diff mbox series

c++: non-dependent .* folding [PR112427]

Message ID 20231108215904.2779753-1-ppalka@redhat.com
State New
Headers show
Series c++: non-dependent .* folding [PR112427] | expand

Commit Message

Patrick Palka Nov. 8, 2023, 9:59 p.m. UTC 
Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
trunk?

-- >8 --

Here when building up the non-dependent .* expression, we crash from
fold_convert on 'b.a' due to this (templated) COMPONENT_REF having an
IDENTIFIER_NODE instead of FIELD_DECL operand that middle-end routines
expect.  Like in r14-4899-gd80a26cca02587, this patch fixes this by
replacing the problematic piecemeal folding with a single call to
cp_fully_fold.

	PR c++/112427

gcc/cp/ChangeLog:

	* typeck2.cc (build_m_component_ref): Use cp_convert, build2 and
	cp_fully_fold instead of fold_build_pointer_plus and fold_convert.

gcc/testsuite/ChangeLog:

	* g++.dg/template/non-dependent29.C: New test.
---
 gcc/cp/typeck2.cc                               |  5 ++++-
 gcc/testsuite/g++.dg/template/non-dependent29.C | 13 +++++++++++++
 2 files changed, 17 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/g++.dg/template/non-dependent29.C

Comments

Jason Merrill Nov. 10, 2023, 12:28 a.m. UTC | #1 
On 11/8/23 16:59, Patrick Palka wrote:
> Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
> trunk?
> 
> -- >8 --
> 
> Here when building up the non-dependent .* expression, we crash from
> fold_convert on 'b.a' due to this (templated) COMPONENT_REF having an
> IDENTIFIER_NODE instead of FIELD_DECL operand that middle-end routines
> expect.  Like in r14-4899-gd80a26cca02587, this patch fixes this by
> replacing the problematic piecemeal folding with a single call to
> cp_fully_fold.
> 
> 	PR c++/112427
> 
> gcc/cp/ChangeLog:
> 
> 	* typeck2.cc (build_m_component_ref): Use cp_convert, build2 and
> 	cp_fully_fold instead of fold_build_pointer_plus and fold_convert.

> gcc/testsuite/ChangeLog:
> 
> 	* g++.dg/template/non-dependent29.C: New test.
> ---
>   gcc/cp/typeck2.cc                               |  5 ++++-
>   gcc/testsuite/g++.dg/template/non-dependent29.C | 13 +++++++++++++
>   2 files changed, 17 insertions(+), 1 deletion(-)
>   create mode 100644 gcc/testsuite/g++.dg/template/non-dependent29.C
> 
> diff --git a/gcc/cp/typeck2.cc b/gcc/cp/typeck2.cc
> index 309903afed8..208004221da 100644
> --- a/gcc/cp/typeck2.cc
> +++ b/gcc/cp/typeck2.cc
> @@ -2378,7 +2378,10 @@ build_m_component_ref (tree datum, tree component, tsubst_flags_t complain)
>         /* Build an expression for "object + offset" where offset is the
>   	 value stored in the pointer-to-data-member.  */
>         ptype = build_pointer_type (type);
> -      datum = fold_build_pointer_plus (fold_convert (ptype, datum), component);
> +      datum = cp_convert (ptype, datum, complain);
> +      datum = build2 (POINTER_PLUS_EXPR, ptype,
> +		      datum, convert_to_ptrofftype (component));

We shouldn't need to build the POINTER_PLUS_EXPR at all in template 
context.  OK with that change.

Jason
Patrick Palka Nov. 10, 2023, 3:12 p.m. UTC | #2 
On Thu, 9 Nov 2023, Jason Merrill wrote:

