c++: Fix value-init crash in template [PR93676]
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Message ID 20200211195459.358172-1-polacek@redhat.com
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  • c++: Fix value-init crash in template [PR93676]
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Marek Polacek Feb. 11, 2020, 7:54 p.m. UTC
Since <https://gcc.gnu.org/ml/gcc-patches/2015-02/msg00556.html> we
attempt to value-initialize in build_vec_init even when there's no
initializer but the type has a constexpr default constructor.  But
build_value_init doesn't work in templates, so I think let's avoid
this scenario; we'll go to the normal build_aggr_init path then.

Bootstrapped/regtested on x86_64-linux, ok for trunk and branches?

	PR c++/93676 - value-init crash in template.
	* init.c (build_vec_init): Don't perform value-init in a template.

	* g++.dg/cpp0x/nsdmi-template19.C: New test.
---
 gcc/cp/init.c                                 |  2 +-
 gcc/testsuite/g++.dg/cpp0x/nsdmi-template19.C | 13 +++++++++++++
 2 files changed, 14 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/g++.dg/cpp0x/nsdmi-template19.C


base-commit: 7a775242ea296849a34ce27de179eaaec411e880

Comments

Jason Merrill Feb. 13, 2020, 11:24 p.m. UTC | #1
On 2/11/20 8:54 PM, Marek Polacek wrote:
> Since <https://gcc.gnu.org/ml/gcc-patches/2015-02/msg00556.html> we
> attempt to value-initialize in build_vec_init even when there's no
> initializer but the type has a constexpr default constructor.  But
> build_value_init doesn't work in templates, so I think let's avoid
> this scenario; we'll go to the normal build_aggr_init path then.
> 
> Bootstrapped/regtested on x86_64-linux, ok for trunk and branches?
> 
> 	PR c++/93676 - value-init crash in template.
> 	* init.c (build_vec_init): Don't perform value-init in a template.

Hmm, we really shouldn't even be calling build_vec_init in a template, 
that builds up a lot of garbage that we'll throw away at the end of 
build_new.

Jason
Marek Polacek Feb. 19, 2020, 9:15 p.m. UTC | #2
On Fri, Feb 14, 2020 at 12:24:30AM +0100, Jason Merrill wrote:
> On 2/11/20 8:54 PM, Marek Polacek wrote:
> > Since <https://gcc.gnu.org/ml/gcc-patches/2015-02/msg00556.html> we
> > attempt to value-initialize in build_vec_init even when there's no
> > initializer but the type has a constexpr default constructor.  But
> > build_value_init doesn't work in templates, so I think let's avoid
> > this scenario; we'll go to the normal build_aggr_init path then.
> > 
> > Bootstrapped/regtested on x86_64-linux, ok for trunk and branches?
> > 
> > 	PR c++/93676 - value-init crash in template.
> > 	* init.c (build_vec_init): Don't perform value-init in a template.
> 
> Hmm, we really shouldn't even be calling build_vec_init in a template, that
> builds up a lot of garbage that we'll throw away at the end of build_new.

Ah, it's true that build_new will just creates a NEW_EXPR in a template and
doesn't use the result of build_new_1.  Unfortunately I can't just call
build_special_member_call like we do in build_new_1 since that crashes for
array types.  Maybe just return NULL_TREE then?  I was afraid we would miss
diagnostics but it seems to work.

Bootstrapped/regtested on x86_64-linux, ok for trunk?

-- >8 --
Since <https://gcc.gnu.org/ml/gcc-patches/2015-02/msg00556.html> we
attempt to value-initialize in build_vec_init even when there's no
initializer but the type has a constexpr default constructor.  But
build_value_init doesn't work in templates, and build_vec_init
creates a lot of garbage that would not be used anyway, so don't
call it in a template.

	PR c++/93676 - value-init crash in template.
	* init.c (build_new_1): Don't call build_vec_init in a template.

	* g++.dg/cpp0x/nsdmi-template19.C: New test.
---
 gcc/cp/init.c                                 |  6 ++++++
 gcc/testsuite/g++.dg/cpp0x/nsdmi-template19.C | 13 +++++++++++++
 2 files changed, 19 insertions(+)
 create mode 100644 gcc/testsuite/g++.dg/cpp0x/nsdmi-template19.C

diff --git a/gcc/cp/init.c b/gcc/cp/init.c
index d480660445e..332a9b04679 100644
--- a/gcc/cp/init.c
+++ b/gcc/cp/init.c
@@ -3554,6 +3554,12 @@ build_new_1 (vec<tree, va_gc> **placement, tree type, tree nelts,
                 error ("parenthesized initializer in array new");
 	      return error_mark_node;
             }
+	  /* We shouldn't call build_vec_init in a template: it could call
+	     build_value_init which doesn't work in templates, and it would
+	     create a lot of garbage that would not be used anyway, so return
+	     a null tree and let build_new create a NEW_EXPR instead.  */
+	  if (processing_template_decl)
+	    return NULL_TREE;
 	  init_expr
 	    = build_vec_init (data_addr,
 			      cp_build_binary_op (input_location,
diff --git a/gcc/testsuite/g++.dg/cpp0x/nsdmi-template19.C b/gcc/testsuite/g++.dg/cpp0x/nsdmi-template19.C
new file mode 100644
index 00000000000..f3e2cb87fd6
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/nsdmi-template19.C
@@ -0,0 +1,13 @@
+// PR c++/93676 - value-init crash in template.
+// { dg-do compile { target c++11 } }
+
+struct P {
+  int x = 0;
+};
+
+template<class T>
+struct S {
+  S() { new P[2][2]; }
+};
+
+S<int> s;

base-commit: 58f2e59ad36ca05444cb0a57ad1f13cc58e52755
Jason Merrill Feb. 20, 2020, 12:13 a.m. UTC | #3
On 2/19/20 10:15 PM, Marek Polacek wrote:
> On Fri, Feb 14, 2020 at 12:24:30AM +0100, Jason Merrill wrote:
>> On 2/11/20 8:54 PM, Marek Polacek wrote:
>>> Since <https://gcc.gnu.org/ml/gcc-patches/2015-02/msg00556.html> we
>>> attempt to value-initialize in build_vec_init even when there's no
>>> initializer but the type has a constexpr default constructor.  But
>>> build_value_init doesn't work in templates, so I think let's avoid
>>> this scenario; we'll go to the normal build_aggr_init path then.
>>>
>>> Bootstrapped/regtested on x86_64-linux, ok for trunk and branches?
>>>
>>> 	PR c++/93676 - value-init crash in template.
>>> 	* init.c (build_vec_init): Don't perform value-init in a template.
>>
>> Hmm, we really shouldn't even be calling build_vec_init in a template, that
>> builds up a lot of garbage that we'll throw away at the end of build_new.
> 
> Ah, it's true that build_new will just creates a NEW_EXPR in a template and
> doesn't use the result of build_new_1.  Unfortunately I can't just call
> build_special_member_call like we do in build_new_1 since that crashes for
> array types.

