On Thu, Aug 17, 2023 at 12:34 AM David Malcolm <dmalc...@redhat.com> wrote:
> On Wed, 2023-08-16 at 14:19 +0200, priour...@gmail.com wrote:
> > From: benjamin priour <vultk...@gcc.gnu.org>
> >
> > Hi,
> > (s/we/the analyzer/)
>
> Hi Benjamin, thanks for the updated patch.
>
> >
> > I've been continuing my patch of supporting operator new variants
> > in the analyzer, and have added a few more test cases.
> >
> >
> > > > If "y" is null then the allocation failed and dereferencing
> > "y" will
> > > > cause
> > > > a segfault, not a "use-of-uninitialized-value".
> > > > Thus we should stick to 'dereference of NULL 'y'" only.
> > > > If "y" is non-null then the allocation succeeded and "*y" is
> > > > initialized
> > > > since we are calling a default initialization with the empty
> > > > parenthesis.
> > >
> > > I *think* it's possible to have the region_model have y
> > pointing to a
> > > heap_allocated_region of sizeof(int) size that's been
> > initialized, but
> > > still have the malloc state machine part of the program_state
> > say that
> > > the pointer is maybe-null.
> >
> > By maybe-null are you implying a new sm-malloc state ?
>
> Sorry, I was too vague here.
>
> I was referring to the "unchecked" state in sm-malloc.cc, which
> represents a pointer that's been returned from an allocator function,
> where the pointer hasn't yet been checked for being null/non-null.
>
> Oh I see then. Unfortunately I don't think initializing the
heap_allocated_region
while having he unchecked state is doable here. I could do it in the
kf_operator_new::on_call_{pre,post} hook, but it's not actually operator
new that
initiliaze the allocated region.
For calls such as "A a = new (nothrow) A;", then 'a' is actually never
initialized,
therefore we need the heap_allocated_region to reflect that.
> > I am not sure to follow on that front.
> >
> >
> > >
> > > > This led me to consider having "null-dereference" supersedes
> > > > "use-of-uninitialized-value", but
> > > > new PR 110830 made me reexamine it.
> > > >
> > > > I believe fixing PR 110830 is thus required before submitting
> > this
> > > > patch,
> > > > or we would have some extra irrelevant warnings.
> > >
> > > How bad would the problem be? PR 110830 looks a little
> > involved, so is
> > > there a way to get the current patch in without dragging that
> > extra
> > > complexity in?
> >
> > Having "null-dereference" supersedes "use-of-uninitialized-value"
> > would
> > cause false negative upon conditional return statement (similarly as
> > demonstrated
> > in PR 110830).
> >
> > Since PR 110830 is off for the moment, I have tried solving this
> > differently.
> > I have considered using known NULL constraints on
> > heap_allocated_region
> > as "initialized_value".
> >
> > You can see below in the diff of region_model::get_store_value
> > two versions of this approach. The version commented out proved to
> > solve
> > the issue of the spurious "use-of-unitialized-value" tagging along
> > calls to
> > "new(std::nothrow) ()". However, this version also shortcircuits the
> > diagnostics of the "null-dereference" warning.
> >
> > Given
> > /* { dg-additional-options "-O0 -fno-exceptions -fno-analyzer-
> > suppress-followups" } */
> > #include <new>
> >
> > struct A
> > {
> > int x;
> > int y;
> > };
> >
> > void test_nonthrowing ()
> > {
> > A* y = new(std::nothrow) A();
> > int z = y->x + 2; /* { dg-warning "dereference of NULL 'y'" }
> > */
> > /* { dg-bogus "use of uninitialized value '\\*y'" "" { xfail *-
> > *-* } .-1 } */
> >
> > delete y;
> > }
> >
> > The analyzer sees gimple
> >
> > <bb 2> :
> > _7 = operator new (8, ¬hrow);
> > if (_7 != 0B)
> > goto <bb 3>; [INV]
> > else
> > goto <bb 4>; [INV]
>
> I would have thought that at each branch of this conditional that
> region_model::add_constraint would be called, and within that we'd
> reach this code:
>
> 4339 /* Notify the context, if any. This exists so that the state
> machines
> 4340 in a program_state can be notified about the condition, and
> so can
> 4341 set sm-state for e.g. unchecked->checked, both for cfg-edges,
> and
> 4342 when synthesizing constraints as above. */
> 4343 if (ctxt)
> 4344 ctxt->on_condition (lhs, op, rhs);
>
> This ought to call impl_region_model_context::on_condition in
> engine.cc, which ought to call malloc_state_machine::on_condition in
> sm-malloc.cc, and this ought to transition the sm-state of _7.
>
> Is something going wrong somewhere in the things I mentioned above?
>
> Nope. Everything's happening as you say.
> >
> > <bb 3> :
> > MEM[(struct A *)_7].x = 0;
> > MEM[(struct A *)_7].y = 0;
> > iftmp.0_11 = _7;
> > goto <bb 5>; [INV]
> >
> > <bb 4> :
> > iftmp.0_8 = _7;
> >
> > <bb 5> :
> > # iftmp.0_2 = PHI <iftmp.0_11(3), iftmp.0_8(4)>
> > y_12 = iftmp.0_2;
> > _1 = y_12->x;
>
> ...and at this point we have a deref from y_12, which on the path from
> bb 5 ought to be an svalue that has the "null" state in the sm-state
> machine, and thus malloc_state_machine::on_stmt ought to complain at
> _1 = y_12->x;
> here:
>
> 2094 else if (state == m_null)
> 2095 {
> 2096 tree diag_arg = sm_ctxt->get_diagnostic_tree
> 2097 sm_ctxt->warn (node, stmt, arg,
> 2098 make_unique<null_deref> (*this,
> diag_arg));
> 2099 sm_ctxt->set_next_state (stmt, arg, m_stop);
> 2100 }
>
> That's what ought to be happening, and ought to give you the correct
> warning.
>
>
> (nods)
>
> > z_13 = _1 + 2;
> > y.1_14 = y_12;
> > if (y.1_14 != 0B)
> > goto <bb 6>; [INV]
> > else
> > goto <bb 7>; [INV]
> >
> > <bb 6> :
> > *y.1_14 ={v} {CLOBBER};
> > operator delete (y.1_14, 8);
> >
> > The injurious path, causing the "use-of-uninit" warning is as
> > follows:
> > <bb 2> :
> > _7 = operator new (8, ¬hrow);
> > if (_7 != 0B)
> > ...
