwarf2_fde_table): Typedef for std::vector.
	(dwarf2_frame_objfile_data): Remove the deleter.
	(dwarf2_frame_find_fde, add_fde, decode_frame_entry_1)
	(decode_frame_entry): Update.
	(dwarf2_build_frame_info): Use "new".

Change-Id: Ie31c7413dce2865b76f5f70374ba7a559112ce5e
---
 gdb/ChangeLog      |   9 ++++
 gdb/dwarf2/frame.c | 102 ++++++++++++---------------------------------
 2 files changed, 35 insertions(+), 76 deletions(-)

-- 
2.17.2

Comments

Luis Machado Feb. 11, 2020, 10:26 a.m. | #1
Great cleanup. Just a few comments...

On 2/8/20 12:27 PM, Tom Tromey wrote:
> This removes struct dwarf2_fde_table, replacing it with a typedef of

> std::vector.  This simplifies the code somewhat.

> 

> gdb/ChangeLog

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

> 

> 	* dwarf2/frame.c (struct dwarf2_fde_table): Remove.

> 	(dwarf2_fde_table): Typedef for std::vector.

> 	(dwarf2_frame_objfile_data): Remove the deleter.

> 	(dwarf2_frame_find_fde, add_fde, decode_frame_entry_1)

> 	(decode_frame_entry): Update.

> 	(dwarf2_build_frame_info): Use "new".

> 

> Change-Id: Ie31c7413dce2865b76f5f70374ba7a559112ce5e

> ---

>   gdb/ChangeLog      |   9 ++++

>   gdb/dwarf2/frame.c | 102 ++++++++++++---------------------------------

>   2 files changed, 35 insertions(+), 76 deletions(-)

> 

> diff --git a/gdb/dwarf2/frame.c b/gdb/dwarf2/frame.c

> index db8e5cd25f3..6d87e598345 100644

> --- a/gdb/dwarf2/frame.c

> +++ b/gdb/dwarf2/frame.c

> @@ -129,11 +129,7 @@ struct dwarf2_fde

>     unsigned char eh_frame_p;

>   };

>   

> -struct dwarf2_fde_table

> -{

> -  int num_entries;

> -  struct dwarf2_fde **entries;

> -};

> +typedef std::vector<dwarf2_fde *> dwarf2_fde_table;

>   

>   /* A minimal decoding of DWARF2 compilation units.  We only decode

>      what's needed to get to the call frame information.  */

> @@ -1471,9 +1467,7 @@ dwarf2_frame_cfa (struct frame_info *this_frame)

>     return get_frame_base (this_frame);

>   }

>   

> -const struct objfile_key<dwarf2_fde_table,

> -			 gdb::noop_deleter<dwarf2_fde_table>>

> -  dwarf2_frame_objfile_data;

> +const struct objfile_key<dwarf2_fde_table> dwarf2_frame_objfile_data;

>   

>   

>   

> @@ -1636,7 +1630,7 @@ dwarf2_frame_find_fde (CORE_ADDR *pc, CORE_ADDR *out_offset)

>   {

>     for (objfile *objfile : current_program_space->objfiles ())

>       {

> -      struct dwarf2_fde_table *fde_table;

> +      dwarf2_fde_table *fde_table;

>         CORE_ADDR offset;

>         CORE_ADDR seek_pc;

>   

> @@ -1648,20 +1642,20 @@ dwarf2_frame_find_fde (CORE_ADDR *pc, CORE_ADDR *out_offset)

>   	}

>         gdb_assert (fde_table != NULL);

>   

> -      if (fde_table->num_entries == 0)

> +      if (fde_table->empty ())

>   	continue;

>   

>         gdb_assert (!objfile->section_offsets.empty ());

>         offset = objfile->text_section_offset ();

>   

> -      gdb_assert (fde_table->num_entries > 0);

> -      if (*pc < offset + fde_table->entries[0]->initial_location)

> +      gdb_assert (!fde_table->empty ());

> +      if (*pc < offset + (*fde_table)[0]->initial_location)

>           continue;

>   

>         seek_pc = *pc - offset;

> -      auto end = fde_table->entries + fde_table->num_entries;

> -      auto it = gdb::binary_search (fde_table->entries, end, seek_pc, bsearch_fde_cmp);

> -      if (it != end)

> +      auto it = gdb::binary_search (fde_table->begin (), fde_table->end (),

> +				    seek_pc, bsearch_fde_cmp);

> +      if (it != fde_table->end ())

>           {

>             *pc = (*it)->initial_location + offset;

>   	  if (out_offset)

> @@ -1674,16 +1668,13 @@ dwarf2_frame_find_fde (CORE_ADDR *pc, CORE_ADDR *out_offset)

>   

>   /* Add a pointer to new FDE to the FDE_TABLE, allocating space for it.  */

>   static void


We don't quite allocate space for it anymore, but we do behind the 
scenes. The comment seems slightly stale. Plus the sentence reads a bit 
funny. I'd update this, but i'm fine keeping it too.