We should call it for strip_array_types (type).

Jason
Marek Polacek Feb. 20, 2020, 4:52 p.m. UTC | #4
On Thu, Feb 20, 2020 at 12:13:07AM +0000, Jason Merrill wrote:
> On 2/19/20 10:15 PM, Marek Polacek wrote:
> > On Fri, Feb 14, 2020 at 12:24:30AM +0100, Jason Merrill wrote:
> > > On 2/11/20 8:54 PM, Marek Polacek wrote:
> > > > Since <https://gcc.gnu.org/ml/gcc-patches/2015-02/msg00556.html> we
> > > > attempt to value-initialize in build_vec_init even when there's no
> > > > initializer but the type has a constexpr default constructor.  But
> > > > build_value_init doesn't work in templates, so I think let's avoid
> > > > this scenario; we'll go to the normal build_aggr_init path then.
> > > > 
> > > > Bootstrapped/regtested on x86_64-linux, ok for trunk and branches?
> > > > 
> > > > 	PR c++/93676 - value-init crash in template.
> > > > 	* init.c (build_vec_init): Don't perform value-init in a template.
> > > 
> > > Hmm, we really shouldn't even be calling build_vec_init in a template, that
> > > builds up a lot of garbage that we'll throw away at the end of build_new.
> > 
> > Ah, it's true that build_new will just creates a NEW_EXPR in a template and
> > doesn't use the result of build_new_1.  Unfortunately I can't just call
> > build_special_member_call like we do in build_new_1 since that crashes for
> > array types.
> 
> We should call it for strip_array_types (type).

Since build_special_member_call takes an expression we'd have to modify
its type which I think is not pretty, but it works.  Is this along the
lines you had in mind?

I think I still like the v1 patch best but if you're fine with the
following, then am I.

-- >8 --
Since <https://gcc.gnu.org/ml/gcc-patches/2015-02/msg00556.html> we
attempt to value-initialize in build_vec_init even when there's no
initializer but the type has a constexpr default constructor.  But
build_value_init doesn't work in templates, and build_vec_init
creates a lot of garbage that would not be used anyway, so don't
call it in a template.

	PR c++/93676 - value-init crash in template.
	* init.c (build_new_1): Don't call build_vec_init in a template.

	* g++.dg/cpp0x/nsdmi-template19.C: New test.
---
 gcc/cp/init.c                                 |  6 +++++-
 gcc/testsuite/g++.dg/cpp0x/nsdmi-template19.C | 13 +++++++++++++
 2 files changed, 18 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/g++.dg/cpp0x/nsdmi-template19.C

diff --git a/gcc/cp/init.c b/gcc/cp/init.c
index d480660445e..c60f332313a 100644
--- a/gcc/cp/init.c
+++ b/gcc/cp/init.c
@@ -3511,13 +3511,17 @@ build_new_1 (vec<tree, va_gc> **placement, tree type, tree nelts,
 	  explicit_value_init_p = true;
 	}
 
-      if (processing_template_decl && explicit_value_init_p)
+      if (processing_template_decl)
 	{
 	  /* build_value_init doesn't work in templates, and we don't need
 	     the initializer anyway since we're going to throw it away and
 	     rebuild it at instantiation time, so just build up a single
 	     constructor call to get any appropriate diagnostics.  */
 	  init_expr = cp_build_fold_indirect_ref (data_addr);
+	  /* Avoid an ICE when converting to a base in build_simple_base_path.
+	     We'll throw this all away anyway, and build_new will create
+	     a NEW_EXPR.  */
+	  TREE_TYPE (init_expr) = strip_array_types (TREE_TYPE (init_expr));
 	  if (type_build_ctor_call (elt_type))
 	    init_expr = build_special_member_call (init_expr,
 						   complete_ctor_identifier,
diff --git a/gcc/testsuite/g++.dg/cpp0x/nsdmi-template19.C b/gcc/testsuite/g++.dg/cpp0x/nsdmi-template19.C
new file mode 100644
index 00000000000..f3e2cb87fd6
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/nsdmi-template19.C
@@ -0,0 +1,13 @@
+// PR c++/93676 - value-init crash in template.
+// { dg-do compile { target c++11 } }
+
+struct P {
+  int x = 0;
+};
+
+template<class T>
+struct S {
+  S() { new P[2][2]; }
+};
+
+S<int> s;

base-commit: 4be779f59b04947324889b7e1488fb9a68c81d53
Jason Merrill Feb. 24, 2020, 10:15 p.m. UTC | #5
On 2/20/20 11:52 AM, Marek Polacek wrote:
> On Thu, Feb 20, 2020 at 12:13:07AM +0000, Jason Merrill wrote:
>> On 2/19/20 10:15 PM, Marek Polacek wrote:
>>> On Fri, Feb 14, 2020 at 12:24:30AM +0100, Jason Merrill wrote:
>>>> On 2/11/20 8:54 PM, Marek Polacek wrote:
>>>>> Since <https://gcc.gnu.org/ml/gcc-patches/2015-02/msg00556.html> we
>>>>> attempt to value-initialize in build_vec_init even when there's no
>>>>> initializer but the type has a constexpr default constructor.  But
>>>>> build_value_init doesn't work in templates, so I think let's avoid
>>>>> this scenario; we'll go to the normal build_aggr_init path then.
>>>>>
>>>>> Bootstrapped/regtested on x86_64-linux, ok for trunk and branches?
>>>>>
>>>>> 	PR c++/93676 - value-init crash in template.
>>>>> 	* init.c (build_vec_init): Don't perform value-init in a template.
>>>>
>>>> Hmm, we really shouldn't even be calling build_vec_init in a template, that
>>>> builds up a lot of garbage that we'll throw away at the end of build_new.
>>>
>>> Ah, it's true that build_new will just creates a NEW_EXPR in a template and
>>> doesn't use the result of build_new_1.  Unfortunately I can't just call
>>> build_special_member_call like we do in build_new_1 since that crashes for
>>> array types.
>>
>> We should call it for strip_array_types (type).
> 
> Since build_special_member_call takes an expression we'd have to modify
> its type which I think is not pretty, but it works.  Is this along the
> lines you had in mind?