> > else <- Takes false branch
> > goto <bb 4>; [INV]
> >
> > ...
> >
> > <bb 4> :
> > iftmp.0_8 = _7; <- MEM[(struct A*) _7] is left uninit in this bb
> >
> > <bb 5> :
> > # iftmp.0_2 = PHI <iftmp.0_11(3), iftmp.0_8(4)> <- iftmp.0_2 =
> > iftmp.0_8(4)
> > y_12 = iftmp.0_2;
> > _1 = y_12->x; // deref of null y_12, use of uninit y_12->x
> > z_13 = _1 + 2; // check_for_poison sets _1 to unknown_svalue
> > y.1_14 = y_12;
> > if (y.1_14 != 0B)
> > goto <bb 6>; [INV]
> > else
> > goto <bb 7>; [INV]
> >
> > Then using the "commented-out" fix, iftmp.0_8 which had an uninit
> > value is
>
> Sorry, I'm not sure what you mean by the '"commented-out" fix' here.
>
>
First attempt (I agree the comment block wasn't the most noticeable thing
amidst the diff).
Check for constraints when the region was found with bindings.
@@ -2321,6 +2334,16 @@ region_model::get_store_value (const region
*reg,
= m_store.get_any_binding (m_mgr->get_store_manager (), reg);
if (sval)
{
+ if (m_constraints->sval_constrained_p (sval))
+ {
+ equiv_class_id sval_ecid = equiv_class_id::null ();
+ if (m_constraints->get_equiv_class_by_svalue (sval,
&sval_ecid))
+ {
+ const equiv_class& sval_ec =
sval_ecid.get_obj(*m_constraints);
+ if (sval_ec.get_any_constant () != NULL_TREE)
+ sval = sval_ec.m_cst_sval;
+ }
+ }
if (reg->get_type ())
sval = m_mgr->get_or_create_cast (reg->get_type (), sval);
return sval;
Second attempt in get_store_value, check for constraints right before the
final return statement.
@@ -2363,6 +2386,28 @@ region_model::get_store_value (const region
*reg,
== RK_GLOBALS)
return get_initial_value_for_global (reg);
+ /* If there exists a NULL constraint on the parent region,
+ then do not create a poisoned_uninit value. */
+ if (reg->get_kind () == RK_FIELD || reg->get_kind () ==
RK_ELEMENT)
+ {
+ const region *base_reg = reg->get_base_region ();
+ const svalue *base_sval
+ = m_store.get_any_binding (m_mgr->get_store_manager (),
base_reg);
+ if (base_sval)
+ {
+ if (m_constraints->sval_constrained_p (base_sval))
+ {
+ equiv_class_id sval_ecid = equiv_class_id::null ();
+ if (m_constraints->get_equiv_class_by_svalue
(base_sval, &sval_ecid))
+ {
+ const equiv_class& sval_ec =
sval_ecid.get_obj(*m_constraints);
+ if (const_tree cst = sval_ec.get_any_constant ())
+ if (::zerop (cst))
+ check_poisoned = false;
+ }
+ }
+ }
+ }
return m_mgr->get_or_create_initial_value (reg, check_poisoned);
}
> forcibly set to constant_svalue(0), since the analyzer detects a NULL
> > constraint
> > on &heap_allocated_region.
> > Unfortunately, this loses all clusters binding on _7 and the
> > followings
> > variables, such as when we arrive at "_1 = y_12->x", we emit a
> > "null_deref" not because the heap_allocated_region is in a null
> > state,
> > but because we are dereferencing a constant "0".
> > Thus the analysis path no longer tracks down the creation of this
> > region, and the genese event is "iftmp.0_8 = _7".
>
> It sounds like you are getting a null_deref on the pointer, which
> sounds correct.
>
> If we've dereferenced a null pointer, we should probably terminate the
> path, which would stop the follow-up warnings about uninitialized
> fields; the initializations were skipped anyway (by going to bb 4,
> rather than bb 3).
>
> We both agree on that. The issue is that the (first) poisoned diagnostic
is emitted during the processing of region_model::on_stmt_pre, into
region_model::on_assignment, into region_model::get_gassign_result
, whereas the null_deref is emitted by sm_malloc::on_stmt.
exploded_node::on_stmt
| exploded_node::on_stmt_pre
| region_model::on_stmt_pre
| region_model:::on assignment
| region_model::get_gassign_result -> calls get_rvalue that emits
poisoned_value diagnostic
| sm-malloc.on_stmt [/* Handle dereference, state == m_null */] -> emits
null_deref diagnostic
| terminate_path
The null_deref diagnostic does actually terminate the path, but too late
to prevent the first poisoned_diagnostic, already saved.
That's why I'm trying to get information out of the constraints, that *are*
correctly applied
by the prior on_condition, so that I can nip the poisoned_diagnostic
without relying on sm-malloc,
which happens too late.
Thanks,
Benjamin.
> Does this help?
> Dave
>
> >
> > As you guess, this loss of information fails a lot of regression
> > tests,
> > although it achieves the goal of removing the "use-of-uninit"
> > warning.
> >
> > The second attempt (see get_store_value diff below, the non-commented
> > out block), actually does nothing, which as I understood through
> > debugging was to be expected. We are doing the same "constraints"
> > check
> > as the former version, but only as a last resort before resorting to
> > creating an initial or unknown svalue.
> > And instead of creating a constant_svalue(0) as before, now a NULL
> > constraint only prevents the creation of a poisoned_svalue(uninit)
> > by setting "check_poisoned" to false.
> >
> > However in
> > + if (reg->get_kind () == RK_FIELD || reg->get_kind () ==
> > RK_ELEMENT)
> > + {
> > + const region *base_reg = reg->get_base_region ();
> > + const svalue *base_sval
> > + = m_store.get_any_binding (m_mgr->get_store_manager (),
> > base_reg);
> > + if (base_sval)
> > + {
> > + ...
> > + }
> >
> > base_sval is always NULL (which makes sense since otherwise we
> > wouldn't
> > need to create an initial_svalue).
> >
> > The spirit behind this second attempt is to not lose any sort of
> > information, therefore to not forcibly create constant_svalues.