> On 11/8/23 16:59, Patrick Palka wrote:
> > Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
> > trunk?
> > 
> > -- >8 --
> > 
> > Here when building up the non-dependent .* expression, we crash from
> > fold_convert on 'b.a' due to this (templated) COMPONENT_REF having an
> > IDENTIFIER_NODE instead of FIELD_DECL operand that middle-end routines
> > expect.  Like in r14-4899-gd80a26cca02587, this patch fixes this by
> > replacing the problematic piecemeal folding with a single call to
> > cp_fully_fold.
> > 
> > 	PR c++/112427
> > 
> > gcc/cp/ChangeLog:
> > 
> > 	* typeck2.cc (build_m_component_ref): Use cp_convert, build2 and
> > 	cp_fully_fold instead of fold_build_pointer_plus and fold_convert.
> 
> > gcc/testsuite/ChangeLog:
> > 
> > 	* g++.dg/template/non-dependent29.C: New test.
> > ---
> >   gcc/cp/typeck2.cc                               |  5 ++++-
> >   gcc/testsuite/g++.dg/template/non-dependent29.C | 13 +++++++++++++
> >   2 files changed, 17 insertions(+), 1 deletion(-)
> >   create mode 100644 gcc/testsuite/g++.dg/template/non-dependent29.C
> > 
> > diff --git a/gcc/cp/typeck2.cc b/gcc/cp/typeck2.cc
> > index 309903afed8..208004221da 100644
> > --- a/gcc/cp/typeck2.cc
> > +++ b/gcc/cp/typeck2.cc
> > @@ -2378,7 +2378,10 @@ build_m_component_ref (tree datum, tree component,
> > tsubst_flags_t complain)
> >         /* Build an expression for "object + offset" where offset is the
> >   	 value stored in the pointer-to-data-member.  */
> >         ptype = build_pointer_type (type);
> > -      datum = fold_build_pointer_plus (fold_convert (ptype, datum),
> > component);
> > +      datum = cp_convert (ptype, datum, complain);
> > +      datum = build2 (POINTER_PLUS_EXPR, ptype,
> > +		      datum, convert_to_ptrofftype (component));
> 
> We shouldn't need to build the POINTER_PLUS_EXPR at all in template context.
> OK with that change.

Hmm, that seems harmless at first glance, but I noticed
build_min_non_dep (called from build_x_binary_op in this case) is
careful to propagate TREE_SIDE_EFFECTS of the given tree, and so eliding
POINTER_PLUS_EXPR here could potentially mean that the tree we
ultimately return from build_x_binary_op when in a template context has
TREE_SIDE_EFFECTS not set when it used to.  Shall we still elide the
POINTER_PLUS_EXPR in a template context despite this?

(The TREE_SIDE_EFFECTS propagation in build_min_non_dep was added in
r71108 to avoid bogus ahead of time -Wunused-value warnings.  But then
r105273 later made us stop issuing -Wunused-value warnings ahead of time
altogether.  So perhaps we don't need to maintain the TREE_SIDE_EFFECTS
flag on templated trees at all anymore?)

> 
> Jason
> 
>
Patrick Palka Nov. 10, 2023, 3:28 p.m. UTC | #3 
On Fri, 10 Nov 2023, Patrick Palka wrote:

> On Thu, 9 Nov 2023, Jason Merrill wrote:
> 
> > On 11/8/23 16:59, Patrick Palka wrote:
> > > Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
> > > trunk?
> > > 
> > > -- >8 --
> > > 
> > > Here when building up the non-dependent .* expression, we crash from
> > > fold_convert on 'b.a' due to this (templated) COMPONENT_REF having an
> > > IDENTIFIER_NODE instead of FIELD_DECL operand that middle-end routines
> > > expect.  Like in r14-4899-gd80a26cca02587, this patch fixes this by
> > > replacing the problematic piecemeal folding with a single call to
> > > cp_fully_fold.
> > > 
> > > 	PR c++/112427
> > > 
> > > gcc/cp/ChangeLog:
> > > 
> > > 	* typeck2.cc (build_m_component_ref): Use cp_convert, build2 and
> > > 	cp_fully_fold instead of fold_build_pointer_plus and fold_convert.
> > 
> > > gcc/testsuite/ChangeLog:
> > > 
> > > 	* g++.dg/template/non-dependent29.C: New test.
> > > ---
> > >   gcc/cp/typeck2.cc                               |  5 ++++-
> > >   gcc/testsuite/g++.dg/template/non-dependent29.C | 13 +++++++++++++
> > >   2 files changed, 17 insertions(+), 1 deletion(-)
> > >   create mode 100644 gcc/testsuite/g++.dg/template/non-dependent29.C
> > > 
> > > diff --git a/gcc/cp/typeck2.cc b/gcc/cp/typeck2.cc
> > > index 309903afed8..208004221da 100644
> > > --- a/gcc/cp/typeck2.cc
> > > +++ b/gcc/cp/typeck2.cc
> > > @@ -2378,7 +2378,10 @@ build_m_component_ref (tree datum, tree component,
> > > tsubst_flags_t complain)
> > >         /* Build an expression for "object + offset" where offset is the
> > >   	 value stored in the pointer-to-data-member.  */
> > >         ptype = build_pointer_type (type);
> > > -      datum = fold_build_pointer_plus (fold_convert (ptype, datum),
> > > component);
> > > +      datum = cp_convert (ptype, datum, complain);
> > > +      datum = build2 (POINTER_PLUS_EXPR, ptype,
> > > +		      datum, convert_to_ptrofftype (component));
> > 
> > We shouldn't need to build the POINTER_PLUS_EXPR at all in template context.
> > OK with that change.
> 
> Hmm, that seems harmless at first glance, but I noticed
> build_min_non_dep (called from build_x_binary_op in this case) is
> careful to propagate TREE_SIDE_EFFECTS of the given tree, and so eliding
> POINTER_PLUS_EXPR here could potentially mean that the tree we
> ultimately return from build_x_binary_op when in a template context has
> TREE_SIDE_EFFECTS not set when it used to.  Shall we still elide the
> POINTER_PLUS_EXPR in a template context despite this?
> 
> (The TREE_SIDE_EFFECTS propagation in build_min_non_dep was added in
> r71108 to avoid bogus ahead of time -Wunused-value warnings.  But then
> r105273 later made us stop issuing -Wunused-value warnings ahead of time
> altogether.  So perhaps we don't need to maintain the TREE_SIDE_EFFECTS
> flag on templated trees at all anymore?)

IMO it'd be nice to restore ahead of time -Wunused-value warnings;
it seems the original motivation for r105273 / PR8057 was to avoid