> I think I still like the v1 patch best but if you're fine with the
> following, then am I.
> 
> -- >8 --
> Since <https://gcc.gnu.org/ml/gcc-patches/2015-02/msg00556.html> we
> attempt to value-initialize in build_vec_init even when there's no
> initializer but the type has a constexpr default constructor.  But
> build_value_init doesn't work in templates, and build_vec_init
> creates a lot of garbage that would not be used anyway, so don't
> call it in a template.
> 
> 	PR c++/93676 - value-init crash in template.
> 	* init.c (build_new_1): Don't call build_vec_init in a template.
> 
> 	* g++.dg/cpp0x/nsdmi-template19.C: New test.
> ---
>   gcc/cp/init.c                                 |  6 +++++-
>   gcc/testsuite/g++.dg/cpp0x/nsdmi-template19.C | 13 +++++++++++++
>   2 files changed, 18 insertions(+), 1 deletion(-)
>   create mode 100644 gcc/testsuite/g++.dg/cpp0x/nsdmi-template19.C
> 
> diff --git a/gcc/cp/init.c b/gcc/cp/init.c
> index d480660445e..c60f332313a 100644
> --- a/gcc/cp/init.c
> +++ b/gcc/cp/init.c
> @@ -3511,13 +3511,17 @@ build_new_1 (vec<tree, va_gc> **placement, tree type, tree nelts,
>   	  explicit_value_init_p = true;
>   	}
>   
> -      if (processing_template_decl && explicit_value_init_p)
> +      if (processing_template_decl)
>   	{
>   	  /* build_value_init doesn't work in templates, and we don't need
>   	     the initializer anyway since we're going to throw it away and
>   	     rebuild it at instantiation time, so just build up a single
>   	     constructor call to get any appropriate diagnostics.  */
>   	  init_expr = cp_build_fold_indirect_ref (data_addr);
> +	  /* Avoid an ICE when converting to a base in build_simple_base_path.
> +	     We'll throw this all away anyway, and build_new will create
> +	     a NEW_EXPR.  */
> +	  TREE_TYPE (init_expr) = strip_array_types (TREE_TYPE (init_expr));

instead of this, how about casting data_addr to elt_type* before 
cp_build_fold_indirect_ref?

Jason
Marek Polacek Feb. 25, 2020, 5:52 p.m. UTC | #6
On Mon, Feb 24, 2020 at 05:15:45PM -0500, Jason Merrill wrote:
> On 2/20/20 11:52 AM, Marek Polacek wrote:
> > On Thu, Feb 20, 2020 at 12:13:07AM +0000, Jason Merrill wrote:
> > > On 2/19/20 10:15 PM, Marek Polacek wrote:
> > > > On Fri, Feb 14, 2020 at 12:24:30AM +0100, Jason Merrill wrote:
> > > > > On 2/11/20 8:54 PM, Marek Polacek wrote:
> > > > > > Since <https://gcc.gnu.org/ml/gcc-patches/2015-02/msg00556.html> we
> > > > > > attempt to value-initialize in build_vec_init even when there's no
> > > > > > initializer but the type has a constexpr default constructor.  But
> > > > > > build_value_init doesn't work in templates, so I think let's avoid
> > > > > > this scenario; we'll go to the normal build_aggr_init path then.
> > > > > > 
> > > > > > Bootstrapped/regtested on x86_64-linux, ok for trunk and branches?
> > > > > > 
> > > > > > 	PR c++/93676 - value-init crash in template.
> > > > > > 	* init.c (build_vec_init): Don't perform value-init in a template.
> > > > > 
> > > > > Hmm, we really shouldn't even be calling build_vec_init in a template, that
> > > > > builds up a lot of garbage that we'll throw away at the end of build_new.
> > > > 
> > > > Ah, it's true that build_new will just creates a NEW_EXPR in a template and
> > > > doesn't use the result of build_new_1.  Unfortunately I can't just call
> > > > build_special_member_call like we do in build_new_1 since that crashes for
> > > > array types.
> > > 
> > > We should call it for strip_array_types (type).
> > 
> > Since build_special_member_call takes an expression we'd have to modify
> > its type which I think is not pretty, but it works.  Is this along the
> > lines you had in mind?
> 
> 
> 
> > I think I still like the v1 patch best but if you're fine with the
> > following, then am I.
> > 
> > -- >8 --
> > Since <https://gcc.gnu.org/ml/gcc-patches/2015-02/msg00556.html> we
> > attempt to value-initialize in build_vec_init even when there's no
> > initializer but the type has a constexpr default constructor.  But
> > build_value_init doesn't work in templates, and build_vec_init
> > creates a lot of garbage that would not be used anyway, so don't
> > call it in a template.
> > 
> > 	PR c++/93676 - value-init crash in template.
> > 	* init.c (build_new_1): Don't call build_vec_init in a template.
> > 
> > 	* g++.dg/cpp0x/nsdmi-template19.C: New test.
> > ---
> >   gcc/cp/init.c                                 |  6 +++++-
> >   gcc/testsuite/g++.dg/cpp0x/nsdmi-template19.C | 13 +++++++++++++
> >   2 files changed, 18 insertions(+), 1 deletion(-)
> >   create mode 100644 gcc/testsuite/g++.dg/cpp0x/nsdmi-template19.C
> > 
> > diff --git a/gcc/cp/init.c b/gcc/cp/init.c
> > index d480660445e..c60f332313a 100644
> > --- a/gcc/cp/init.c
> > +++ b/gcc/cp/init.c
> > @@ -3511,13 +3511,17 @@ build_new_1 (vec<tree, va_gc> **placement, tree type, tree nelts,
> >   	  explicit_value_init_p = true;
> >   	}
> > -      if (processing_template_decl && explicit_value_init_p)
> > +      if (processing_template_decl)
> >   	{
> >   	  /* build_value_init doesn't work in templates, and we don't need
> >   	     the initializer anyway since we're going to throw it away and
> >   	     rebuild it at instantiation time, so just build up a single
> >   	     constructor call to get any appropriate diagnostics.  */
> >   	  init_expr = cp_build_fold_indirect_ref (data_addr);
> > +	  /* Avoid an ICE when converting to a base in build_simple_base_path.
> > +	     We'll throw this all away anyway, and build_new will create
> > +	     a NEW_EXPR.  */
> > +	  TREE_TYPE (init_expr) = strip_array_types (TREE_TYPE (init_expr));
> 
> instead of this, how about casting data_addr to elt_type* before
> cp_build_fold_indirect_ref?

That seems to work, thanks!

Bootstrapped/regtested on x86_64-linux, ok for trunk?

-- >8 --
Since <https://gcc.gnu.org/ml/gcc-patches/2015-02/msg00556.html> we
attempt to value-initialize in build_vec_init even when there's no
initializer but the type has a constexpr default constructor.  But
build_value_init doesn't work in templates, and build_vec_init
creates a lot of garbage that would not be used anyway, so don't
call it in a template.

	PR c++/93676 - value-init crash in template.
	* init.c (build_new_1): Don't call build_vec_init in a template.

