[v3] c++: fix ICE with sizeof in a template [PR112869]
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On Fri, Dec 08, 2023 at 11:09:15PM -0500, Jason Merrill wrote:
> On 12/8/23 16:15, Marek Polacek wrote:
> > On Fri, Dec 08, 2023 at 12:09:18PM -0500, Jason Merrill wrote:
> > > On 12/5/23 15:31, Marek Polacek wrote:
> > > > Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
> > > >
> > > > -- >8 --
> > > > This test shows that we cannot clear *walk_subtrees in
> > > > cp_fold_immediate_r when we're in_immediate_context, because that,
> > > > as the comment says, affects cp_fold_r as well. Here we had an
> > > > expression with
> > > >
> > > > min ((long int) VIEW_CONVERT_EXPR<long unsigned int>(bytecount), (long int) <<< Unknown tree: sizeof_expr
> > > > (int) <<< error >>> >>>)
> > > >
> > > > as its sub-expression, and we never evaluated that into
> > > >
> > > > min ((long int) bytecount, 4)
> > > >
> > > > so the SIZEOF_EXPR leaked into the middle end.
> > > >
> > > > (There's still one *walk_subtrees = 0; in cp_fold_immediate_r, but that
> > > > one should be OK.)
> > > >
> > > > PR c++/112869
> > > >
> > > > gcc/cp/ChangeLog:
> > > >
> > > > * cp-gimplify.cc (cp_fold_immediate_r): Don't clear *walk_subtrees
> > > > for unevaluated operands.
> > >
> > > I agree that we want this change for in_immediate_context (), but I don't
> > > see why we want it for TYPE_P or unevaluated_p (code) or
> > > cp_unevaluated_operand?
> >
> > No particular reason, just paranoia. How's this?
> >
> > Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
> >
> > -- >8 --
> > This test shows that we cannot clear *walk_subtrees in
> > cp_fold_immediate_r when we're in_immediate_context, because that,
> > as the comment says, affects cp_fold_r as well. Here we had an
> > expression with
> >
> > min ((long int) VIEW_CONVERT_EXPR<long unsigned int>(bytecount), (long int) <<< Unknown tree: sizeof_expr
> > (int) <<< error >>> >>>)
> >
> > as its sub-expression, and we never evaluated that into
> >
> > min ((long int) bytecount, 4)
> >
> > so the SIZEOF_EXPR leaked into the middle end.
> >
> > (There's still one *walk_subtrees = 0; in cp_fold_immediate_r, but that
> > one should be OK.)
> >
> > PR c++/112869
> >
> > gcc/cp/ChangeLog:
> >
> > * cp-gimplify.cc (cp_fold_immediate_r): Don't clear *walk_subtrees
> > for in_immediate_context.
> >
> > gcc/testsuite/ChangeLog:
> >
> > * g++.dg/template/sizeof18.C: New test.
> > ---
> > gcc/cp/cp-gimplify.cc | 6 +++++-
> > gcc/testsuite/g++.dg/template/sizeof18.C | 8 ++++++++
> > 2 files changed, 13 insertions(+), 1 deletion(-)
> > create mode 100644 gcc/testsuite/g++.dg/template/sizeof18.C
> >
> > diff --git a/gcc/cp/cp-gimplify.cc b/gcc/cp/cp-gimplify.cc
> > index 5abb91bbdd3..6af7c787372 100644
> > --- a/gcc/cp/cp-gimplify.cc
> > +++ b/gcc/cp/cp-gimplify.cc
> > @@ -1179,11 +1179,15 @@ cp_fold_immediate_r (tree *stmt_p, int *walk_subtrees, void *data_)
> > /* No need to look into types or unevaluated operands.