> -add_fde (struct dwarf2_fde_table *fde_table, struct dwarf2_fde *fde)

> +add_fde (dwarf2_fde_table *fde_table, struct dwarf2_fde *fde)

>   {

>     if (fde->address_range == 0)

>       /* Discard useless FDEs.  */

>       return;

>   

> -  fde_table->num_entries += 1;

> -  fde_table->entries = XRESIZEVEC (struct dwarf2_fde *, fde_table->entries,

> -				   fde_table->num_entries);

> -  fde_table->entries[fde_table->num_entries - 1] = fde;

> +  fde_table->push_back (fde);

>   }

>   

>   #define DW64_CIE_ID 0xffffffffffffffffULL

> @@ -1702,7 +1693,7 @@ static const gdb_byte *decode_frame_entry (struct comp_unit *unit,

>   					   const gdb_byte *start,

>   					   int eh_frame_p,

>   					   dwarf2_cie_table &cie_table,

> -					   struct dwarf2_fde_table *fde_table,

> +					   dwarf2_fde_table *fde_table,

>   					   enum eh_frame_type entry_type);

>   

>   /* Decode the next CIE or FDE, entry_type specifies the expected type.

> @@ -1712,7 +1703,7 @@ static const gdb_byte *

>   decode_frame_entry_1 (struct comp_unit *unit, const gdb_byte *start,

>   		      int eh_frame_p,

>                         dwarf2_cie_table &cie_table,

> -                      struct dwarf2_fde_table *fde_table,

> +                      dwarf2_fde_table *fde_table,

>                         enum eh_frame_type entry_type)

>   {

>     struct gdbarch *gdbarch = get_objfile_arch (unit->objfile);

> @@ -2014,7 +2005,7 @@ static const gdb_byte *

>   decode_frame_entry (struct comp_unit *unit, const gdb_byte *start,

>   		    int eh_frame_p,

>   		    dwarf2_cie_table &cie_table,

> -                    struct dwarf2_fde_table *fde_table,

> +                    dwarf2_fde_table *fde_table,

>                       enum eh_frame_type entry_type)

>   {

>     enum { NONE, ALIGN4, ALIGN8, FAIL } workaround = NONE;

> @@ -2128,11 +2119,8 @@ dwarf2_build_frame_info (struct objfile *objfile)

>     struct comp_unit *unit;

>     const gdb_byte *frame_ptr;

>     dwarf2_cie_table cie_table;

> -  struct dwarf2_fde_table fde_table;

> -  struct dwarf2_fde_table *fde_table2;

> -

> -  fde_table.num_entries = 0;

> -  fde_table.entries = NULL;

> +  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);

> @@ -2181,12 +2169,7 @@ dwarf2_build_frame_info (struct objfile *objfile)

>   	      warning (_("skipping .eh_frame info of %s: %s"),

>   		       objfile_name (objfile), e.what ());

>   

> -	      if (fde_table.num_entries != 0)

> -		{

> -                  xfree (fde_table.entries);

> -		  fde_table.entries = NULL;

> -		  fde_table.num_entries = 0;

> -		}

> +	      fde_table.clear ();

>   	      /* The cie_table is discarded below.  */

>   	    }

>   

> @@ -2200,7 +2183,7 @@ dwarf2_build_frame_info (struct objfile *objfile)

>                              &unit->dwarf_frame_size);

>     if (unit->dwarf_frame_size)

>       {

> -      int num_old_fde_entries = fde_table.num_entries;

> +      size_t num_old_fde_entries = fde_table.size ();

>   

>         try

>   	{

> @@ -2215,42 +2198,20 @@ dwarf2_build_frame_info (struct objfile *objfile)

>   	  warning (_("skipping .debug_frame info of %s: %s"),

>   		   objfile_name (objfile), e.what ());