	* g++.dg/cpp0x/nsdmi-template19.C: New test.
---
 gcc/cp/init.c                                 |  6 +++++-
 gcc/testsuite/g++.dg/cpp0x/nsdmi-template19.C | 13 +++++++++++++
 2 files changed, 18 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/g++.dg/cpp0x/nsdmi-template19.C

diff --git a/gcc/cp/init.c b/gcc/cp/init.c
index d480660445e..31a130422af 100644
--- a/gcc/cp/init.c
+++ b/gcc/cp/init.c
@@ -3511,8 +3511,12 @@ build_new_1 (vec<tree, va_gc> **placement, tree type, tree nelts,
 	  explicit_value_init_p = true;
 	}
 
-      if (processing_template_decl && explicit_value_init_p)
+      if (processing_template_decl)
 	{
+	  /* Avoid an ICE when converting to a base in build_simple_base_path.
+	     We'll throw this all away anyway, and build_new will create
+	     a NEW_EXPR.  */
+	  data_addr = build_nop (build_pointer_type (elt_type), data_addr);
 	  /* build_value_init doesn't work in templates, and we don't need
 	     the initializer anyway since we're going to throw it away and
 	     rebuild it at instantiation time, so just build up a single
diff --git a/gcc/testsuite/g++.dg/cpp0x/nsdmi-template19.C b/gcc/testsuite/g++.dg/cpp0x/nsdmi-template19.C
new file mode 100644
index 00000000000..f3e2cb87fd6
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/nsdmi-template19.C
@@ -0,0 +1,13 @@
+// PR c++/93676 - value-init crash in template.
+// { dg-do compile { target c++11 } }
+
+struct P {
+  int x = 0;
+};
+
+template<class T>
+struct S {
+  S() { new P[2][2]; }
+};
+
+S<int> s;

base-commit: a71f2193d0df71a86c4743aab22891bb0003112e
Jason Merrill Feb. 25, 2020, 6:27 p.m. UTC | #7
On 2/25/20 12:52 PM, Marek Polacek wrote:
> On Mon, Feb 24, 2020 at 05:15:45PM -0500, Jason Merrill wrote:
>> On 2/20/20 11:52 AM, Marek Polacek wrote:
>>> On Thu, Feb 20, 2020 at 12:13:07AM +0000, Jason Merrill wrote:
>>>> On 2/19/20 10:15 PM, Marek Polacek wrote:
>>>>> On Fri, Feb 14, 2020 at 12:24:30AM +0100, Jason Merrill wrote:
>>>>>> On 2/11/20 8:54 PM, Marek Polacek wrote:
>>>>>>> Since <https://gcc.gnu.org/ml/gcc-patches/2015-02/msg00556.html> we
>>>>>>> attempt to value-initialize in build_vec_init even when there's no
>>>>>>> initializer but the type has a constexpr default constructor.  But
>>>>>>> build_value_init doesn't work in templates, so I think let's avoid
>>>>>>> this scenario; we'll go to the normal build_aggr_init path then.
>>>>>>>
>>>>>>> Bootstrapped/regtested on x86_64-linux, ok for trunk and branches?
>>>>>>>
>>>>>>> 	PR c++/93676 - value-init crash in template.
>>>>>>> 	* init.c (build_vec_init): Don't perform value-init in a template.
>>>>>>
>>>>>> Hmm, we really shouldn't even be calling build_vec_init in a template, that
>>>>>> builds up a lot of garbage that we'll throw away at the end of build_new.
>>>>>
>>>>> Ah, it's true that build_new will just creates a NEW_EXPR in a template and
>>>>> doesn't use the result of build_new_1.  Unfortunately I can't just call
>>>>> build_special_member_call like we do in build_new_1 since that crashes for
>>>>> array types.
>>>>
>>>> We should call it for strip_array_types (type).
>>>
>>> Since build_special_member_call takes an expression we'd have to modify
>>> its type which I think is not pretty, but it works.  Is this along the
>>> lines you had in mind?
>>
>>
>>
>>> I think I still like the v1 patch best but if you're fine with the
>>> following, then am I.
>>>
>>> -- >8 --
>>> Since <https://gcc.gnu.org/ml/gcc-patches/2015-02/msg00556.html> we
>>> attempt to value-initialize in build_vec_init even when there's no
>>> initializer but the type has a constexpr default constructor.  But
>>> build_value_init doesn't work in templates, and build_vec_init
>>> creates a lot of garbage that would not be used anyway, so don't
>>> call it in a template.
>>>
>>> 	PR c++/93676 - value-init crash in template.
>>> 	* init.c (build_new_1): Don't call build_vec_init in a template.
>>>
>>> 	* g++.dg/cpp0x/nsdmi-template19.C: New test.
>>> ---
>>>    gcc/cp/init.c                                 |  6 +++++-
>>>    gcc/testsuite/g++.dg/cpp0x/nsdmi-template19.C | 13 +++++++++++++
>>>    2 files changed, 18 insertions(+), 1 deletion(-)
>>>    create mode 100644 gcc/testsuite/g++.dg/cpp0x/nsdmi-template19.C
>>>
>>> diff --git a/gcc/cp/init.c b/gcc/cp/init.c
>>> index d480660445e..c60f332313a 100644
>>> --- a/gcc/cp/init.c
>>> +++ b/gcc/cp/init.c
>>> @@ -3511,13 +3511,17 @@ build_new_1 (vec<tree, va_gc> **placement, tree type, tree nelts,
>>>    	  explicit_value_init_p = true;
>>>    	}
>>> -      if (processing_template_decl && explicit_value_init_p)
>>> +      if (processing_template_decl)
>>>    	{
>>>    	  /* build_value_init doesn't work in templates, and we don't need
>>>    	     the initializer anyway since we're going to throw it away and
>>>    	     rebuild it at instantiation time, so just build up a single
>>>    	     constructor call to get any appropriate diagnostics.  */
>>>    	  init_expr = cp_build_fold_indirect_ref (data_addr);
>>> +	  /* Avoid an ICE when converting to a base in build_simple_base_path.
>>> +	     We'll throw this all away anyway, and build_new will create
>>> +	     a NEW_EXPR.  */
>>> +	  TREE_TYPE (init_expr) = strip_array_types (TREE_TYPE (init_expr));
>>
>> instead of this, how about casting data_addr to elt_type* before
>> cp_build_fold_indirect_ref?
> 
> That seems to work, thanks!
> 
> Bootstrapped/regtested on x86_64-linux, ok for trunk?
> 
> -- >8 --
> Since <https://gcc.gnu.org/ml/gcc-patches/2015-02/msg00556.html> we
> attempt to value-initialize in build_vec_init even when there's no
> initializer but the type has a constexpr default constructor.  But
> build_value_init doesn't work in templates, and build_vec_init
> creates a lot of garbage that would not be used anyway, so don't
> call it in a template.
> 
> 	PR c++/93676 - value-init crash in template.
> 	* init.c (build_new_1): Don't call build_vec_init in a template.
> 
> 	* g++.dg/cpp0x/nsdmi-template19.C: New test.
> ---
>   gcc/cp/init.c                                 |  6 +++++-
>   gcc/testsuite/g++.dg/cpp0x/nsdmi-template19.C | 13 +++++++++++++
>   2 files changed, 18 insertions(+), 1 deletion(-)
>   create mode 100644 gcc/testsuite/g++.dg/cpp0x/nsdmi-template19.C
> 
> diff --git a/gcc/cp/init.c b/gcc/cp/init.c
> index d480660445e..31a130422af 100644
> --- a/gcc/cp/init.c
> +++ b/gcc/cp/init.c
> @@ -3511,8 +3511,12 @@ build_new_1 (vec<tree, va_gc> **placement, tree type, tree nelts,
>   	  explicit_value_init_p = true;
>   	}
>   
> -      if (processing_template_decl && explicit_value_init_p)
> +      if (processing_template_decl)
>   	{
> +	  /* Avoid an ICE when converting to a base in build_simple_base_path.
> +	     We'll throw this all away anyway, and build_new will create
> +	     a NEW_EXPR.  */
> +	  data_addr = build_nop (build_pointer_type (elt_type), data_addr);