> > NB: This affects cp_fold_r as well. */
> > - if (TYPE_P (stmt) || unevaluated_p (code) || in_immediate_context ())
> > + if (TYPE_P (stmt) || unevaluated_p (code))
> > {
> > *walk_subtrees = 0;
> > return NULL_TREE;
> > }
> > + else if (in_immediate_context ())
> > + /* Don't clear *walk_subtrees here: we still need to walk the subtrees
> > + of SIZEOF_EXPR and similar. */
> > + return NULL_TREE;
> > tree decl = NULL_TREE;
> > bool call_p = false;
> > diff --git a/gcc/testsuite/g++.dg/template/sizeof18.C b/gcc/testsuite/g++.dg/template/sizeof18.C
> > new file mode 100644
> > index 00000000000..afba9946258
> > --- /dev/null
> > +++ b/gcc/testsuite/g++.dg/template/sizeof18.C
> > @@ -0,0 +1,8 @@
> > +// PR c++/112869
> > +// { dg-do compile }
> > +
> > +void min(long, long);
> > +template <class T> void Binaryread(int &, T, unsigned long);
> > +template <> void Binaryread(int &, float, unsigned long bytecount) {
> > + min(bytecount, sizeof(int));
> > +}
>
> Hmm, actually, why does the above make a difference for this testcase?
>
> ...
>
> It seems that in_immediate_context always returns true in cp_fold_function
> because current_binding_level->kind == sk_template_parms. That seems like a
> problem. Maybe for cp_fold_immediate_r we only want to check
> cp_unevaluated_operand or DECL_IMMEDIATE_CONTEXT (current_function_decl)?
Yeah, I suppose that could become an issue. How about this, then?
Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
-- >8 --
This test shows that we cannot clear *walk_subtrees in
cp_fold_immediate_r when we're in_immediate_context, because that,
as the comment says, affects cp_fold_r as well. Here we had an
expression with
min ((long int) VIEW_CONVERT_EXPR<long unsigned int>(bytecount), (long int) <<< Unknown tree: sizeof_expr
(int) <<< error >>> >>>)
as its sub-expression, and we never evaluated that into
min ((long int) bytecount, 4)
so the SIZEOF_EXPR leaked into the middle end.
(There's still one *walk_subtrees = 0; in cp_fold_immediate_r, but that
one should be OK.)
PR c++/112869
gcc/cp/ChangeLog:
* cp-gimplify.cc (cp_fold_immediate_r): Don't clear *walk_subtrees
in an unevaluated operand or immediate function.
gcc/testsuite/ChangeLog:
* g++.dg/template/sizeof18.C: New test.
---
gcc/cp/cp-gimplify.cc | 8 +++++++-
gcc/testsuite/g++.dg/template/sizeof18.C | 8 ++++++++
2 files changed, 15 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/g++.dg/template/sizeof18.C
base-commit: cd7d0b4cf789264cd75ab7df5df232dc58061ed7
Comments
On 12/12/23 17:48, Marek Polacek wrote:
> On Fri, Dec 08, 2023 at 11:09:15PM -0500, Jason Merrill wrote:
>> On 12/8/23 16:15, Marek Polacek wrote:
>>> On Fri, Dec 08, 2023 at 12:09:18PM -0500, Jason Merrill wrote:
>>>> On 12/5/23 15:31, Marek Polacek wrote:
>>>>> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
>>>>>
>>>>> -- >8 --
>>>>> This test shows that we cannot clear *walk_subtrees in
>>>>> cp_fold_immediate_r when we're in_immediate_context, because that,
>>>>> as the comment says, affects cp_fold_r as well. Here we had an
>>>>> expression with
>>>>>
>>>>> min ((long int) VIEW_CONVERT_EXPR<long unsigned int>(bytecount), (long int) <<< Unknown tree: sizeof_expr
>>>>> (int) <<< error >>> >>>)
>>>>>
>>>>> as its sub-expression, and we never evaluated that into
>>>>>
>>>>> min ((long int) bytecount, 4)
>>>>>
>>>>> so the SIZEOF_EXPR leaked into the middle end.
>>>>>
>>>>> (There's still one *walk_subtrees = 0; in cp_fold_immediate_r, but that
>>>>> one should be OK.)
>>>>>
>>>>> PR c++/112869
>>>>>
>>>>> gcc/cp/ChangeLog:
>>>>>
>>>>> * cp-gimplify.cc (cp_fold_immediate_r): Don't clear *walk_subtrees
>>>>> for unevaluated operands.