>   

> -	  if (fde_table.num_entries != 0)

> -	    {

> -	      fde_table.num_entries = num_old_fde_entries;

> -	      if (num_old_fde_entries == 0)

> -		{

> -		  xfree (fde_table.entries);

> -		  fde_table.entries = NULL;

> -		}

> -	      else

> -		{

> -		  fde_table.entries

> -		    = XRESIZEVEC (struct dwarf2_fde *, fde_table.entries,

> -				  fde_table.num_entries);

> -		}

> -	    }

> -	  fde_table.num_entries = num_old_fde_entries;

> +	  fde_table.resize (num_old_fde_entries);


Took me a bit to figure out the code above. Quite convoluted in its use 
of the size variables. But the new code looks sane as far as i can tell.

>   	}

>       }

>   

>     /* Copy fde_table to obstack: it is needed at runtime.  */

> -  fde_table2 = XOBNEW (&objfile->objfile_obstack, struct dwarf2_fde_table);

> +  fde_table2 = new dwarf2_fde_table; >


The comment mentioning obstack is now obsolete and can be removed.

> -  if (fde_table.num_entries == 0)

> -    {

> -      fde_table2->entries = NULL;

> -      fde_table2->num_entries = 0;

> -    }

> -  else

> +  if (!fde_table.empty ())

>       {

>         struct dwarf2_fde *fde_prev = NULL;

>         struct dwarf2_fde *first_non_zero_fde = NULL;

> -      int i;

>   

>         /* Prepare FDE table for lookups.  */

> -      std::sort (fde_table.entries, fde_table.entries + fde_table.num_entries,

> -		 fde_is_less_than);

> +      std::sort (fde_table.begin (), fde_table.end (), fde_is_less_than);

>   

>         /* Check for leftovers from --gc-sections.  The GNU linker sets

>   	 the relevant symbols to zero, but doesn't zero the FDE *end*

> @@ -2264,10 +2225,8 @@ dwarf2_build_frame_info (struct objfile *objfile)

>   	 Start by finding the first FDE with non-zero start.  Below

>   	 we'll discard all FDEs that start at zero and overlap this

>   	 one.  */

> -      for (i = 0; i < fde_table.num_entries; i++)

> +      for (struct dwarf2_fde *fde : fde_table)

>   	{

> -	  struct dwarf2_fde *fde = fde_table.entries[i];

> -

>   	  if (fde->initial_location != 0)

>   	    {

>   	      first_non_zero_fde = fde;

> @@ -2278,11 +2237,8 @@ dwarf2_build_frame_info (struct objfile *objfile)

>         /* Since we'll be doing bsearch, squeeze out identical (except

>   	 for eh_frame_p) fde entries so bsearch result is predictable.

>   	 Also discard leftovers from --gc-sections.  */

> -      fde_table2->num_entries = 0;

> -      for (i = 0; i < fde_table.num_entries; i++)

> +      for (struct dwarf2_fde *fde : fde_table)

>   	{

> -	  struct dwarf2_fde *fde = fde_table.entries[i];

> -

>   	  if (fde->initial_location == 0

>   	      && first_non_zero_fde != NULL

>   	      && (first_non_zero_fde->initial_location

> @@ -2293,16 +2249,10 @@ dwarf2_build_frame_info (struct objfile *objfile)

>   	      && fde_prev->initial_location == fde->initial_location)

>   	    continue;

>   

> -	  obstack_grow (&objfile->objfile_obstack, &fde_table.entries[i],

> -			sizeof (fde_table.entries[0]));

> -	  ++fde_table2->num_entries;

> +	  fde_table2->push_back (fde);

>   	  fde_prev = fde;

>   	}

> -      fde_table2->entries

> -	= (struct dwarf2_fde **) obstack_finish (&objfile->objfile_obstack);

> -

> -      /* Discard the original fde_table.  */

> -      xfree (fde_table.entries);

> +      fde_table2->shrink_to_fit ();

>       }

>   

>     dwarf2_frame_objfile_data.set (objfile, fde_table2);

> 


Otherwise LGTM.
Tom Tromey Feb. 12, 2020, 12:28 a.m. | #2
>>>>> "Luis" == Luis Machado <luis.machado@linaro.org> writes:


Luis> We don't quite allocate space for it anymore, but we do behind the
Luis> scenes. The comment seems slightly stale. Plus the sentence reads a
Luis> bit funny. I'd update this, but i'm fine keeping it too.