redundantly issuing a warning twice, once ahead of time and once at
instantiation time, which we now could do in a better way with
warning_suppressed_p etc.  If so, then IIUC eliding the POINTER_PLUS_EXPR
could mean we'd incorrectly issue a -Wunused-value warning for e.g.
'a.*f()' in a template context?

> 
> > 
> > Jason
> > 
> > 
>
Jason Merrill Nov. 10, 2023, 9:36 p.m. UTC | #4 
On 11/10/23 10:28, Patrick Palka wrote:
> On Fri, 10 Nov 2023, Patrick Palka wrote:
> 
>> On Thu, 9 Nov 2023, Jason Merrill wrote:
>>
>>> On 11/8/23 16:59, Patrick Palka wrote:
>>>> Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
>>>> trunk?
>>>>
>>>> -- >8 --
>>>>
>>>> Here when building up the non-dependent .* expression, we crash from
>>>> fold_convert on 'b.a' due to this (templated) COMPONENT_REF having an
>>>> IDENTIFIER_NODE instead of FIELD_DECL operand that middle-end routines
>>>> expect.  Like in r14-4899-gd80a26cca02587, this patch fixes this by
>>>> replacing the problematic piecemeal folding with a single call to
>>>> cp_fully_fold.
>>>>
>>>> 	PR c++/112427
>>>>
>>>> gcc/cp/ChangeLog:
>>>>
>>>> 	* typeck2.cc (build_m_component_ref): Use cp_convert, build2 and
>>>> 	cp_fully_fold instead of fold_build_pointer_plus and fold_convert.
>>>
>>>> gcc/testsuite/ChangeLog:
>>>>
>>>> 	* g++.dg/template/non-dependent29.C: New test.
>>>> ---
>>>>    gcc/cp/typeck2.cc                               |  5 ++++-
>>>>    gcc/testsuite/g++.dg/template/non-dependent29.C | 13 +++++++++++++
>>>>    2 files changed, 17 insertions(+), 1 deletion(-)
>>>>    create mode 100644 gcc/testsuite/g++.dg/template/non-dependent29.C
>>>>
>>>> diff --git a/gcc/cp/typeck2.cc b/gcc/cp/typeck2.cc
>>>> index 309903afed8..208004221da 100644
>>>> --- a/gcc/cp/typeck2.cc
>>>> +++ b/gcc/cp/typeck2.cc
>>>> @@ -2378,7 +2378,10 @@ build_m_component_ref (tree datum, tree component,
>>>> tsubst_flags_t complain)
>>>>          /* Build an expression for "object + offset" where offset is the
>>>>    	 value stored in the pointer-to-data-member.  */
>>>>          ptype = build_pointer_type (type);
>>>> -      datum = fold_build_pointer_plus (fold_convert (ptype, datum),
>>>> component);
>>>> +      datum = cp_convert (ptype, datum, complain);
>>>> +      datum = build2 (POINTER_PLUS_EXPR, ptype,
>>>> +		      datum, convert_to_ptrofftype (component));
>>>
>>> We shouldn't need to build the POINTER_PLUS_EXPR at all in template context.
>>> OK with that change.
>>
>> Hmm, that seems harmless at first glance, but I noticed
>> build_min_non_dep (called from build_x_binary_op in this case) is
>> careful to propagate TREE_SIDE_EFFECTS of the given tree, and so eliding
>> POINTER_PLUS_EXPR here could potentially mean that the tree we
>> ultimately return from build_x_binary_op when in a template context has
>> TREE_SIDE_EFFECTS not set when it used to.  Shall we still elide the
>> POINTER_PLUS_EXPR in a template context despite this?