Let's use a new local variable instead of changing data_addr, which 
following code expects to still have its old type.

And as a minor tweak, data_addr might already have the right type, so 
let's use fold_convert like other places in the function.

>   	  /* build_value_init doesn't work in templates, and we don't need
>   	     the initializer anyway since we're going to throw it away and
>   	     rebuild it at instantiation time, so just build up a single
> diff --git a/gcc/testsuite/g++.dg/cpp0x/nsdmi-template19.C b/gcc/testsuite/g++.dg/cpp0x/nsdmi-template19.C
> new file mode 100644
> index 00000000000..f3e2cb87fd6
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp0x/nsdmi-template19.C
> @@ -0,0 +1,13 @@
> +// PR c++/93676 - value-init crash in template.
> +// { dg-do compile { target c++11 } }
> +
> +struct P {
> +  int x = 0;
> +};
> +
> +template<class T>
> +struct S {
> +  S() { new P[2][2]; }
> +};
> +
> +S<int> s;
> 
> base-commit: a71f2193d0df71a86c4743aab22891bb0003112e
>
Marek Polacek Feb. 25, 2020, 6:55 p.m. UTC | #8
On Tue, Feb 25, 2020 at 01:27:12PM -0500, Jason Merrill wrote:
> On 2/25/20 12:52 PM, Marek Polacek wrote:
> > On Mon, Feb 24, 2020 at 05:15:45PM -0500, Jason Merrill wrote:
> > > On 2/20/20 11:52 AM, Marek Polacek wrote:
> > > > On Thu, Feb 20, 2020 at 12:13:07AM +0000, Jason Merrill wrote:
> > > > > On 2/19/20 10:15 PM, Marek Polacek wrote:
> > > > > > On Fri, Feb 14, 2020 at 12:24:30AM +0100, Jason Merrill wrote:
> > > > > > > On 2/11/20 8:54 PM, Marek Polacek wrote:
> > > > > > > > Since <https://gcc.gnu.org/ml/gcc-patches/2015-02/msg00556.html> we
> > > > > > > > attempt to value-initialize in build_vec_init even when there's no
> > > > > > > > initializer but the type has a constexpr default constructor.  But
> > > > > > > > build_value_init doesn't work in templates, so I think let's avoid
> > > > > > > > this scenario; we'll go to the normal build_aggr_init path then.
> > > > > > > > 
> > > > > > > > Bootstrapped/regtested on x86_64-linux, ok for trunk and branches?
> > > > > > > > 
> > > > > > > > 	PR c++/93676 - value-init crash in template.
> > > > > > > > 	* init.c (build_vec_init): Don't perform value-init in a template.
> > > > > > > 
> > > > > > > Hmm, we really shouldn't even be calling build_vec_init in a template, that
> > > > > > > builds up a lot of garbage that we'll throw away at the end of build_new.
> > > > > > 
> > > > > > Ah, it's true that build_new will just creates a NEW_EXPR in a template and
> > > > > > doesn't use the result of build_new_1.  Unfortunately I can't just call
> > > > > > build_special_member_call like we do in build_new_1 since that crashes for
> > > > > > array types.
> > > > > 
> > > > > We should call it for strip_array_types (type).
> > > > 
> > > > Since build_special_member_call takes an expression we'd have to modify
> > > > its type which I think is not pretty, but it works.  Is this along the
> > > > lines you had in mind?
> > > 
> > > 
> > > 
> > > > I think I still like the v1 patch best but if you're fine with the
> > > > following, then am I.
> > > > 
> > > > -- >8 --
> > > > Since <https://gcc.gnu.org/ml/gcc-patches/2015-02/msg00556.html> we
> > > > attempt to value-initialize in build_vec_init even when there's no
> > > > initializer but the type has a constexpr default constructor.  But
> > > > build_value_init doesn't work in templates, and build_vec_init
> > > > creates a lot of garbage that would not be used anyway, so don't
> > > > call it in a template.
> > > > 
> > > > 	PR c++/93676 - value-init crash in template.
> > > > 	* init.c (build_new_1): Don't call build_vec_init in a template.
> > > > 
> > > > 	* g++.dg/cpp0x/nsdmi-template19.C: New test.
> > > > ---
> > > >    gcc/cp/init.c                                 |  6 +++++-
> > > >    gcc/testsuite/g++.dg/cpp0x/nsdmi-template19.C | 13 +++++++++++++
> > > >    2 files changed, 18 insertions(+), 1 deletion(-)
> > > >    create mode 100644 gcc/testsuite/g++.dg/cpp0x/nsdmi-template19.C
> > > > 
> > > > diff --git a/gcc/cp/init.c b/gcc/cp/init.c
> > > > index d480660445e..c60f332313a 100644
> > > > --- a/gcc/cp/init.c
> > > > +++ b/gcc/cp/init.c
> > > > @@ -3511,13 +3511,17 @@ build_new_1 (vec<tree, va_gc> **placement, tree type, tree nelts,
> > > >    	  explicit_value_init_p = true;
> > > >    	}
> > > > -      if (processing_template_decl && explicit_value_init_p)
> > > > +      if (processing_template_decl)
> > > >    	{
> > > >    	  /* build_value_init doesn't work in templates, and we don't need
> > > >    	     the initializer anyway since we're going to throw it away and
> > > >    	     rebuild it at instantiation time, so just build up a single
> > > >    	     constructor call to get any appropriate diagnostics.  */
> > > >    	  init_expr = cp_build_fold_indirect_ref (data_addr);
> > > > +	  /* Avoid an ICE when converting to a base in build_simple_base_path.
> > > > +	     We'll throw this all away anyway, and build_new will create
> > > > +	     a NEW_EXPR.  */
> > > > +	  TREE_TYPE (init_expr) = strip_array_types (TREE_TYPE (init_expr));
> > > 
> > > instead of this, how about casting data_addr to elt_type* before
> > > cp_build_fold_indirect_ref?