I simplified it to just:

    /* Add FDE to FDE_TABLE.  */

>> /* Copy fde_table to obstack: it is needed at runtime.  */

>> -  fde_table2 = XOBNEW (&objfile->objfile_obstack, struct dwarf2_fde_table);

>> +  fde_table2 = new dwarf2_fde_table; >


Luis> The comment mentioning obstack is now obsolete and can be removed.

I've removed it.  I think this is the one you mentioned in another patch
review -- but it is simple enough to just zap it here and fix up the
conflict.

Tom
Simon Marchi Feb. 12, 2020, 3:28 a.m. | #3
On 2020-02-08 10:27 a.m., Tom Tromey wrote:
> diff --git a/gdb/dwarf2/frame.c b/gdb/dwarf2/frame.c

> index db8e5cd25f3..6d87e598345 100644

> --- a/gdb/dwarf2/frame.c

> +++ b/gdb/dwarf2/frame.c

> @@ -129,11 +129,7 @@ struct dwarf2_fde

>    unsigned char eh_frame_p;

>  };

>  

> -struct dwarf2_fde_table

> -{

> -  int num_entries;

> -  struct dwarf2_fde **entries;

> -};

> +typedef std::vector<dwarf2_fde *> dwarf2_fde_table;


As a further change, I think we could consider make this a vector of objects, rather
than a vector of pointers.

>  /* A minimal decoding of DWARF2 compilation units.  We only decode

>     what's needed to get to the call frame information.  */

> @@ -1471,9 +1467,7 @@ dwarf2_frame_cfa (struct frame_info *this_frame)

>    return get_frame_base (this_frame);

>  }

>  

> -const struct objfile_key<dwarf2_fde_table,

> -			 gdb::noop_deleter<dwarf2_fde_table>>

> -  dwarf2_frame_objfile_data;

> +const struct objfile_key<dwarf2_fde_table> dwarf2_frame_objfile_data;


Can you make this static, while at it?

> @@ -2215,42 +2198,20 @@ dwarf2_build_frame_info (struct objfile *objfile)

>  	  warning (_("skipping .debug_frame info of %s: %s"),

>  		   objfile_name (objfile), e.what ());

>  

> -	  if (fde_table.num_entries != 0)

> -	    {

> -	      fde_table.num_entries = num_old_fde_entries;

> -	      if (num_old_fde_entries == 0)

> -		{

> -		  xfree (fde_table.entries);

> -		  fde_table.entries = NULL;

> -		}

> -	      else

> -		{

> -		  fde_table.entries

> -		    = XRESIZEVEC (struct dwarf2_fde *, fde_table.entries,

> -				  fde_table.num_entries);

> -		}

> -	    }

> -	  fde_table.num_entries = num_old_fde_entries;

> +	  fde_table.resize (num_old_fde_entries);

>  	}

>      }

>  

>    /* Copy fde_table to obstack: it is needed at runtime.  */


I think that comment is stale.

> -  fde_table2 = XOBNEW (&objfile->objfile_obstack, struct dwarf2_fde_table);

> +  fde_table2 = new dwarf2_fde_table;

>  

> -  if (fde_table.num_entries == 0)

> -    {

> -      fde_table2->entries = NULL;

> -      fde_table2->num_entries = 0;

> -    }

> -  else

> +  if (!fde_table.empty ())


If you want to simplify the code even further, you could get rid of this check, since the
code below should cope well with an empty vector.

> @@ -2293,16 +2249,10 @@ dwarf2_build_frame_info (struct objfile *objfile)

>  	      && fde_prev->initial_location == fde->initial_location)

>  	    continue;

>  

> -	  obstack_grow (&objfile->objfile_obstack, &fde_table.entries[i],

> -			sizeof (fde_table.entries[0]));

> -	  ++fde_table2->num_entries;

> +	  fde_table2->push_back (fde);

>  	  fde_prev = fde;

>  	}

> -      fde_table2->entries

> -	= (struct dwarf2_fde **) obstack_finish (&objfile->objfile_obstack);

> -

> -      /* Discard the original fde_table.  */

> -      xfree (fde_table.entries);

> +      fde_table2->shrink_to_fit ();


That shrink_to_fit appears to be pointless, as fde_table2 is created empty and we only
push_back.  Maybe you meant to create it with an initial size?