True, we would need build_min_non_dep to also get TREE_SIDE_EFFECTS from 
the operands.  That might be useful in general for similar situations?

I also note that convert_to_ptrofftype uses fold_convert, so the new 
code could have the same problem if the pointer to member operand is 
also a COMPONENT_REF.

Jason
Patrick Palka Nov. 14, 2023, 3:43 p.m. UTC | #5 
On Fri, 10 Nov 2023, Jason Merrill wrote:

> On 11/10/23 10:28, Patrick Palka wrote:
> > On Fri, 10 Nov 2023, Patrick Palka wrote:
> > 
> > > On Thu, 9 Nov 2023, Jason Merrill wrote:
> > > 
> > > > On 11/8/23 16:59, Patrick Palka wrote:
> > > > > Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK
> > > > > for
> > > > > trunk?
> > > > > 
> > > > > -- >8 --
> > > > > 
> > > > > Here when building up the non-dependent .* expression, we crash from
> > > > > fold_convert on 'b.a' due to this (templated) COMPONENT_REF having an
> > > > > IDENTIFIER_NODE instead of FIELD_DECL operand that middle-end routines
> > > > > expect.  Like in r14-4899-gd80a26cca02587, this patch fixes this by
> > > > > replacing the problematic piecemeal folding with a single call to
> > > > > cp_fully_fold.
> > > > > 
> > > > > 	PR c++/112427
> > > > > 
> > > > > gcc/cp/ChangeLog:
> > > > > 
> > > > > 	* typeck2.cc (build_m_component_ref): Use cp_convert, build2
> > > > > and
> > > > > 	cp_fully_fold instead of fold_build_pointer_plus and
> > > > > fold_convert.
> > > > 
> > > > > gcc/testsuite/ChangeLog:
> > > > > 
> > > > > 	* g++.dg/template/non-dependent29.C: New test.
> > > > > ---
> > > > >    gcc/cp/typeck2.cc                               |  5 ++++-
> > > > >    gcc/testsuite/g++.dg/template/non-dependent29.C | 13 +++++++++++++
> > > > >    2 files changed, 17 insertions(+), 1 deletion(-)
> > > > >    create mode 100644 gcc/testsuite/g++.dg/template/non-dependent29.C
> > > > > 
> > > > > diff --git a/gcc/cp/typeck2.cc b/gcc/cp/typeck2.cc
> > > > > index 309903afed8..208004221da 100644
> > > > > --- a/gcc/cp/typeck2.cc
> > > > > +++ b/gcc/cp/typeck2.cc
> > > > > @@ -2378,7 +2378,10 @@ build_m_component_ref (tree datum, tree
> > > > > component,
> > > > > tsubst_flags_t complain)
> > > > >          /* Build an expression for "object + offset" where offset is
> > > > > the
> > > > >    	 value stored in the pointer-to-data-member.  */
> > > > >          ptype = build_pointer_type (type);
> > > > > -      datum = fold_build_pointer_plus (fold_convert (ptype, datum),
> > > > > component);
> > > > > +      datum = cp_convert (ptype, datum, complain);
> > > > > +      datum = build2 (POINTER_PLUS_EXPR, ptype,
> > > > > +		      datum, convert_to_ptrofftype (component));
> > > > 
> > > > We shouldn't need to build the POINTER_PLUS_EXPR at all in template
> > > > context.
> > > > OK with that change.
> > > 
> > > Hmm, that seems harmless at first glance, but I noticed
> > > build_min_non_dep (called from build_x_binary_op in this case) is
> > > careful to propagate TREE_SIDE_EFFECTS of the given tree, and so eliding
> > > POINTER_PLUS_EXPR here could potentially mean that the tree we
> > > ultimately return from build_x_binary_op when in a template context has
> > > TREE_SIDE_EFFECTS not set when it used to.  Shall we still elide the
> > > POINTER_PLUS_EXPR in a template context despite this?
> 
> True, we would need build_min_non_dep to also get TREE_SIDE_EFFECTS from the
> operands.  That might be useful in general for similar situations?
> 
> I also note that convert_to_ptrofftype uses fold_convert, so the new code
> could have the same problem if the pointer to member operand is also a
> COMPONENT_REF.