>>>>
>>>> I agree that we want this change for in_immediate_context (), but I don't
>>>> see why we want it for TYPE_P or unevaluated_p (code) or
>>>> cp_unevaluated_operand?
>>>
>>> No particular reason, just paranoia. How's this?
>>>
>>> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
>>>
>>> -- >8 --
>>> This test shows that we cannot clear *walk_subtrees in
>>> cp_fold_immediate_r when we're in_immediate_context, because that,
>>> as the comment says, affects cp_fold_r as well. Here we had an
>>> expression with
>>>
>>> min ((long int) VIEW_CONVERT_EXPR<long unsigned int>(bytecount), (long int) <<< Unknown tree: sizeof_expr
>>> (int) <<< error >>> >>>)
>>>
>>> as its sub-expression, and we never evaluated that into
>>>
>>> min ((long int) bytecount, 4)
>>>
>>> so the SIZEOF_EXPR leaked into the middle end.
>>>
>>> (There's still one *walk_subtrees = 0; in cp_fold_immediate_r, but that
>>> one should be OK.)
>>>
>>> PR c++/112869
>>>
>>> gcc/cp/ChangeLog:
>>>
>>> * cp-gimplify.cc (cp_fold_immediate_r): Don't clear *walk_subtrees
>>> for in_immediate_context.
>>>
>>> gcc/testsuite/ChangeLog:
>>>
>>> * g++.dg/template/sizeof18.C: New test.
>>> ---
>>> gcc/cp/cp-gimplify.cc | 6 +++++-
>>> gcc/testsuite/g++.dg/template/sizeof18.C | 8 ++++++++
>>> 2 files changed, 13 insertions(+), 1 deletion(-)
>>> create mode 100644 gcc/testsuite/g++.dg/template/sizeof18.C
>>>
>>> diff --git a/gcc/cp/cp-gimplify.cc b/gcc/cp/cp-gimplify.cc
>>> index 5abb91bbdd3..6af7c787372 100644
>>> --- a/gcc/cp/cp-gimplify.cc
>>> +++ b/gcc/cp/cp-gimplify.cc
>>> @@ -1179,11 +1179,15 @@ cp_fold_immediate_r (tree *stmt_p, int *walk_subtrees, void *data_)
>>> /* No need to look into types or unevaluated operands.
>>> NB: This affects cp_fold_r as well. */
>>> - if (TYPE_P (stmt) || unevaluated_p (code) || in_immediate_context ())
>>> + if (TYPE_P (stmt) || unevaluated_p (code))
>>> {
>>> *walk_subtrees = 0;
>>> return NULL_TREE;
>>> }
>>> + else if (in_immediate_context ())
>>> + /* Don't clear *walk_subtrees here: we still need to walk the subtrees
>>> + of SIZEOF_EXPR and similar. */
>>> + return NULL_TREE;
>>> tree decl = NULL_TREE;
>>> bool call_p = false;
>>> diff --git a/gcc/testsuite/g++.dg/template/sizeof18.C b/gcc/testsuite/g++.dg/template/sizeof18.C
>>> new file mode 100644
>>> index 00000000000..afba9946258
>>> --- /dev/null
>>> +++ b/gcc/testsuite/g++.dg/template/sizeof18.C
>>> @@ -0,0 +1,8 @@
>>> +// PR c++/112869
>>> +// { dg-do compile }
>>> +
>>> +void min(long, long);
>>> +template <class T> void Binaryread(int &, T, unsigned long);
>>> +template <> void Binaryread(int &, float, unsigned long bytecount) {
>>> + min(bytecount, sizeof(int));
>>> +}
>>
>> Hmm, actually, why does the above make a difference for this testcase?
>>
>> ...
>>
>> It seems that in_immediate_context always returns true in cp_fold_function
>> because current_binding_level->kind == sk_template_parms. That seems like a
>> problem. Maybe for cp_fold_immediate_r we only want to check
>> cp_unevaluated_operand or DECL_IMMEDIATE_CONTEXT (current_function_decl)?