Gotcha.  I'm testing the following, OK for 8/9/10 if it passes?

-- >8 --
Since <https://gcc.gnu.org/ml/gcc-patches/2015-02/msg00556.html> we
attempt to value-initialize in build_vec_init even when there's no
initializer but the type has a constexpr default constructor.  But
build_value_init doesn't work in templates, and build_vec_init
creates a lot of garbage that would not be used anyway, so don't
call it in a template.

	PR c++/93676 - value-init crash in template.
	* init.c (build_new_1): Don't call build_vec_init in a template.

	* g++.dg/cpp0x/nsdmi-template19.C: New test.
---
 gcc/cp/init.c                                 |  8 ++++++--
 gcc/testsuite/g++.dg/cpp0x/nsdmi-template19.C | 13 +++++++++++++
 2 files changed, 19 insertions(+), 2 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/cpp0x/nsdmi-template19.C

diff --git a/gcc/cp/init.c b/gcc/cp/init.c
index d480660445e..61ed3aa7e93 100644
--- a/gcc/cp/init.c
+++ b/gcc/cp/init.c
@@ -3511,13 +3511,17 @@ build_new_1 (vec<tree, va_gc> **placement, tree type, tree nelts,
 	  explicit_value_init_p = true;
 	}
 
-      if (processing_template_decl && explicit_value_init_p)
+      if (processing_template_decl)
 	{
+	  /* Avoid an ICE when converting to a base in build_simple_base_path.
+	     We'll throw this all away anyway, and build_new will create
+	     a NEW_EXPR.  */
+	  tree t = fold_convert (build_pointer_type (elt_type), data_addr);
 	  /* build_value_init doesn't work in templates, and we don't need
 	     the initializer anyway since we're going to throw it away and
 	     rebuild it at instantiation time, so just build up a single
 	     constructor call to get any appropriate diagnostics.  */
-	  init_expr = cp_build_fold_indirect_ref (data_addr);
+	  init_expr = cp_build_fold_indirect_ref (t);
 	  if (type_build_ctor_call (elt_type))
 	    init_expr = build_special_member_call (init_expr,
 						   complete_ctor_identifier,
diff --git a/gcc/testsuite/g++.dg/cpp0x/nsdmi-template19.C b/gcc/testsuite/g++.dg/cpp0x/nsdmi-template19.C
new file mode 100644
index 00000000000..f3e2cb87fd6
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/nsdmi-template19.C
@@ -0,0 +1,13 @@
+// PR c++/93676 - value-init crash in template.
+// { dg-do compile { target c++11 } }
+
+struct P {
+  int x = 0;
+};
+
+template<class T>
+struct S {
+  S() { new P[2][2]; }
+};
+
+S<int> s;

base-commit: a71f2193d0df71a86c4743aab22891bb0003112e
Marek Polacek Feb. 25, 2020, 7:34 p.m. UTC | #9
On Tue, Feb 25, 2020 at 01:55:24PM -0500, Marek Polacek wrote:
> On Tue, Feb 25, 2020 at 01:27:12PM -0500, Jason Merrill wrote:
> > On 2/25/20 12:52 PM, Marek Polacek wrote:
> > > On Mon, Feb 24, 2020 at 05:15:45PM -0500, Jason Merrill wrote:
> > > > On 2/20/20 11:52 AM, Marek Polacek wrote:
> > > > > On Thu, Feb 20, 2020 at 12:13:07AM +0000, Jason Merrill wrote:
> > > > > > On 2/19/20 10:15 PM, Marek Polacek wrote:
> > > > > > > On Fri, Feb 14, 2020 at 12:24:30AM +0100, Jason Merrill wrote:
> > > > > > > > On 2/11/20 8:54 PM, Marek Polacek wrote:
> > > > > > > > > Since <https://gcc.gnu.org/ml/gcc-patches/2015-02/msg00556.html> we
> > > > > > > > > attempt to value-initialize in build_vec_init even when there's no
> > > > > > > > > initializer but the type has a constexpr default constructor.  But
> > > > > > > > > build_value_init doesn't work in templates, so I think let's avoid
> > > > > > > > > this scenario; we'll go to the normal build_aggr_init path then.
> > > > > > > > > 
> > > > > > > > > Bootstrapped/regtested on x86_64-linux, ok for trunk and branches?
> > > > > > > > > 
> > > > > > > > > 	PR c++/93676 - value-init crash in template.
> > > > > > > > > 	* init.c (build_vec_init): Don't perform value-init in a template.
> > > > > > > > 
> > > > > > > > Hmm, we really shouldn't even be calling build_vec_init in a template, that
> > > > > > > > builds up a lot of garbage that we'll throw away at the end of build_new.
> > > > > > > 
> > > > > > > Ah, it's true that build_new will just creates a NEW_EXPR in a template and
> > > > > > > doesn't use the result of build_new_1.  Unfortunately I can't just call
> > > > > > > build_special_member_call like we do in build_new_1 since that crashes for
> > > > > > > array types.
> > > > > > 
> > > > > > We should call it for strip_array_types (type).
> > > > > 
> > > > > Since build_special_member_call takes an expression we'd have to modify
> > > > > its type which I think is not pretty, but it works.  Is this along the
> > > > > lines you had in mind?
> > > > 
> > > > 
> > > > 
> > > > > I think I still like the v1 patch best but if you're fine with the
> > > > > following, then am I.
> > > > > 
> > > > > -- >8 --
> > > > > Since <https://gcc.gnu.org/ml/gcc-patches/2015-02/msg00556.html> we
> > > > > attempt to value-initialize in build_vec_init even when there's no
> > > > > initializer but the type has a constexpr default constructor.  But
> > > > > build_value_init doesn't work in templates, and build_vec_init
> > > > > creates a lot of garbage that would not be used anyway, so don't
> > > > > call it in a template.
> > > > > 
> > > > > 	PR c++/93676 - value-init crash in template.
> > > > > 	* init.c (build_new_1): Don't call build_vec_init in a template.
> > > > > 
> > > > > 	* g++.dg/cpp0x/nsdmi-template19.C: New test.
> > > > > ---
> > > > >    gcc/cp/init.c                                 |  6 +++++-
> > > > >    gcc/testsuite/g++.dg/cpp0x/nsdmi-template19.C | 13 +++++++++++++
> > > > >    2 files changed, 18 insertions(+), 1 deletion(-)
> > > > >    create mode 100644 gcc/testsuite/g++.dg/cpp0x/nsdmi-template19.C
> > > > > 
> > > > > diff --git a/gcc/cp/init.c b/gcc/cp/init.c
> > > > > index d480660445e..c60f332313a 100644
> > > > > --- a/gcc/cp/init.c
> > > > > +++ b/gcc/cp/init.c
> > > > > @@ -3511,13 +3511,17 @@ build_new_1 (vec<tree, va_gc> **placement, tree type, tree nelts,
> > > > >    	  explicit_value_init_p = true;
> > > > >    	}
> > > > > -      if (processing_template_decl && explicit_value_init_p)
> > > > > +      if (processing_template_decl)
> > > > >    	{
> > > > >    	  /* build_value_init doesn't work in templates, and we don't need
> > > > >    	     the initializer anyway since we're going to throw it away and
> > > > >    	     rebuild it at instantiation time, so just build up a single
> > > > >    	     constructor call to get any appropriate diagnostics.  */
> > > > >    	  init_expr = cp_build_fold_indirect_ref (data_addr);
> > > > > +	  /* Avoid an ICE when converting to a base in build_simple_base_path.
> > > > > +	     We'll throw this all away anyway, and build_new will create
> > > > > +	     a NEW_EXPR.  */
> > > > > +	  TREE_TYPE (init_expr) = strip_array_types (TREE_TYPE (init_expr));
> > > > 
> > > > instead of this, how about casting data_addr to elt_type* before
> > > > cp_build_fold_indirect_ref?
> 
> Gotcha.  I'm testing the following, OK for 8/9/10 if it passes?