> >
> > Thus, instead of assigning a null_svalue at "iftmp.0_8 = _7",
> > rather wait for the latest "_1 = y_12->x;" and prevent the creation
> > of a "poisoned_svalue (uninit)".
> >
> > The failings of the second attempt is to find the NULL constraint of
> > the heap_allocated_region (which still exists thanks to path
> > splitting)
> > given the COMPONENT_REF y_12->x;
> >
> > I am unsure as to how to do that, thus this RFC.
> >
> >
> > Thanks,
> > Benjamin.
> > Patch below.
> > ---
> >
> > Fixed spurious possibly-NULL warning always tagging along throwing
> > operator new despite it never returning NULL.
> > Now, operator new is correctly recognized as possibly returning
> > NULL if and only if it is non-throwing or exceptions have been
> > disabled.
> > Different standard signatures of operator new are now properly
> > recognized.
> >
> > Added support of placement new, so that is now properly recognized,
> > and a 'heap_allocated' region is no longer created for it.
> > Placement new size is also checked and a 'Wanalyzer-allocation-size'
> > is emitted when relevant, as well as always a 'Wanalyzer-out-of-
> > bounds'.
> >
> > 'operator new' nothrow variants are detected by checking the types
> > of the parameters.
> > Indeed, in a call to new (std::nothrow) (), although the chosen
> > overload
> > has signature 'operator new (void*, std::nothrow_t&)', where
> > parameter 1
> > is a reference. In a placement new, parameter 1 will always be a
> > [void]
> > pointer.
> >
> > Prior to this patch, some buffers allocated with 'new',
> > then deleted and thereafter used would result in a
> > Wanalyzer-use-after-free warning. However,
> > the wording was "use after 'free' of" instead of the expected
> > "use after 'delete' of".
> >
> > This patch fixed this by introducing a new kind of
> > poisoned value.
> >
> > Signed-off-by: benjamin priour <vultk...@gcc.gnu.org>
> >
> > gcc/analyzer/ChangeLog:
> >
> > * analyzer.h (is_placement_new_p): New declaration.
> > * call-details.cc
> > (call_details::maybe_get_arg_region): New function.
> > Returns the region of the argument at given index if
> > possible.
> > * call-details.h: Declaration of the above function.
> > * kf-lang-cp.cc (is_placement_new_p): Returns true if the
> > gcall is recognized as a placement new.
> > (kf_operator_delete::impl_call_post): Unbinding a region and
> > its
> > descendent now poisons with POISON_KIND_DELETED.
> > (register_known_functions_lang_cp): Known function "operator
> > delete"
> > is now registered only once independently of its number of
> > parameters.
> > * region-model.cc (region_model::get_rvalue_1):
> > (region_model::get_store_value): Attempt to use a region
> > NULL constraint to emit a null_ptr_svalue instead of an
> > uninit
> > poisoned_svalue.
> > (region_model::eval_condition):
> > Now recursively calls itself if any of the operand is wrapped
> > in a cast.
> > * sm-malloc.cc (malloc_state_machine::on_stmt):
> > Add placement new recognition.
> > * svalue.cc (poison_kind_to_str): Wording for the new PK.
> > * svalue.h (enum poison_kind): Add value POISON_KIND_DELETED.
> >
> > gcc/testsuite/ChangeLog:
> >
> > * g++.dg/analyzer/out-of-bounds-placement-new.C: Added a
> > directive.
> > * g++.dg/analyzer/placement-new.C: Added tests.
> > * g++.dg/analyzer/new-2.C: New test.
> > * g++.dg/analyzer/noexcept-new.C: New test.
> > * g++.dg/analyzer/placement-new-size.C: New test.
> > ---
> > gcc/analyzer/analyzer.h | 1 +
> > gcc/analyzer/call-details.cc | 11 ++
> > gcc/analyzer/call-details.h | 1 +
> > gcc/analyzer/kf-lang-cp.cc | 111 +++++++++++++++-
> > --
> > gcc/analyzer/region-model.cc | 68 ++++++++++-
> > gcc/analyzer/sm-malloc.cc | 17 ++-
> > gcc/analyzer/svalue.cc | 2 +
> > gcc/analyzer/svalue.h | 3 +
> > gcc/testsuite/g++.dg/analyzer/new-2.C | 70 +++++++++++
> > gcc/testsuite/g++.dg/analyzer/noexcept-new.C | 48 ++++++++
> > .../analyzer/out-of-bounds-placement-new.C | 2 +-
> > .../g++.dg/analyzer/placement-new-size.C | 27 +++++
> > gcc/testsuite/g++.dg/analyzer/placement-new.C | 92 ++++++++++++++-
> > 13 files changed, 427 insertions(+), 26 deletions(-)
> > create mode 100644 gcc/testsuite/g++.dg/analyzer/new-2.C
> > create mode 100644 gcc/testsuite/g++.dg/analyzer/noexcept-new.C
> > create mode 100644 gcc/testsuite/g++.dg/analyzer/placement-new-
> > size.C
> >
> > diff --git a/gcc/analyzer/analyzer.h b/gcc/analyzer/analyzer.h
> > index 93a28b4b5cf..f44e8296f5e 100644
> > --- a/gcc/analyzer/analyzer.h
> > +++ b/gcc/analyzer/analyzer.h
> > @@ -401,6 +401,7 @@ extern bool is_std_named_call_p (const_tree
> > fndecl, const char *funcname,
> > const gcall *call, unsigned int
> > num_args);
> > extern bool is_setjmp_call_p (const gcall *call);
> > extern bool is_longjmp_call_p (const gcall *call);
> > +extern bool is_placement_new_p (const gcall *call);
> >
> > extern const char *get_user_facing_name (const gcall *call);
> >
> > diff --git a/gcc/analyzer/call-details.cc b/gcc/analyzer/call-
> > details.cc
> > index fa86f55177a..0ac44f3726c 100644
> > --- a/gcc/analyzer/call-details.cc
> > +++ b/gcc/analyzer/call-details.cc
> > @@ -283,6 +283,17 @@ call_details::get_arg_svalue (unsigned idx)
> > const
> > return m_model->get_rvalue (arg, m_ctxt);
> > }
> >
> > +/* If argument IDX's svalue at the callsite is a region_svalue,
> > + return the region it points to.
