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Manage objfiles with shared_ptr 

This changes objfiles to be managed using a shared_ptr.  shared_ptr is
chosen because it enables the use of objfiles in background threads.

The simplest way to do this was to introduce a new iterator that will
return the underlying objfile, rather than a shared_ptr.  (I also
tried changing the rest of gdb to use shared_ptr, but this was quite
large; and to using intrusive reference counting, but this also was
tricky.)

gdb/ChangeLog
2019-12-12  Tom Tromey  <tom@tromey.com>

	* progspace.h (objfile_list): New typedef.
	(class unwrapping_objfile_iterator)
	(struct unwrapping_objfile_range): Newl
	(struct program_space) <objfiles_range>: Change type.
	<objfiles>: Change return type.
	<add_objfile>: Change type of "objfile" parameter.
	<objfiles_list>: Now a list of shared_ptr.
	* progspace.c (program_space::add_objfile): Change type of
	"objfile".  Update.
	(program_space::remove_objfile): Update.
	* objfiles.h (struct objfile) <~objfile>: Make public.
	* objfiles.c (objfile::make): Update.
	(objfile::unlink): Don't call delete.

Change-Id: I6fb7fbf06efb7cb7474c525908365863eae27eb3
This commit is contained in:
Tom Tromey 2019-11-03 14:47:55 -07:00
parent 343cc95202
commit 7d7167ce1b
5 changed files with 123 additions and 17 deletions
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16
gdb/ChangeLog
View File

@ -1,3 +1,19 @@
2019-12-12 Tom Tromey <tom@tromey.com>
* progspace.h (objfile_list): New typedef.
(class unwrapping_objfile_iterator)
(struct unwrapping_objfile_range): Newl
(struct program_space) <objfiles_range>: Change type.
<objfiles>: Change return type.
<add_objfile>: Change type of "objfile" parameter.
<objfiles_list>: Now a list of shared_ptr.
* progspace.c (program_space::add_objfile): Change type of
"objfile". Update.
(program_space::remove_objfile): Update.
* objfiles.h (struct objfile) <~objfile>: Make public.
* objfiles.c (objfile::make): Update.
(objfile::unlink): Don't call delete.
2019-12-12 Tom Tromey <tom@tromey.com>
* symfile.c (symbol_file_clear): Update.

6
gdb/objfiles.c
View File

@ -486,7 +486,10 @@ objfile::make (bfd *bfd_, const char *name_, objfile_flags flags_,
if (parent != nullptr)
add_separate_debug_objfile (result, parent);
current_program_space->add_objfile (result, parent);
/* Using std::make_shared might be a bit nicer here, but that would
require making the constructor public. */
current_program_space->add_objfile (std::shared_ptr<objfile> (result),
parent);
/* Rebuild section map next time we need it. */
get_objfile_pspace_data (current_program_space)->new_objfiles_available = 1;
@ -500,7 +503,6 @@ void
objfile::unlink ()
{
current_program_space->remove_objfile (this);
delete this;
}
/* Free all separate debug objfile of OBJFILE, but don't free OBJFILE

13
gdb/objfiles.h
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@ -28,12 +28,14 @@
#include "registry.h"
#include "gdb_bfd.h"
#include "psymtab.h"
#include <atomic>
#include <bitset>
#include <vector>
#include "gdbsupport/next-iterator.h"
#include "gdbsupport/safe-iterator.h"
#include "bcache.h"
#include "gdbarch.h"
#include "gdbsupport/refcounted-object.h"
struct htab;
struct objfile_data;
@ -399,11 +401,16 @@ private:
/* The only way to create an objfile is to call objfile::make. */
objfile (bfd *, const char *, objfile_flags);
/* The only way to free an objfile is via 'unlink'. */
~objfile ();
public:
/* Normally you should not call delete. Instead, call 'unlink' to
remove it from the program space's list. In some cases, you may
need to hold a reference to an objfile that is independent of its
existence on the program space's list; for this case, the
destructor must be public so that shared_ptr can reference
it. */
~objfile ();
/* Create an objfile. */
static objfile *make (bfd *bfd_, const char *name_, objfile_flags flags_,
objfile *parent = nullptr);