Simon
Simon Marchi Feb. 12, 2020, 3:33 a.m. | #4
>> @@ -2215,42 +2198,20 @@ dwarf2_build_frame_info (struct objfile *objfile)

>>  	  warning (_("skipping .debug_frame info of %s: %s"),

>>  		   objfile_name (objfile), e.what ());

>>  

>> -	  if (fde_table.num_entries != 0)

>> -	    {

>> -	      fde_table.num_entries = num_old_fde_entries;

>> -	      if (num_old_fde_entries == 0)

>> -		{

>> -		  xfree (fde_table.entries);

>> -		  fde_table.entries = NULL;

>> -		}

>> -	      else

>> -		{

>> -		  fde_table.entries

>> -		    = XRESIZEVEC (struct dwarf2_fde *, fde_table.entries,

>> -				  fde_table.num_entries);

>> -		}

>> -	    }

>> -	  fde_table.num_entries = num_old_fde_entries;

>> +	  fde_table.resize (num_old_fde_entries);

>>  	}

>>      }

>>  

>>    /* Copy fde_table to obstack: it is needed at runtime.  */

> 

> I think that comment is stale.


Sorry, I just noticed that Luis had already pointed this out.

Simon
Tom Tromey Feb. 12, 2020, 10:36 p.m. | #5
>>>>> "Simon" == Simon Marchi <simark@simark.ca> writes:


Simon> As a further change, I think we could consider make this a vector
Simon> of objects, rather than a vector of pointers.

I think I'd rather leave this for a future change.
It makes the patch a lot less obvious, to me anyway.  find_fde returns a
pointer -- but is that safe?  I think so, but I am not 100% certain; but
with the current code it definitely is.

>> +const struct objfile_key<dwarf2_fde_table> dwarf2_frame_objfile_data;


Simon> Can you make this static, while at it?

I did this.

>> +  if (!fde_table.empty ())


Simon> If you want to simplify the code even further, you could get rid
Simon> of this check, since the code below should cope well with an
Simon> empty vector.

Thanks, I did this too.

>> +      fde_table2->shrink_to_fit ();


Simon> That shrink_to_fit appears to be pointless, as fde_table2 is
Simon> created empty and we only push_back.  Maybe you meant to create
Simon> it with an initial size?

IIUC push_back normally uses some resize factor; the shrink_to_fit is a
request to discard any excess memory allocated this way.

FWIW another thing that could be done in this code is to use the
remove_if to remove elements in-place from fde_table.  This is another
thing I'd rather do separately.

Tom
Simon Marchi Feb. 12, 2020, 10:47 p.m. | #6
On 2020-02-12 5:36 p.m., Tom Tromey wrote:
> Simon> That shrink_to_fit appears to be pointless, as fde_table2 is

> Simon> created empty and we only push_back.  Maybe you meant to create

> Simon> it with an initial size?

> 

> IIUC push_back normally uses some resize factor; the shrink_to_fit is a

> request to discard any excess memory allocated this way.


Of course, my bad.

Simon

Patch

diff --git a/gdb/dwarf2/frame.c b/gdb/dwarf2/frame.c
index db8e5cd25f3..6d87e598345 100644
--- a/gdb/dwarf2/frame.c
+++ b/gdb/dwarf2/frame.c
@@ -129,11 +129,7 @@  struct dwarf2_fde
   unsigned char eh_frame_p;
 };
 
-struct dwarf2_fde_table
-{
-  int num_entries;
-  struct dwarf2_fde **entries;
-};
+typedef std::vector<dwarf2_fde *> dwarf2_fde_table;
 
 /* A minimal decoding of DWARF2 compilation units.  We only decode
    what's needed to get to the call frame information.  */
@@ -1471,9 +1467,7 @@  dwarf2_frame_cfa (struct frame_info *this_frame)
   return get_frame_base (this_frame);
 }
 
-const struct objfile_key<dwarf2_fde_table,
-			 gdb::noop_deleter<dwarf2_fde_table>>
-  dwarf2_frame_objfile_data;
+const struct objfile_key<dwarf2_fde_table> dwarf2_frame_objfile_data;
 
 
 
@@ -1636,7 +1630,7 @@  dwarf2_frame_find_fde (CORE_ADDR *pc, CORE_ADDR *out_offset)
 {
   for (objfile *objfile : current_program_space->objfiles ())
     {
-      struct dwarf2_fde_table *fde_table;
+      dwarf2_fde_table *fde_table;
       CORE_ADDR offset;
       CORE_ADDR seek_pc;
 