> > + Otherwise return NULL. */
> > +
> > +const region *
> > +call_details::maybe_get_arg_region (unsigned idx) const
> > +{
> > + const svalue *sval = get_arg_svalue (idx);
> > + return sval->maybe_get_region ();
> > +}
> > +
> > /* Attempt to get the string literal for argument IDX, or return
> > NULL
> > otherwise.
> > For use when implementing "__analyzer_*" functions that take
> > diff --git a/gcc/analyzer/call-details.h b/gcc/analyzer/call-
> > details.h
> > index 0622cab7856..919338f88b9 100644
> > --- a/gcc/analyzer/call-details.h
> > +++ b/gcc/analyzer/call-details.h
> > @@ -60,6 +60,7 @@ public:
> > tree get_arg_tree (unsigned idx) const;
> > tree get_arg_type (unsigned idx) const;
> > const svalue *get_arg_svalue (unsigned idx) const;
> > + const region *maybe_get_arg_region (unsigned idx) const;
> > const char *get_arg_string_literal (unsigned idx) const;
> >
> > tree get_fndecl_for_call () const;
> > diff --git a/gcc/analyzer/kf-lang-cp.cc b/gcc/analyzer/kf-lang-cp.cc
> > index 393b4f25e79..cfb0584979b 100644
> > --- a/gcc/analyzer/kf-lang-cp.cc
> > +++ b/gcc/analyzer/kf-lang-cp.cc
> > @@ -35,6 +35,38 @@ along with GCC; see the file COPYING3. If not see
> >
> > #if ENABLE_ANALYZER
> >
> > +/* Return true if CALL is a non-allocating operator new or operator
> > new []
> > + that contains no user-defined args, i.e. having any signature of:
> > +
> > + - void* operator new (std::size_t count, void* ptr);
> > + - void* operator new[] (std::size_t count, void* ptr);
> > +
> > + See https://en.cppreference.com/w/cpp/memory/new/operator_new. */
> > +
> > +bool is_placement_new_p (const gcall *call)
> > +{
> > + gcc_assert (call);
> > + tree fndecl = gimple_call_fndecl (call);
> > +
> > + if (!fndecl || TREE_CODE (TREE_TYPE (fndecl)) == METHOD_TYPE)
> > + /* Give up on overloaded operator new. */
> > + return false;
> > +
> > + if (!is_named_call_p (fndecl, "operator new", call, 2)
> > + && !is_named_call_p (fndecl, "operator new []", call, 2))
> > + return false;
> > +
> > + /* We must distinguish between an allocating non-throwing new
> > + and a non-allocating new.
> > +
> > + The former might have one of the following signatures :
> > + void* operator new (std::size_t count, const std::nothrow_t&
> > tag);
> > + void* operator new[] (std::size_t count, const std::nothrow_t&
> > tag);
> > + Whereas a placement new would take a pointer. */
> > + tree arg1_type = TREE_CHAIN (TYPE_ARG_TYPES (TREE_TYPE (fndecl)));
> > + return TREE_CODE (TREE_VALUE (arg1_type)) == POINTER_TYPE;
> > +}
> > +
> > namespace ana {
> >
> > /* Implementations of specific functions. */
> > @@ -46,7 +78,11 @@ class kf_operator_new : public known_function
> > public:
> > bool matches_call_types_p (const call_details &cd) const final
> > override
> > {
> > - return cd.num_args () == 1;
> > + return (cd.num_args () == 1
> > + && cd.arg_is_size_p (0))
> > + || (cd.num_args () == 2
> > + && cd.arg_is_size_p (0)
> > + && POINTER_TYPE_P (cd.get_arg_type (1)));
> > }
> >
> > void impl_call_pre (const call_details &cd) const final override
> > @@ -54,28 +90,74 @@ public:
> > region_model *model = cd.get_model ();
> > region_model_manager *mgr = cd.get_manager ();
> > const svalue *size_sval = cd.get_arg_svalue (0);
> > - const region *new_reg
> > - = model->get_or_create_region_for_heap_alloc (size_sval,
> > cd.get_ctxt ());
> > - if (cd.get_lhs_type ())
> > + region_model_context *ctxt = cd.get_ctxt ();
> > + const gcall *call = cd.get_call_stmt ();
> > +
> > + /* If the call was actually a placement new, check that
> > accessing
> > + the buffer lhs is placed into does not result in out-of-
> > bounds. */
> > + if (is_placement_new_p (call))
> > {
> > + const region *ptr_reg = cd.maybe_get_arg_region (1);
> > + if (ptr_reg && cd.get_lhs_type ())
> > + {
> > + const region *base_reg = ptr_reg->get_base_region ();
> > + const svalue *num_bytes_sval = cd.get_arg_svalue (0);
> > + const region *sized_new_reg = mgr->get_sized_region
> > (base_reg,
> > + cd.get_lhs_type (),
> > + num_bytes_sval);
> > + model->check_region_for_write (sized_new_reg,
> > + nullptr,
> > + ctxt);
> > const svalue *ptr_sval
> > - = mgr->get_ptr_svalue (cd.get_lhs_type (), new_reg);
> > + = mgr->get_ptr_svalue (cd.get_lhs_type (), sized_new_reg);
> > cd.maybe_set_lhs (ptr_sval);
> > + }
> > + }
> > + /* If the call is an allocating new, then create a heap
> > allocated
> > + region. */
> > + else
> > + {
> > + const region *new_reg
> > + = model->get_or_create_region_for_heap_alloc (size_sval,
> > ctxt);
> > + if (cd.get_lhs_type ())
> > + {
> > + const svalue *ptr_sval
> > + = mgr->get_ptr_svalue (cd.get_lhs_type (), new_reg);
> > + cd.maybe_set_lhs (ptr_sval);
> > + }
> > + }
> > + }
> > +
> > + void impl_call_post (const call_details &cd) const final override
> > + {
> > + region_model *model = cd.get_model ();
> > + region_model_manager *mgr = cd.get_manager ();
> > + tree callee_fndecl = cd.get_fndecl_for_call ();
> > + region_model_context *ctxt = cd.get_ctxt ();
> > +
> > + /* If the call is guaranteed to return nonnull
> > + then add a nonnull constraint to the allocated region. */
> > + if (!TREE_NOTHROW (callee_fndecl) && flag_exceptions)
> > + {
> > + const svalue *null_sval
> > + = mgr->get_or_create_null_ptr (cd.get_lhs_type ());
> > + const svalue *result
> > + = model->get_store_value (cd.get_lhs_region (), ctxt);
> > + model->add_constraint (result, NE_EXPR, null_sval, ctxt);
> > }
> > }
> > };
> >
> > -/* Handler for "operator delete", both the sized and unsized
> > variants
> > - (2 arguments and 1 argument respectively), and for "operator
> > delete []" */
> > +/* Handler for "operator delete" and for "operator delete []",
> > + both the sized and unsized variants
> > + (2 arguments and 1 argument respectively). */
> >
> > class kf_operator_delete : public known_function
> > {
> > public:
> > - kf_operator_delete (unsigned num_args) : m_num_args (num_args) {}
> > -
> > bool matches_call_types_p (const call_details &cd) const final
> > override
> > {
> > - return cd.num_args () == m_num_args;
> > + return cd.num_args () == 1 or cd.num_args () == 2;
> > }
> >
> > void impl_call_post (const call_details &cd) const final override
> > @@ -86,12 +168,10 @@ public:
> > {
> > /* If the ptr points to an underlying heap region, delete it,
> > poisoning pointers. */
> > - model->unbind_region_and_descendents (freed_reg,
> > POISON_KIND_FREED);
> > + model->unbind_region_and_descendents (freed_reg,
> > POISON_KIND_DELETED);
> > }
> > }
> >
> > -private:
> > - unsigned m_num_args;
> > };
> >
> > /* Populate KFM with instances of known functions relating to C++.