21
gdb/progspace.c
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@ -175,16 +175,20 @@ program_space::free_all_objfiles ()
/* See progspace.h. */
void
program_space::add_objfile (struct objfile *objfile, struct objfile *before)
program_space::add_objfile (std::shared_ptr<objfile> &&objfile,
struct objfile *before)
{
if (before == nullptr)
objfiles_list.push_back (objfile);
objfiles_list.push_back (std::move (objfile));
else
{
auto iter = std::find (objfiles_list.begin (), objfiles_list.end (),
before);
auto iter = std::find_if (objfiles_list.begin (), objfiles_list.end (),
[=] (const std::shared_ptr<::objfile> &objf)
{
return objf.get () == before;
});
gdb_assert (iter != objfiles_list.end ());
objfiles_list.insert (iter, objfile);
objfiles_list.insert (iter, std::move (objfile));
}
}
@ -193,8 +197,11 @@ program_space::add_objfile (struct objfile *objfile, struct objfile *before)
void
program_space::remove_objfile (struct objfile *objfile)
{
auto iter = std::find (objfiles_list.begin (), objfiles_list.end (),
objfile);
auto iter = std::find_if (objfiles_list.begin (), objfiles_list.end (),
[=] (const std::shared_ptr<::objfile> &objf)
{
return objf.get () == objfile;
});
gdb_assert (iter != objfiles_list.end ());
objfiles_list.erase (iter);

84
gdb/progspace.h
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@ -38,6 +38,79 @@ struct address_space;
struct program_space_data;
struct address_space_data;
typedef std::list<std::shared_ptr<objfile>> objfile_list;
/* An iterator that wraps an iterator over std::shared_ptr<objfile>,
and dereferences the returned object. This is useful for iterating
over a list of shared pointers and returning raw pointers -- which
helped avoid touching a lot of code when changing how objfiles are
managed. */
class unwrapping_objfile_iterator
{
public:
typedef unwrapping_objfile_iterator self_type;
typedef typename ::objfile *value_type;
typedef typename ::objfile &reference;
typedef typename ::objfile **pointer;
typedef typename objfile_list::iterator::iterator_category iterator_category;
typedef typename objfile_list::iterator::difference_type difference_type;
unwrapping_objfile_iterator (const objfile_list::iterator &iter)
: m_iter (iter)
{
}
objfile *operator* () const
{
return m_iter->get ();
}
unwrapping_objfile_iterator operator++ ()
{
++m_iter;
return *this;
}
bool operator!= (const unwrapping_objfile_iterator &other) const
{
return m_iter != other.m_iter;
}
private:
/* The underlying iterator. */
objfile_list::iterator m_iter;
};
/* A range that returns unwrapping_objfile_iterators. */
struct unwrapping_objfile_range
{
typedef unwrapping_objfile_iterator iterator;
unwrapping_objfile_range (objfile_list &ol)
: m_list (ol)
{
}
iterator begin () const
{
return iterator (m_list.begin ());
}
iterator end () const
{
return iterator (m_list.end ());
}
private:
objfile_list &m_list;
};
/* A program space represents a symbolic view of an address space.
Roughly speaking, it holds all the data associated with a
non-running-yet program (main executable, main symbols), and when
@ -139,15 +212,15 @@ struct program_space
program_space (address_space *aspace_);
~program_space ();
typedef std::list<struct objfile *> objfiles_range;
typedef unwrapping_objfile_range objfiles_range;
/* Return an iterable object that can be used to iterate over all
objfiles. The basic use is in a foreach, like:
for (objfile *objf : pspace->objfiles ()) { ... } */
objfiles_range &objfiles ()
objfiles_range objfiles ()
{
return objfiles_list;
return unwrapping_objfile_range (objfiles_list);
}
typedef basic_safe_range<objfiles_range> objfiles_safe_range;
@ -167,7 +240,8 @@ struct program_space
/* Add OBJFILE to the list of objfiles, putting it just before
BEFORE. If BEFORE is nullptr, it will go at the end of the
list. */
void add_objfile (struct objfile *objfile, struct objfile *before);
void add_objfile (std::shared_ptr<objfile> &&objfile,
struct objfile *before);
/* Remove OBJFILE from the list of objfiles. */
void remove_objfile (struct objfile *objfile);
@ -234,7 +308,7 @@ struct program_space
struct objfile *symfile_object_file = NULL;
/* All known objfiles are kept in a linked list. */
std::list<struct objfile *> objfiles_list;
std::list<std::shared_ptr<objfile>> objfiles_list;
/* The set of target sections matching the sections mapped into
this program space. Managed by both exec_ops and solib.c. */