Ah, makes sense...  How does the following look then?  I'm not sure if
we still want to replace fold_build_pointer_plus with build2 if we're
not going to use that code path in a template context?  Bootstrapped and
regtested on x86_64-pc-linux-gnu.

-- >8 --
-
Subject: [PATCH] c++: non-dependent .* operand folding [PR112427]

Here when building up the non-dependent .* expression, we crash from
fold_convert on 'b.a' due to this (templated) COMPONENT_REF having an
IDENTIFIER_NODE instead of FIELD_DECL operand that middle-end routines
expect.  Like in r14-4899-gd80a26cca02587, this patch fixes this by
replacing the problematic piecemeal folding with a single call to
cp_fully_fold.  Additionally, don't bother building POINTER_PLUS_EXPR
in a template context.  This means the returned non-dependent tree might
not have TREE_SIDE_EFFECTS set when it used to, so we need to make
build_min_non_dep compensate for this by propagating TREE_SIDE_EFFECTS
from the original arguments like buildN and build_min do, which seems
like a generally desirable thing to do anyway.

	PR c++/112427

gcc/cp/ChangeLog:

	* tree.cc (build_min_non_dep): Propagate TREE_SIDE_EFFECTS from
	the original arguments.
	(build_min_non_dep_call_vec): Likewise.
	* typeck2.cc (build_m_component_ref): Use cp_convert, build2 and
	cp_fully_fold instead of fold_build_pointer_plus and fold_convert.

gcc/testsuite/ChangeLog:

	* g++.dg/template/non-dependent29.C: New test.
---
 gcc/cp/tree.cc                                  | 11 ++++++++++-
 gcc/cp/typeck2.cc                               |  6 +++++-
 gcc/testsuite/g++.dg/template/non-dependent29.C | 13 +++++++++++++
 3 files changed, 28 insertions(+), 2 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/template/non-dependent29.C

diff --git a/gcc/cp/tree.cc b/gcc/cp/tree.cc
index 417c92ba76f..dc4126f935c 100644
--- a/gcc/cp/tree.cc
+++ b/gcc/cp/tree.cc
@@ -3601,7 +3601,12 @@ build_min_non_dep (enum tree_code code, tree non_dep, ...)
   TREE_SIDE_EFFECTS (t) = TREE_SIDE_EFFECTS (non_dep);
 
   for (i = 0; i < length; i++)
-    TREE_OPERAND (t, i) = va_arg (p, tree);
+    {
+      tree x = va_arg (p, tree);
+      TREE_OPERAND (t, i) = x;
+      if (x && !TYPE_P (x))
+	TREE_SIDE_EFFECTS (t) |= TREE_SIDE_EFFECTS (x);
+    }
 
   va_end (p);
   return convert_from_reference (t);
@@ -3636,6 +3641,10 @@ build_min_non_dep_call_vec (tree non_dep, tree fn, vec<tree, va_gc> *argvec)
     non_dep = TREE_OPERAND (non_dep, 0);
   TREE_TYPE (t) = TREE_TYPE (non_dep);
   TREE_SIDE_EFFECTS (t) = TREE_SIDE_EFFECTS (non_dep);
+  if (argvec)
+    for (tree x : *argvec)
+      if (x && !TYPE_P (x))
+	TREE_SIDE_EFFECTS (t) |= TREE_SIDE_EFFECTS (x);
   return convert_from_reference (t);
 }
 