> > */
> > @@ -101,9 +181,8 @@ register_known_functions_lang_cp
> > (known_function_manager &kfm)
> > {
> > kfm.add ("operator new", make_unique<kf_operator_new> ());
> > kfm.add ("operator new []", make_unique<kf_operator_new> ());
> > - kfm.add ("operator delete", make_unique<kf_operator_delete> (1));
> > - kfm.add ("operator delete", make_unique<kf_operator_delete> (2));
> > - kfm.add ("operator delete []", make_unique<kf_operator_delete>
> > (1));
> > + kfm.add ("operator delete", make_unique<kf_operator_delete> ());
> > + kfm.add ("operator delete []", make_unique<kf_operator_delete>
> > ());
> > }
> >
> > } // namespace ana
> > diff --git a/gcc/analyzer/region-model.cc b/gcc/analyzer/region-
> > model.cc
> > index 494a9cdf149..a358794356e 100644
> > --- a/gcc/analyzer/region-model.cc
> > +++ b/gcc/analyzer/region-model.cc
> > @@ -499,6 +499,7 @@ public:
> > case POISON_KIND_UNINIT:
> > return OPT_Wanalyzer_use_of_uninitialized_value;
> > case POISON_KIND_FREED:
> > + case POISON_KIND_DELETED:
> > return OPT_Wanalyzer_use_after_free;
> > case POISON_KIND_POPPED_STACK:
> > return OPT_Wanalyzer_use_of_pointer_in_stale_stack_frame;
> > @@ -531,6 +532,15 @@ public:
> > m_expr);
> > }
> > break;
> > + case POISON_KIND_DELETED:
> > + {
> > + diagnostic_metadata m;
> > + m.add_cwe (416); /* "CWE-416: Use After Free". */
> > + return warning_meta (rich_loc, m, get_controlling_option
> > (),
> > + "use after %<delete%> of %qE",
> > + m_expr);
> > + }
> > + break;
> > case POISON_KIND_POPPED_STACK:
> > {
> > /* TODO: which CWE? */
> > @@ -555,6 +565,9 @@ public:
> > case POISON_KIND_FREED:
> > return ev.formatted_print ("use after %<free%> of %qE here",
> > m_expr);
> > + case POISON_KIND_DELETED:
> > + return ev.formatted_print ("use after %<delete%> of %qE
> > here",
> > + m_expr);
> > case POISON_KIND_POPPED_STACK:
> > return ev.formatted_print
> > ("dereferencing pointer %qE to within stale stack frame",
> > @@ -2210,7 +2223,7 @@ region_model::get_rvalue_1 (path_var pv,
> > region_model_context *ctxt) const
> > case MEM_REF:
> > {
> > const region *ref_reg = get_lvalue (pv, ctxt);
> > - return get_store_value (ref_reg, ctxt);
> > + return get_store_value (ref_reg, ctxt); // INFO get store
> > value of field_region(cast_region(heap_allocated_region(19), ‘struct
> > A’), ‘int’, ‘int A::x’)
> > }
> > case OBJ_TYPE_REF:
> > {
> > @@ -2321,6 +2334,16 @@ region_model::get_store_value (const region
> > *reg,
> > = m_store.get_any_binding (m_mgr->get_store_manager (), reg);
> > if (sval)
> > {
> > +/* if (m_constraints->sval_constrained_p (sval))
> > + {
> > + equiv_class_id sval_ecid = equiv_class_id::null ();
> > + if (m_constraints->get_equiv_class_by_svalue (sval,
> > &sval_ecid))
> > + {
> > + const equiv_class& sval_ec =
> > sval_ecid.get_obj(*m_constraints);
> > + if (sval_ec.get_any_constant () != NULL_TREE)
> > + sval = sval_ec.m_cst_sval;
> > + }
> > + } */
> > if (reg->get_type ())
> > sval = m_mgr->get_or_create_cast (reg->get_type (), sval);
> > return sval;
> > @@ -2363,6 +2386,28 @@ region_model::get_store_value (const region
> > *reg,
> > == RK_GLOBALS)
> > return get_initial_value_for_global (reg);
> >
> > + /* If there exists a NULL constraint on the parent region,
> > + then do not create a poisoned_uninit value. */
> > + if (reg->get_kind () == RK_FIELD || reg->get_kind () ==
> > RK_ELEMENT)
> > + {
> > + const region *base_reg = reg->get_base_region ();
> > + const svalue *base_sval
> > + = m_store.get_any_binding (m_mgr->get_store_manager (),
> > base_reg);
> > + if (base_sval)
> > + {
> > + if (m_constraints->sval_constrained_p (base_sval))
> > + {
> > + equiv_class_id sval_ecid = equiv_class_id::null ();
> > + if (m_constraints->get_equiv_class_by_svalue
> > (base_sval, &sval_ecid))
> > + {
> > + const equiv_class& sval_ec =
> > sval_ecid.get_obj(*m_constraints);
> > + if (const_tree cst = sval_ec.get_any_constant ())
> > + if (::zerop (cst))
> > + check_poisoned = false;
> > + }
> > + }
> > + }
> > + }
> > return m_mgr->get_or_create_initial_value (reg, check_poisoned);
> > }
> >
> > @@ -3582,6 +3627,27 @@ region_model::eval_condition (const svalue
> > *lhs,
> > }
> > }
> >
> > + /* Attempt to unwrap cast if there is one, and the types match.