Which it did.

> -- >8 --
> Since <https://gcc.gnu.org/ml/gcc-patches/2015-02/msg00556.html> we
> attempt to value-initialize in build_vec_init even when there's no
> initializer but the type has a constexpr default constructor.  But
> build_value_init doesn't work in templates, and build_vec_init
> creates a lot of garbage that would not be used anyway, so don't
> call it in a template.
> 
> 	PR c++/93676 - value-init crash in template.
> 	* init.c (build_new_1): Don't call build_vec_init in a template.
> 
> 	* g++.dg/cpp0x/nsdmi-template19.C: New test.
> ---
>  gcc/cp/init.c                                 |  8 ++++++--
>  gcc/testsuite/g++.dg/cpp0x/nsdmi-template19.C | 13 +++++++++++++
>  2 files changed, 19 insertions(+), 2 deletions(-)
>  create mode 100644 gcc/testsuite/g++.dg/cpp0x/nsdmi-template19.C
> 
> diff --git a/gcc/cp/init.c b/gcc/cp/init.c
> index d480660445e..61ed3aa7e93 100644
> --- a/gcc/cp/init.c
> +++ b/gcc/cp/init.c
> @@ -3511,13 +3511,17 @@ build_new_1 (vec<tree, va_gc> **placement, tree type, tree nelts,
>  	  explicit_value_init_p = true;
>  	}
>  
> -      if (processing_template_decl && explicit_value_init_p)
> +      if (processing_template_decl)
>  	{
> +	  /* Avoid an ICE when converting to a base in build_simple_base_path.
> +	     We'll throw this all away anyway, and build_new will create
> +	     a NEW_EXPR.  */
> +	  tree t = fold_convert (build_pointer_type (elt_type), data_addr);
>  	  /* build_value_init doesn't work in templates, and we don't need
>  	     the initializer anyway since we're going to throw it away and
>  	     rebuild it at instantiation time, so just build up a single
>  	     constructor call to get any appropriate diagnostics.  */
> -	  init_expr = cp_build_fold_indirect_ref (data_addr);
> +	  init_expr = cp_build_fold_indirect_ref (t);
>  	  if (type_build_ctor_call (elt_type))
>  	    init_expr = build_special_member_call (init_expr,
>  						   complete_ctor_identifier,
> diff --git a/gcc/testsuite/g++.dg/cpp0x/nsdmi-template19.C b/gcc/testsuite/g++.dg/cpp0x/nsdmi-template19.C
> new file mode 100644
> index 00000000000..f3e2cb87fd6
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp0x/nsdmi-template19.C
> @@ -0,0 +1,13 @@
> +// PR c++/93676 - value-init crash in template.
> +// { dg-do compile { target c++11 } }
> +
> +struct P {
> +  int x = 0;
> +};
> +
> +template<class T>
> +struct S {
> +  S() { new P[2][2]; }
> +};
> +
> +S<int> s;
> 
> base-commit: a71f2193d0df71a86c4743aab22891bb0003112e
> -- 
> Marek Polacek • Red Hat, Inc. • 300 A St, Boston, MA
> 