@@ -1648,20 +1642,20 @@  dwarf2_frame_find_fde (CORE_ADDR *pc, CORE_ADDR *out_offset)
 	}
       gdb_assert (fde_table != NULL);
 
-      if (fde_table->num_entries == 0)
+      if (fde_table->empty ())
 	continue;
 
       gdb_assert (!objfile->section_offsets.empty ());
       offset = objfile->text_section_offset ();
 
-      gdb_assert (fde_table->num_entries > 0);
-      if (*pc < offset + fde_table->entries[0]->initial_location)
+      gdb_assert (!fde_table->empty ());
+      if (*pc < offset + (*fde_table)[0]->initial_location)
         continue;
 
       seek_pc = *pc - offset;
-      auto end = fde_table->entries + fde_table->num_entries;
-      auto it = gdb::binary_search (fde_table->entries, end, seek_pc, bsearch_fde_cmp);
-      if (it != end)
+      auto it = gdb::binary_search (fde_table->begin (), fde_table->end (),
+				    seek_pc, bsearch_fde_cmp);
+      if (it != fde_table->end ())
         {
           *pc = (*it)->initial_location + offset;
 	  if (out_offset)
@@ -1674,16 +1668,13 @@  dwarf2_frame_find_fde (CORE_ADDR *pc, CORE_ADDR *out_offset)
 
 /* Add a pointer to new FDE to the FDE_TABLE, allocating space for it.  */
 static void
-add_fde (struct dwarf2_fde_table *fde_table, struct dwarf2_fde *fde)
+add_fde (dwarf2_fde_table *fde_table, struct dwarf2_fde *fde)
 {
   if (fde->address_range == 0)
     /* Discard useless FDEs.  */
     return;
 
-  fde_table->num_entries += 1;
-  fde_table->entries = XRESIZEVEC (struct dwarf2_fde *, fde_table->entries,
-				   fde_table->num_entries);
-  fde_table->entries[fde_table->num_entries - 1] = fde;
+  fde_table->push_back (fde);
 }
 
 #define DW64_CIE_ID 0xffffffffffffffffULL
@@ -1702,7 +1693,7 @@  static const gdb_byte *decode_frame_entry (struct comp_unit *unit,
 					   const gdb_byte *start,
 					   int eh_frame_p,
 					   dwarf2_cie_table &cie_table,
-					   struct dwarf2_fde_table *fde_table,
+					   dwarf2_fde_table *fde_table,
 					   enum eh_frame_type entry_type);
 
 /* Decode the next CIE or FDE, entry_type specifies the expected type.
@@ -1712,7 +1703,7 @@  static const gdb_byte *
 decode_frame_entry_1 (struct comp_unit *unit, const gdb_byte *start,
 		      int eh_frame_p,
                       dwarf2_cie_table &cie_table,
-                      struct dwarf2_fde_table *fde_table,
+                      dwarf2_fde_table *fde_table,
                       enum eh_frame_type entry_type)
 {
   struct gdbarch *gdbarch = get_objfile_arch (unit->objfile);
@@ -2014,7 +2005,7 @@  static const gdb_byte *
 decode_frame_entry (struct comp_unit *unit, const gdb_byte *start,
 		    int eh_frame_p,
 		    dwarf2_cie_table &cie_table,
-                    struct dwarf2_fde_table *fde_table,
+                    dwarf2_fde_table *fde_table,
                     enum eh_frame_type entry_type)
 {
   enum { NONE, ALIGN4, ALIGN8, FAIL } workaround = NONE;
@@ -2128,11 +2119,8 @@  dwarf2_build_frame_info (struct objfile *objfile)
   struct comp_unit *unit;
   const gdb_byte *frame_ptr;
   dwarf2_cie_table cie_table;
-  struct dwarf2_fde_table fde_table;
-  struct dwarf2_fde_table *fde_table2;
-
-  fde_table.num_entries = 0;
-  fde_table.entries = NULL;
+  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);
@@ -2181,12 +2169,7 @@  dwarf2_build_frame_info (struct objfile *objfile)
 	      warning (_("skipping .eh_frame info of %s: %s"),
 		       objfile_name (objfile), e.what ());
 