> > */
> > + tree lhs_type = lhs->get_type ();
> > + tree rhs_type = rhs->get_type ();
> > + if (lhs_type && rhs_type)
> > + {
> > + const unaryop_svalue *lhs_un_op = dyn_cast <const unaryop_svalue
> > *> (lhs);
> > + const unaryop_svalue *rhs_un_op = dyn_cast <const unaryop_svalue
> > *> (rhs);
> > + if (lhs_un_op && CONVERT_EXPR_CODE_P (lhs_un_op->get_op ())
> > + && rhs_un_op && CONVERT_EXPR_CODE_P (rhs_un_op->get_op ())
> > + && lhs_type == rhs_type)
> > + return eval_condition (lhs_un_op->get_arg (), op, rhs_un_op-
> > >get_arg ());
> > +
> > + else if (lhs_un_op && CONVERT_EXPR_CODE_P (lhs_un_op->get_op ())
> > + && lhs_type == rhs_type)
> > + return eval_condition (lhs_un_op->get_arg (), op, rhs);
> > +
> > + else if (rhs_un_op && CONVERT_EXPR_CODE_P (rhs_un_op->get_op ())
> > + && lhs_type == rhs_type)
> > + return eval_condition (lhs, op, rhs_un_op->get_arg ());
> > + }
> > +
> > /* Otherwise, try constraints.
> > Cast to const to ensure we don't change the constraint_manager
> > as we
> > do this (e.g. by creating equivalence classes). */
> > diff --git a/gcc/analyzer/sm-malloc.cc b/gcc/analyzer/sm-malloc.cc
> > index ec763254b29..567237cf1ae 100644
> > --- a/gcc/analyzer/sm-malloc.cc
> > +++ b/gcc/analyzer/sm-malloc.cc
> > @@ -759,7 +759,7 @@ public:
> > override
> > {
> > if (change.m_old_state == m_sm.get_start_state ()
> > - && unchecked_p (change.m_new_state))
> > + && (unchecked_p (change.m_new_state) || nonnull_p
> > (change.m_new_state)))
> > // TODO: verify that it's the allocation stmt, not a copy
> > return label_text::borrow ("allocated here");
> > if (unchecked_p (change.m_old_state)
> > @@ -1915,11 +1915,16 @@ malloc_state_machine::on_stmt (sm_context
> > *sm_ctxt,
> > return true;
> > }
> >
> > - if (is_named_call_p (callee_fndecl, "operator new", call, 1))
> > - on_allocator_call (sm_ctxt, call, &m_scalar_delete);
> > - else if (is_named_call_p (callee_fndecl, "operator new []",
> > call, 1))
> > - on_allocator_call (sm_ctxt, call, &m_vector_delete);
> > - else if (is_named_call_p (callee_fndecl, "operator delete",
> > call, 1)
> > + if (!is_placement_new_p (call))
> > + {
> > + bool returns_nonnull = !TREE_NOTHROW (callee_fndecl) &&
> > flag_exceptions;
> > + if (is_named_call_p (callee_fndecl, "operator new"))
> > + on_allocator_call (sm_ctxt, call, &m_scalar_delete,
> > returns_nonnull);
> > + else if (is_named_call_p (callee_fndecl, "operator new
> > []"))
> > + on_allocator_call (sm_ctxt, call, &m_vector_delete,
> > returns_nonnull);
> > + }
> > +
> > + if (is_named_call_p (callee_fndecl, "operator delete", call,
> > 1)
> > || is_named_call_p (callee_fndecl, "operator
> > delete", call, 2))
> > {
> > on_deallocator_call (sm_ctxt, node, call,
> > diff --git a/gcc/analyzer/svalue.cc b/gcc/analyzer/svalue.cc
> > index 064627f3dcc..35eb8307b20 100644
> > --- a/gcc/analyzer/svalue.cc
> > +++ b/gcc/analyzer/svalue.cc
> > @@ -970,6 +970,8 @@ poison_kind_to_str (enum poison_kind kind)
> > return "uninit";
> > case POISON_KIND_FREED:
> > return "freed";
> > + case POISON_KIND_DELETED:
> > + return "deleted";
> > case POISON_KIND_POPPED_STACK:
> > return "popped stack";
> > }
> > diff --git a/gcc/analyzer/svalue.h b/gcc/analyzer/svalue.h
> > index 5492b1e0b7c..263a0d7af6f 100644
> > --- a/gcc/analyzer/svalue.h
> > +++ b/gcc/analyzer/svalue.h
> > @@ -350,6 +350,9 @@ enum poison_kind
> > /* For use to describe freed memory. */
> > POISON_KIND_FREED,
> >
> > + /* For use to describe deleted memory. */
> > + POISON_KIND_DELETED,
> > +
> > /* For use on pointers to regions within popped stack frames. */
> > POISON_KIND_POPPED_STACK
> > };
> > diff --git a/gcc/testsuite/g++.dg/analyzer/new-2.C
> > b/gcc/testsuite/g++.dg/analyzer/new-2.C
> > new file mode 100644
> > index 00000000000..9e0315b3f44
> > --- /dev/null
> > +++ b/gcc/testsuite/g++.dg/analyzer/new-2.C
> > @@ -0,0 +1,70 @@
> > +// { dg-additional-options "-O0 -fno-analyzer-suppress-followups -
> > fexceptions" }
> > +#include <new>
> > +
> > +struct A
> > +{
> > + int x;
> > + int y;
> > +};
> > +
> > +void test_spurious_null_warning_throwing ()
> > +{
> > + int *x = new int; /* { dg-bogus "dereference of possibly-NULL" }
> > */
> > + int *y = new int (); /* { dg-bogus "dereference of possibly-NULL"
> > "non-throwing" } */
> > + int *arr = new int[3]; /* { dg-bogus "dereference of possibly-
> > NULL" } */
> > + A *a = new A (); /* { dg-bogus "dereference of possibly-NULL"
> > "throwing new cannot be null" } */
> > +
> > + int z = *y + 2;
> > + z = *x + 4; /* { dg-bogus "dereference of possibly-NULL 'x'" } */
> > + /* { dg-warning "use of uninitialized value '\\*x'" "" { target *-
> > *-* } .-1 } */
> > + z = arr[0] + 4; /* { dg-bogus "dereference of possibly-NULL" } */