>
> Yeah, I suppose that could become an issue. How about this, then?
>
> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
> -- >8 --
> This test shows that we cannot clear *walk_subtrees in
> cp_fold_immediate_r when we're in_immediate_context, because that,
> as the comment says, affects cp_fold_r as well. Here we had an
> expression with
>
> min ((long int) VIEW_CONVERT_EXPR<long unsigned int>(bytecount), (long int) <<< Unknown tree: sizeof_expr
> (int) <<< error >>> >>>)
>
> as its sub-expression, and we never evaluated that into
>
> min ((long int) bytecount, 4)
>
> so the SIZEOF_EXPR leaked into the middle end.
>
> (There's still one *walk_subtrees = 0; in cp_fold_immediate_r, but that
> one should be OK.)
>
> PR c++/112869
>
> gcc/cp/ChangeLog:
>
> * cp-gimplify.cc (cp_fold_immediate_r): Don't clear *walk_subtrees
> in an unevaluated operand or immediate function.
>
> gcc/testsuite/ChangeLog:
>
> * g++.dg/template/sizeof18.C: New test.
> ---
> gcc/cp/cp-gimplify.cc | 8 +++++++-
> gcc/testsuite/g++.dg/template/sizeof18.C | 8 ++++++++
> 2 files changed, 15 insertions(+), 1 deletion(-)
> create mode 100644 gcc/testsuite/g++.dg/template/sizeof18.C
>
> diff --git a/gcc/cp/cp-gimplify.cc b/gcc/cp/cp-gimplify.cc
> index c307e1b62db..413ebafbd1a 100644
> --- a/gcc/cp/cp-gimplify.cc
> +++ b/gcc/cp/cp-gimplify.cc
> @@ -1179,11 +1179,17 @@ cp_fold_immediate_r (tree *stmt_p, int *walk_subtrees, void *data_)
>
> /* No need to look into types or unevaluated operands.
> NB: This affects cp_fold_r as well. */
> - if (TYPE_P (stmt) || unevaluated_p (code) || in_immediate_context ())
> + if (TYPE_P (stmt) || unevaluated_p (code))
> {
> *walk_subtrees = 0;
> return NULL_TREE;
> }
> + else if (cp_unevaluated_operand
> + || (current_function_decl
> + && DECL_IMMEDIATE_FUNCTION_P (current_function_decl)))
It should still be fine to clear *walk_subtrees in these cases; the
problem I was talking about above was that in_immediate_context was
returning true for all functions, not just consteval functions.
I think the fix is not adding an else, but rather replacing the
in_immediate_context call with "unevaluated or consteval cfun".
> + /* Don't clear *walk_subtrees here: we still need to walk the subtrees
> + of SIZEOF_EXPR and similar. */
We shouldn't need to walk subtrees of SIZEOF_EXPR or other unevaluated
operands, they'll all get cp_folded away. The bug was that we weren't
calling cp_fold on the SIZEOF_EXPR itself.
Jason
@@ -1179,11 +1179,17 @@ cp_fold_immediate_r (tree *stmt_p, int *walk_subtrees, void *data_)
/* No need to look into types or unevaluated operands.
NB: This affects cp_fold_r as well. */
- if (TYPE_P (stmt) || unevaluated_p (code) || in_immediate_context ())
+ if (TYPE_P (stmt) || unevaluated_p (code))
{
*walk_subtrees = 0;
return NULL_TREE;
}
+ else if (cp_unevaluated_operand
+ || (current_function_decl
+ && DECL_IMMEDIATE_FUNCTION_P (current_function_decl)))
+ /* Don't clear *walk_subtrees here: we still need to walk the subtrees
+ of SIZEOF_EXPR and similar. */
+ return NULL_TREE;
tree decl = NULL_TREE;
bool call_p = false;
new file mode 100644
@@ -0,0 +1,8 @@
+// PR c++/112869
+// { dg-do compile }
+
+void min(long, long);
+template <class T> void Binaryread(int &, T, unsigned long);
+template <> void Binaryread(int &, float, unsigned long bytecount) {
+ min(bytecount, sizeof(int));
+}