-	      if (fde_table.num_entries != 0)
-		{
-                  xfree (fde_table.entries);
-		  fde_table.entries = NULL;
-		  fde_table.num_entries = 0;
-		}
+	      fde_table.clear ();
 	      /* The cie_table is discarded below.  */
 	    }
 
@@ -2200,7 +2183,7 @@  dwarf2_build_frame_info (struct objfile *objfile)
                            &unit->dwarf_frame_size);
   if (unit->dwarf_frame_size)
     {
-      int num_old_fde_entries = fde_table.num_entries;
+      size_t num_old_fde_entries = fde_table.size ();
 
       try
 	{
@@ -2215,42 +2198,20 @@  dwarf2_build_frame_info (struct objfile *objfile)
 	  warning (_("skipping .debug_frame info of %s: %s"),
 		   objfile_name (objfile), e.what ());
 
-	  if (fde_table.num_entries != 0)
-	    {
-	      fde_table.num_entries = num_old_fde_entries;
-	      if (num_old_fde_entries == 0)
-		{
-		  xfree (fde_table.entries);
-		  fde_table.entries = NULL;
-		}
-	      else
-		{
-		  fde_table.entries
-		    = XRESIZEVEC (struct dwarf2_fde *, fde_table.entries,
-				  fde_table.num_entries);
-		}
-	    }
-	  fde_table.num_entries = num_old_fde_entries;
+	  fde_table.resize (num_old_fde_entries);
 	}
     }
 
   /* Copy fde_table to obstack: it is needed at runtime.  */
-  fde_table2 = XOBNEW (&objfile->objfile_obstack, struct dwarf2_fde_table);
+  fde_table2 = new dwarf2_fde_table;
 
-  if (fde_table.num_entries == 0)
-    {
-      fde_table2->entries = NULL;
-      fde_table2->num_entries = 0;
-    }
-  else
+  if (!fde_table.empty ())
     {
       struct dwarf2_fde *fde_prev = NULL;
       struct dwarf2_fde *first_non_zero_fde = NULL;
-      int i;
 
       /* Prepare FDE table for lookups.  */
-      std::sort (fde_table.entries, fde_table.entries + fde_table.num_entries,
-		 fde_is_less_than);
+      std::sort (fde_table.begin (), fde_table.end (), fde_is_less_than);
 
       /* Check for leftovers from --gc-sections.  The GNU linker sets
 	 the relevant symbols to zero, but doesn't zero the FDE *end*
@@ -2264,10 +2225,8 @@  dwarf2_build_frame_info (struct objfile *objfile)
 	 Start by finding the first FDE with non-zero start.  Below
 	 we'll discard all FDEs that start at zero and overlap this
 	 one.  */
-      for (i = 0; i < fde_table.num_entries; i++)
+      for (struct dwarf2_fde *fde : fde_table)
 	{
-	  struct dwarf2_fde *fde = fde_table.entries[i];
-
 	  if (fde->initial_location != 0)
 	    {
 	      first_non_zero_fde = fde;
@@ -2278,11 +2237,8 @@  dwarf2_build_frame_info (struct objfile *objfile)
       /* Since we'll be doing bsearch, squeeze out identical (except
 	 for eh_frame_p) fde entries so bsearch result is predictable.
 	 Also discard leftovers from --gc-sections.  */
-      fde_table2->num_entries = 0;
-      for (i = 0; i < fde_table.num_entries; i++)
+      for (struct dwarf2_fde *fde : fde_table)
 	{
-	  struct dwarf2_fde *fde = fde_table.entries[i];
-
 	  if (fde->initial_location == 0
 	      && first_non_zero_fde != NULL
 	      && (first_non_zero_fde->initial_location
@@ -2293,16 +2249,10 @@  dwarf2_build_frame_info (struct objfile *objfile)
 	      && fde_prev->initial_location == fde->initial_location)
 	    continue;
 
-	  obstack_grow (&objfile->objfile_obstack, &fde_table.entries[i],
-			sizeof (fde_table.entries[0]));
-	  ++fde_table2->num_entries;
+	  fde_table2->push_back (fde);
 	  fde_prev = fde;
 	}
-      fde_table2->entries
-	= (struct dwarf2_fde **) obstack_finish (&objfile->objfile_obstack);
-
-      /* Discard the original fde_table.  */
-      xfree (fde_table.entries);
+      fde_table2->shrink_to_fit ();
     }
 
   dwarf2_frame_objfile_data.set (objfile, fde_table2);