diff --git a/gcc/cp/typeck2.cc b/gcc/cp/typeck2.cc
index 309903afed8..a75f4f8c2d2 100644
--- a/gcc/cp/typeck2.cc
+++ b/gcc/cp/typeck2.cc
@@ -2378,7 +2378,11 @@ build_m_component_ref (tree datum, tree component, tsubst_flags_t complain)
       /* Build an expression for "object + offset" where offset is the
 	 value stored in the pointer-to-data-member.  */
       ptype = build_pointer_type (type);
-      datum = fold_build_pointer_plus (fold_convert (ptype, datum), component);
+      datum = cp_convert (ptype, datum, complain);
+      if (!processing_template_decl)
+	datum = build2 (POINTER_PLUS_EXPR, ptype,
+			datum, convert_to_ptrofftype (component));
+      datum = cp_fully_fold (datum);
       datum = cp_build_fold_indirect_ref (datum);
       if (datum == error_mark_node)
 	return error_mark_node;
diff --git a/gcc/testsuite/g++.dg/template/non-dependent29.C b/gcc/testsuite/g++.dg/template/non-dependent29.C
new file mode 100644
index 00000000000..41bd11ae6b4
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/non-dependent29.C
@@ -0,0 +1,13 @@
+// PR c++/112427
+
+struct A { int m; void f(); };
+struct B { A a; };
+
+template<class T>
+void f(B b) {
+  int A::*pd = &A::m;
+  b.a.*pd;
+
+  void (A::*pf)() = &A::f;
+  (b.a.*pf)();
+}
Jason Merrill Nov. 14, 2023, 10:29 p.m. UTC | #6 
On 11/14/23 10:43, Patrick Palka wrote:
> On Fri, 10 Nov 2023, Jason Merrill wrote:
> 
>> On 11/10/23 10:28, Patrick Palka wrote:
>>> On Fri, 10 Nov 2023, Patrick Palka wrote:
>>>
>>>> On Thu, 9 Nov 2023, Jason Merrill wrote:
>>>>
>>>>> On 11/8/23 16:59, Patrick Palka wrote:
>>>>>> Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK
>>>>>> for
>>>>>> trunk?
>>>>>>
>>>>>> -- >8 --
>>>>>>
>>>>>> Here when building up the non-dependent .* expression, we crash from
>>>>>> fold_convert on 'b.a' due to this (templated) COMPONENT_REF having an
>>>>>> IDENTIFIER_NODE instead of FIELD_DECL operand that middle-end routines
>>>>>> expect.  Like in r14-4899-gd80a26cca02587, this patch fixes this by
>>>>>> replacing the problematic piecemeal folding with a single call to
>>>>>> cp_fully_fold.
>>>>>>
>>>>>> 	PR c++/112427
>>>>>>
>>>>>> gcc/cp/ChangeLog:
>>>>>>
>>>>>> 	* typeck2.cc (build_m_component_ref): Use cp_convert, build2
>>>>>> and
>>>>>> 	cp_fully_fold instead of fold_build_pointer_plus and
>>>>>> fold_convert.
>>>>>
>>>>>> gcc/testsuite/ChangeLog:
>>>>>>
>>>>>> 	* g++.dg/template/non-dependent29.C: New test.
>>>>>> ---
>>>>>>     gcc/cp/typeck2.cc                               |  5 ++++-
>>>>>>     gcc/testsuite/g++.dg/template/non-dependent29.C | 13 +++++++++++++
>>>>>>     2 files changed, 17 insertions(+), 1 deletion(-)
>>>>>>     create mode 100644 gcc/testsuite/g++.dg/template/non-dependent29.C
>>>>>>
>>>>>> diff --git a/gcc/cp/typeck2.cc b/gcc/cp/typeck2.cc
>>>>>> index 309903afed8..208004221da 100644
>>>>>> --- a/gcc/cp/typeck2.cc
>>>>>> +++ b/gcc/cp/typeck2.cc
>>>>>> @@ -2378,7 +2378,10 @@ build_m_component_ref (tree datum, tree
>>>>>> component,
>>>>>> tsubst_flags_t complain)
>>>>>>           /* Build an expression for "object + offset" where offset is
>>>>>> the
>>>>>>     	 value stored in the pointer-to-data-member.  */
>>>>>>           ptype = build_pointer_type (type);
>>>>>> -      datum = fold_build_pointer_plus (fold_convert (ptype, datum),
>>>>>> component);
>>>>>> +      datum = cp_convert (ptype, datum, complain);
>>>>>> +      datum = build2 (POINTER_PLUS_EXPR, ptype,
>>>>>> +		      datum, convert_to_ptrofftype (component));
>>>>>
>>>>> We shouldn't need to build the POINTER_PLUS_EXPR at all in template
>>>>> context.
>>>>> OK with that change.
>>>>
>>>> Hmm, that seems harmless at first glance, but I noticed
>>>> build_min_non_dep (called from build_x_binary_op in this case) is
>>>> careful to propagate TREE_SIDE_EFFECTS of the given tree, and so eliding
>>>> POINTER_PLUS_EXPR here could potentially mean that the tree we
>>>> ultimately return from build_x_binary_op when in a template context has
>>>> TREE_SIDE_EFFECTS not set when it used to.  Shall we still elide the
>>>> POINTER_PLUS_EXPR in a template context despite this?
>>
>> True, we would need build_min_non_dep to also get TREE_SIDE_EFFECTS from the
>> operands.  That might be useful in general for similar situations?
>>
>> I also note that convert_to_ptrofftype uses fold_convert, so the new code
>> could have the same problem if the pointer to member operand is also a
>> COMPONENT_REF.
> 
> Ah, makes sense...  How does the following look then?  I'm not sure if
> we still want to replace fold_build_pointer_plus with build2 if we're
> not going to use that code path in a template context?  Bootstrapped and
> regtested on x86_64-pc-linux-gnu.