> > + /* { dg-warning "use of uninitialized value '\\*arr'" "" { target
> > *-*-* } .-1 } */
> > +
> > + delete a;
> > + delete y;
> > + delete x;
> > + delete[] arr;
> > +}
> > +
> > +void test_default_initialization ()
> > +{
> > + int *y = ::new int;
> > + int *x = ::new int (); /* { dg-bogus "dereference of possibly-
> > NULL 'operator new" } */
> > +
> > + int b = *x + 3; /* { dg-bogus "dereference of possibly-NULL" }
> > */
> > + /* { dg-bogus "use of uninitialized ‘*x’" "" { target *-*-* } .-
> > 1 } */
> > + int a = *y + 2; /* { dg-bogus "dereference of possibly-NULL 'y'"
> > } */
> > + /* { dg-warning "use of uninitialized value '\\*y'" "no default
> > init" { target *-*-* } .-1 } */
> > +
> > + delete x;
> > + delete y;
> > +}
> > +
> > +/* From clang core.uninitialized.NewArraySize
> > +new[] should not be called with an undefined size argument */
> > +
> > +void test_garbage_new_array ()
> > +{
> > + int n;
> > + int *arr = ::new int[n]; /* { dg-warning "use of uninitialized
> > value 'n'" } */
> > + arr[0] = 7;
> > + ::delete[] arr; /* no warnings emitted here either */
> > +}
> > +
> > +void test_nonthrowing ()
> > +{
> > + int* x = new(std::nothrow) int;
> > + int* y = new(std::nothrow) int();
> > + int* arr = new(std::nothrow) int[10];
> > +
> > + int z = *y + 2; /* { dg-warning "dereference of NULL 'y'" } */
> > + /* { dg-bogus "use of uninitialized value '\\*y'" "" { xfail *-*-*
> > } .-1 } */
> > + z = *x + 4; /* { dg-warning "dereference of possibly-NULL 'x'" }
> > */
> > + /* { dg-warning "use of uninitialized value '\\*x'" "" { target *-
> > *-* } .-1 } */
> > + z = arr[0] + 4; /* { dg-warning "dereference of possibly-NULL
> > 'arr'" } */
> > + /* { dg-warning "use of uninitialized value '\\*arr'" "" { target
> > *-*-* } .-1 } */
> > +
> > + delete y;
> > + delete x;
> > + delete[] arr;
> > +}
> > diff --git a/gcc/testsuite/g++.dg/analyzer/noexcept-new.C
> > b/gcc/testsuite/g++.dg/analyzer/noexcept-new.C
> > new file mode 100644
> > index 00000000000..4a5f526b0f3
> > --- /dev/null
> > +++ b/gcc/testsuite/g++.dg/analyzer/noexcept-new.C
> > @@ -0,0 +1,48 @@
> > +/* { dg-additional-options "-O0 -fno-exceptions -fno-analyzer-
> > suppress-followups" } */
> > +#include <new>
> > +
> > +/* Test non-throwing variants of operator new */
> > +
> > +struct A
> > +{
> > + int x;
> > + int y;
> > +};
> > +
> > +void test_throwing ()
> > +{
> > + int* x = new int;
> > + int* y = new int(); /* { dg-warning "dereference of possibly-NULL"
> > } */
> > + int* arr = new int[10];
> > + A *a = new A(); /* { dg-warning "dereference of possibly-NULL" }
> > */
> > +
> > + int z = *y + 2;
> > + z = *x + 4; /* { dg-warning "dereference of possibly-NULL 'x'" }
> > */
> > + /* { dg-warning "use of uninitialized value '\\*x'" "" { target *-
> > *-* } .-1 } */
> > + z = arr[0] + 4; /* { dg-warning "dereference of possibly-NULL
> > 'arr'" } */
> > + /* { dg-warning "use of uninitialized value '\\*arr'" "" { target
> > *-*-* } .-1 } */
> > + a->y = a->x + 3;
> > +
> > + delete a;
> > + delete y;
> > + delete x;
> > + delete[] arr;
> > +}
> > +
> > +void test_nonthrowing ()
> > +{
> > + int* x = new(std::nothrow) int;
> > + int* y = new(std::nothrow) int();
> > + int* arr = new(std::nothrow) int[10];
> > +
> > + int z = *y + 2; /* { dg-warning "dereference of NULL 'y'" } */
> > + /* { dg-bogus "use of uninitialized value '\\*y'" "" { xfail *-*-*
> > } .-1 } */
> > + z = *x + 4; /* { dg-warning "dereference of possibly-NULL 'x'" }
> > */
> > + /* { dg-warning "use of uninitialized value '\\*x'" "" { target *-
> > *-* } .-1 } */
> > + z = arr[0] + 4; /* { dg-warning "dereference of possibly-NULL
> > 'arr'" } */
> > + /* { dg-warning "use of uninitialized value '\\*arr'" "" { target
> > *-*-* } .-1 } */
> > +
> > + delete y;
> > + delete x;
> > + delete[] arr;
> > +}
> > diff --git a/gcc/testsuite/g++.dg/analyzer/out-of-bounds-placement-
> > new.C b/gcc/testsuite/g++.dg/analyzer/out-of-bounds-placement-new.C
> > index d3076c3cf25..33872e6ddab 100644
> > --- a/gcc/testsuite/g++.dg/analyzer/out-of-bounds-placement-new.C
> > +++ b/gcc/testsuite/g++.dg/analyzer/out-of-bounds-placement-new.C
> > @@ -14,6 +14,6 @@ struct int_and_addr {
> >
> > int test (int_container ic)
> > {
> > - int_and_addr *iaddr = new (ic.addr ()) int_and_addr;
> > + int_and_addr *iaddr = new (ic.addr ()) int_and_addr; /* { dg-
> > warning "stack-based buffer overflow" } */
> > return iaddr->i;
> > }
> > diff --git a/gcc/testsuite/g++.dg/analyzer/placement-new-size.C
> > b/gcc/testsuite/g++.dg/analyzer/placement-new-size.C
> > new file mode 100644
> > index 00000000000..4536d361b4a
> > --- /dev/null
> > +++ b/gcc/testsuite/g++.dg/analyzer/placement-new-size.C
> > @@ -0,0 +1,27 @@
