On Wed, 2023-08-16 at 14:19 +0200, [email protected] wrote:
> From: benjamin priour <[email protected]>
>
> 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.
> 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?
>
> <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.
> 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.
> 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).
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 <[email protected]>
>
> 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." } */
> +}