We probably do, since we now aren't folding the thing before it.  OK.

> -- >8 --
> -
> Subject: [PATCH] c++: non-dependent .* operand folding [PR112427]
> 
> Here when building up the non-dependent .* expression, we crash from
> fold_convert on 'b.a' due to this (templated) COMPONENT_REF having an
> IDENTIFIER_NODE instead of FIELD_DECL operand that middle-end routines
> expect.  Like in r14-4899-gd80a26cca02587, this patch fixes this by
> replacing the problematic piecemeal folding with a single call to
> cp_fully_fold.  Additionally, don't bother building POINTER_PLUS_EXPR
> in a template context.  This means the returned non-dependent tree might
> not have TREE_SIDE_EFFECTS set when it used to, so we need to make
> build_min_non_dep compensate for this by propagating TREE_SIDE_EFFECTS
> from the original arguments like buildN and build_min do, which seems
> like a generally desirable thing to do anyway.
> 
> 	PR c++/112427
> 
> gcc/cp/ChangeLog:
> 
> 	* tree.cc (build_min_non_dep): Propagate TREE_SIDE_EFFECTS from
> 	the original arguments.
> 	(build_min_non_dep_call_vec): Likewise.
> 	* typeck2.cc (build_m_component_ref): Use cp_convert, build2 and
> 	cp_fully_fold instead of fold_build_pointer_plus and fold_convert.
> 
> gcc/testsuite/ChangeLog:
> 
> 	* g++.dg/template/non-dependent29.C: New test.
> ---
>   gcc/cp/tree.cc                                  | 11 ++++++++++-
>   gcc/cp/typeck2.cc                               |  6 +++++-
>   gcc/testsuite/g++.dg/template/non-dependent29.C | 13 +++++++++++++
>   3 files changed, 28 insertions(+), 2 deletions(-)
>   create mode 100644 gcc/testsuite/g++.dg/template/non-dependent29.C
> 
> diff --git a/gcc/cp/tree.cc b/gcc/cp/tree.cc
> index 417c92ba76f..dc4126f935c 100644
> --- a/gcc/cp/tree.cc
> +++ b/gcc/cp/tree.cc
> @@ -3601,7 +3601,12 @@ build_min_non_dep (enum tree_code code, tree non_dep, ...)
>     TREE_SIDE_EFFECTS (t) = TREE_SIDE_EFFECTS (non_dep);
>   
>     for (i = 0; i < length; i++)
> -    TREE_OPERAND (t, i) = va_arg (p, tree);
> +    {
> +      tree x = va_arg (p, tree);
> +      TREE_OPERAND (t, i) = x;
> +      if (x && !TYPE_P (x))
> +	TREE_SIDE_EFFECTS (t) |= TREE_SIDE_EFFECTS (x);
> +    }
>   
>     va_end (p);
>     return convert_from_reference (t);
> @@ -3636,6 +3641,10 @@ build_min_non_dep_call_vec (tree non_dep, tree fn, vec<tree, va_gc> *argvec)
>       non_dep = TREE_OPERAND (non_dep, 0);
>     TREE_TYPE (t) = TREE_TYPE (non_dep);
>     TREE_SIDE_EFFECTS (t) = TREE_SIDE_EFFECTS (non_dep);
> +  if (argvec)
> +    for (tree x : *argvec)
> +      if (x && !TYPE_P (x))
> +	TREE_SIDE_EFFECTS (t) |= TREE_SIDE_EFFECTS (x);
>     return convert_from_reference (t);
>   }
>   
> diff --git a/gcc/cp/typeck2.cc b/gcc/cp/typeck2.cc
> index 309903afed8..a75f4f8c2d2 100644
> --- a/gcc/cp/typeck2.cc
> +++ b/gcc/cp/typeck2.cc
> @@ -2378,7 +2378,11 @@ build_m_component_ref (tree datum, tree component, tsubst_flags_t complain)
>         /* Build an expression for "object + offset" where offset is the
>   	 value stored in the pointer-to-data-member.  */
>         ptype = build_pointer_type (type);
> -      datum = fold_build_pointer_plus (fold_convert (ptype, datum), component);
> +      datum = cp_convert (ptype, datum, complain);
> +      if (!processing_template_decl)
> +	datum = build2 (POINTER_PLUS_EXPR, ptype,
> +			datum, convert_to_ptrofftype (component));
> +      datum = cp_fully_fold (datum);
>         datum = cp_build_fold_indirect_ref (datum);
>         if (datum == error_mark_node)
>   	return error_mark_node;
> diff --git a/gcc/testsuite/g++.dg/template/non-dependent29.C b/gcc/testsuite/g++.dg/template/non-dependent29.C
> new file mode 100644
> index 00000000000..41bd11ae6b4
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/template/non-dependent29.C
> @@ -0,0 +1,13 @@
> +// PR c++/112427
> +
> +struct A { int m; void f(); };
> +struct B { A a; };
> +
> +template<class T>
> +void f(B b) {
> +  int A::*pd = &A::m;
> +  b.a.*pd;
> +
> +  void (A::*pf)() = &A::f;
> +  (b.a.*pf)();
> +}
diff mbox series

Patch

diff --git a/gcc/cp/typeck2.cc b/gcc/cp/typeck2.cc
index 309903afed8..208004221da 100644
--- a/gcc/cp/typeck2.cc
+++ b/gcc/cp/typeck2.cc
@@ -2378,7 +2378,10 @@  build_m_component_ref (tree datum, tree component, tsubst_flags_t complain)
       /* Build an expression for "object + offset" where offset is the
 	 value stored in the pointer-to-data-member.  */
       ptype = build_pointer_type (type);
-      datum = fold_build_pointer_plus (fold_convert (ptype, datum), component);
+      datum = cp_convert (ptype, datum, complain);
+      datum = build2 (POINTER_PLUS_EXPR, ptype,
+		      datum, convert_to_ptrofftype (component));
+      datum = cp_fully_fold (datum);
       datum = cp_build_fold_indirect_ref (datum);
       if (datum == error_mark_node)
 	return error_mark_node;
diff --git a/gcc/testsuite/g++.dg/template/non-dependent29.C b/gcc/testsuite/g++.dg/template/non-dependent29.C
new file mode 100644
index 00000000000..41bd11ae6b4
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/non-dependent29.C
@@ -0,0 +1,13 @@ 
+// PR c++/112427
+
+struct A { int m; void f(); };
+struct B { A a; };
+
+template<class T>
+void f(B b) {
+  int A::*pd = &A::m;
+  b.a.*pd;
+
+  void (A::*pf)() = &A::f;
+  (b.a.*pf)();
+}