> > +/* { dg-additional-options "-Wno-placement-new -Wno-analyzer-use-of-
> > uninitialized-value" } */
> > +
> > +#include <new>
> > +#include <stdint.h>
> > +
> > +extern int get_buf_size ();
> > +
> > +void var_too_short ()
> > +{
> > + int8_t s;
> > + int64_t *lp = new (&s) int64_t; /* { dg-warning "stack-based
> > buffer overflow" } */
> > + /* { dg-warning "allocated buffer size is not a multiple of the
> > pointee's size" "" { target *-*-* } .-1 } */
> > +}
> > +
> > +void static_buffer_too_short ()
> > +{
> > + int n = 16;
> > + int buf[n];
> > + int *p = new (buf) int[n + 1]; /* { dg-warning "stack-based buffer
> > overflow" } */
> > +}
> > +
> > +void symbolic_buffer_too_short ()
> > +{
> > + int n = get_buf_size ();
> > + char buf[n];
> > + char *p = new (buf) char[n + 10]; /* { dg-warning "stack-based
> > buffer overflow" } */
> > +}
> > diff --git a/gcc/testsuite/g++.dg/analyzer/placement-new.C
> > b/gcc/testsuite/g++.dg/analyzer/placement-new.C
> > index 89055491a48..8edd778131b 100644
> > --- a/gcc/testsuite/g++.dg/analyzer/placement-new.C
> > +++ b/gcc/testsuite/g++.dg/analyzer/placement-new.C
> > @@ -1,3 +1,5 @@
> > +/* { dg-additional-options "-Wno-free-nonheap-object -fexceptions" }
> > */
> > +
> > #include <new>
> >
> > /* Placement new. */
> > @@ -14,15 +16,101 @@ void test_2 (void)
> > {
> > char buf[sizeof(int) * 10];
> > int *p = new(buf) int[10];
> > -}
> > +} // { dg-prune-output "-Wfree-nonheap-object" }
> >
> > /* Delete of placement new. */
> >
> > void test_3 (void)
> > {
> > char buf[sizeof(int)]; // { dg-message "region created on stack
> > here" }
> > - int *p = new(buf) int (42);
> > + int *p = new (buf) int (42);
> > + delete p; // { dg-warning "memory on the stack" }
> > +}
> > +
> > +// { dg-prune-output "-Wfree-nonheap-object" }
> > +
> > +void test_4 (void)
> > +{
> > + int buf[5]; // { dg-message "region created on stack here" }
> > + int *p = new (&buf[2]) int (42);
> > delete p; // { dg-warning "memory on the stack" }
> > }
> >
> > +
> > // { dg-prune-output "-Wfree-nonheap-object" }
> > +
> > +void test_write_placement_after_delete (void)
> > +{
> > + short *s = ::new short;
> > + short *lp = ::new (s) short;
> > + ::delete s;
> > + *lp = 12; /* { dg-warning "use after 'delete' of 'lp'" "write
> > placement new after buffer deletion" } */
> > +}
> > +
> > +void test_read_placement_after_delete (void)
> > +{
> > + short *s = ::new short;
> > + short *lp = ::new (s) short;
> > + ::delete s;
> > + short m = *lp; // { dg-warning "use after 'delete' of 'lp'" "read
> > placement new after buffer deletion" }
> > +}
> > +
> > +struct A
> > +{
> > + int x;
> > + int y;
> > +};
> > +
> > +void test_use_placement_after_destruction (void)
> > +{
> > + A a;
> > + int *lp = ::new (&a.y) int;
> > + *lp = 2; /* { dg-bogus "-Wanalyzer-use-of-uninitialized-value" }
> > */
> > + a.~A();
> > + int m = *lp; /* { dg-warning "use of uninitialized value '\\*lp'"
> > "use of placement after the underlying buffer was destructed." } */
> > +}
> > +
> > +void test_initialization_through_placement (void)
> > +{
> > + int x;
> > + int *p = ::new (&x) int;
> > + *p = 10;
> > + int z = x + 2; /* { dg-bogus "use of uninitialized value 'x'" "x
> > has been initialized through placement pointer" } */
> > +}
> > +
> > +void test_partial_initialization_through_placement (void)
> > +{
> > + char buf[4];
> > + char *p = ::new (&buf[2]) char;
> > + *p = 10;
> > + char *y = ::new (&buf[0]) char;
> > + char z = buf[2] + 2; /* { dg-bogus "use of uninitialized value" }
> > */
> > + z = *y + 2; /* { dg-warning "use of uninitialized value '\\*y'" "y
> > has only been partially initialized" } */
> > +}
> > +
> > +
> > +void test_delete_placement (void)
> > +{
> > + A *a = ::new A; /* { dg-bogus "use of possibly-NULL 'operator
> > new(8)' where non-null expected" "throwing new cannot be null" } */
> > + int *z = ::new (&a->y) int;
> > + a->~A(); // deconstruct properly
> > + ::operator delete (a);
> > + ::operator delete (z); /* { dg-warning "use after 'delete' of 'z'"
> > } */
> > +}
> > +
> > +void test_delete_placement_2 (void)
> > +{
> > + A *a = ::new A; /* { dg-bogus "use of possibly-NULL 'operator
> > new(8)' where non-null expected" "throwing new cannot be null" } */
> > + int *z = ::new (&a->y) int;
> > + delete a;
> > + ::operator delete (z); /* { dg-warning "use after 'delete' of 'z'"
> > } */
> > +}
> > +
> > +void test_use_placement_after_deallocation (void)
> > +{
> > + A *a = ::new A ();
> > + int *lp = ::new (&a->y) int;
> > + *lp = 2; /* { dg-bogus "use of uninitialized value" } */
> > + ::operator delete (a);
> > + int m = *lp; /* { dg-warning "use after 'delete' of 'lp'" "use of
> > placement after the underlying buffer was deallocated." } */
> > +}
>
>