Marek
Jason Merrill Feb. 26, 2020, 4:26 a.m. UTC | #10
On 2/25/20 1:55 PM, Marek Polacek wrote:
> On Tue, Feb 25, 2020 at 01:27:12PM -0500, Jason Merrill wrote:
>> On 2/25/20 12:52 PM, Marek Polacek wrote:
>>> On Mon, Feb 24, 2020 at 05:15:45PM -0500, Jason Merrill wrote:
>>>> On 2/20/20 11:52 AM, Marek Polacek wrote:
>>>>> On Thu, Feb 20, 2020 at 12:13:07AM +0000, Jason Merrill wrote:
>>>>>> On 2/19/20 10:15 PM, Marek Polacek wrote:
>>>>>>> On Fri, Feb 14, 2020 at 12:24:30AM +0100, Jason Merrill wrote:
>>>>>>>> On 2/11/20 8:54 PM, Marek Polacek wrote:
>>>>>>>>> Since <https://gcc.gnu.org/ml/gcc-patches/2015-02/msg00556.html> we
>>>>>>>>> attempt to value-initialize in build_vec_init even when there's no
>>>>>>>>> initializer but the type has a constexpr default constructor.  But
>>>>>>>>> build_value_init doesn't work in templates, so I think let's avoid
>>>>>>>>> this scenario; we'll go to the normal build_aggr_init path then.
>>>>>>>>>
>>>>>>>>> Bootstrapped/regtested on x86_64-linux, ok for trunk and branches?
>>>>>>>>>
>>>>>>>>> 	PR c++/93676 - value-init crash in template.
>>>>>>>>> 	* init.c (build_vec_init): Don't perform value-init in a template.
>>>>>>>>
>>>>>>>> Hmm, we really shouldn't even be calling build_vec_init in a template, that
>>>>>>>> builds up a lot of garbage that we'll throw away at the end of build_new.
>>>>>>>
>>>>>>> Ah, it's true that build_new will just creates a NEW_EXPR in a template and
>>>>>>> doesn't use the result of build_new_1.  Unfortunately I can't just call
>>>>>>> build_special_member_call like we do in build_new_1 since that crashes for
>>>>>>> array types.
>>>>>>
>>>>>> We should call it for strip_array_types (type).
>>>>>
>>>>> Since build_special_member_call takes an expression we'd have to modify
>>>>> its type which I think is not pretty, but it works.  Is this along the
>>>>> lines you had in mind?
>>>>
>>>>
>>>>
>>>>> I think I still like the v1 patch best but if you're fine with the
>>>>> following, then am I.
>>>>>
>>>>> -- >8 --
>>>>> Since <https://gcc.gnu.org/ml/gcc-patches/2015-02/msg00556.html> we
>>>>> attempt to value-initialize in build_vec_init even when there's no
>>>>> initializer but the type has a constexpr default constructor.  But
>>>>> build_value_init doesn't work in templates, and build_vec_init
>>>>> creates a lot of garbage that would not be used anyway, so don't
>>>>> call it in a template.
>>>>>
>>>>> 	PR c++/93676 - value-init crash in template.
>>>>> 	* init.c (build_new_1): Don't call build_vec_init in a template.
>>>>>
>>>>> 	* g++.dg/cpp0x/nsdmi-template19.C: New test.
>>>>> ---
>>>>>     gcc/cp/init.c                                 |  6 +++++-
>>>>>     gcc/testsuite/g++.dg/cpp0x/nsdmi-template19.C | 13 +++++++++++++
>>>>>     2 files changed, 18 insertions(+), 1 deletion(-)
>>>>>     create mode 100644 gcc/testsuite/g++.dg/cpp0x/nsdmi-template19.C
>>>>>
>>>>> diff --git a/gcc/cp/init.c b/gcc/cp/init.c
>>>>> index d480660445e..c60f332313a 100644
>>>>> --- a/gcc/cp/init.c
>>>>> +++ b/gcc/cp/init.c
>>>>> @@ -3511,13 +3511,17 @@ build_new_1 (vec<tree, va_gc> **placement, tree type, tree nelts,
>>>>>     	  explicit_value_init_p = true;
>>>>>     	}
>>>>> -      if (processing_template_decl && explicit_value_init_p)
>>>>> +      if (processing_template_decl)
>>>>>     	{
>>>>>     	  /* build_value_init doesn't work in templates, and we don't need
>>>>>     	     the initializer anyway since we're going to throw it away and
>>>>>     	     rebuild it at instantiation time, so just build up a single
>>>>>     	     constructor call to get any appropriate diagnostics.  */
>>>>>     	  init_expr = cp_build_fold_indirect_ref (data_addr);
>>>>> +	  /* Avoid an ICE when converting to a base in build_simple_base_path.
>>>>> +	     We'll throw this all away anyway, and build_new will create
>>>>> +	     a NEW_EXPR.  */
>>>>> +	  TREE_TYPE (init_expr) = strip_array_types (TREE_TYPE (init_expr));
>>>>
>>>> instead of this, how about casting data_addr to elt_type* before
>>>> cp_build_fold_indirect_ref?
> 
> Gotcha.  I'm testing the following, OK for 8/9/10 if it passes?

OK.

> 
> -- >8 --
> Since <https://gcc.gnu.org/ml/gcc-patches/2015-02/msg00556.html> we
> attempt to value-initialize in build_vec_init even when there's no
> initializer but the type has a constexpr default constructor.  But
> build_value_init doesn't work in templates, and build_vec_init
> creates a lot of garbage that would not be used anyway, so don't
> call it in a template.
> 
> 	PR c++/93676 - value-init crash in template.
> 	* init.c (build_new_1): Don't call build_vec_init in a template.
> 
> 	* g++.dg/cpp0x/nsdmi-template19.C: New test.
> ---
>   gcc/cp/init.c                                 |  8 ++++++--
>   gcc/testsuite/g++.dg/cpp0x/nsdmi-template19.C | 13 +++++++++++++
>   2 files changed, 19 insertions(+), 2 deletions(-)
>   create mode 100644 gcc/testsuite/g++.dg/cpp0x/nsdmi-template19.C
> 
> diff --git a/gcc/cp/init.c b/gcc/cp/init.c
> index d480660445e..61ed3aa7e93 100644
> --- a/gcc/cp/init.c
> +++ b/gcc/cp/init.c
> @@ -3511,13 +3511,17 @@ build_new_1 (vec<tree, va_gc> **placement, tree type, tree nelts,
>   	  explicit_value_init_p = true;
>   	}
>   
> -      if (processing_template_decl && explicit_value_init_p)
> +      if (processing_template_decl)
>   	{
> +	  /* Avoid an ICE when converting to a base in build_simple_base_path.
> +	     We'll throw this all away anyway, and build_new will create
> +	     a NEW_EXPR.  */
> +	  tree t = fold_convert (build_pointer_type (elt_type), data_addr);
>   	  /* build_value_init doesn't work in templates, and we don't need
>   	     the initializer anyway since we're going to throw it away and
>   	     rebuild it at instantiation time, so just build up a single
>   	     constructor call to get any appropriate diagnostics.  */
> -	  init_expr = cp_build_fold_indirect_ref (data_addr);
> +	  init_expr = cp_build_fold_indirect_ref (t);
>   	  if (type_build_ctor_call (elt_type))
>   	    init_expr = build_special_member_call (init_expr,
>   						   complete_ctor_identifier,
> diff --git a/gcc/testsuite/g++.dg/cpp0x/nsdmi-template19.C b/gcc/testsuite/g++.dg/cpp0x/nsdmi-template19.C
> new file mode 100644
> index 00000000000..f3e2cb87fd6
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp0x/nsdmi-template19.C
> @@ -0,0 +1,13 @@
> +// PR c++/93676 - value-init crash in template.
> +// { dg-do compile { target c++11 } }
> +
> +struct P {
> +  int x = 0;
> +};
> +
> +template<class T>
> +struct S {
> +  S() { new P[2][2]; }
> +};
> +
> +S<int> s;
> 
> base-commit: a71f2193d0df71a86c4743aab22891bb0003112e
>

Patch
diff mbox series

diff --git a/gcc/cp/init.c b/gcc/cp/init.c
index d480660445e..c9c0f03c58b 100644
--- a/gcc/cp/init.c
+++ b/gcc/cp/init.c
@@ -4520,7 +4520,7 @@  build_vec_init (tree base, tree maxindex, tree init,
 
      We do need to keep going if we're copying an array.  */
 
-  if (try_const && !init)
+  if (try_const && !init && !processing_template_decl)
     /* With a constexpr default constructor, which we checked for when
        setting try_const above, default-initialization is equivalent to
        value-initialization, and build_value_init gives us something more
diff --git a/gcc/testsuite/g++.dg/cpp0x/nsdmi-template19.C b/gcc/testsuite/g++.dg/cpp0x/nsdmi-template19.C
new file mode 100644
index 00000000000..f3e2cb87fd6
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/nsdmi-template19.C
@@ -0,0 +1,13 @@ 
+// PR c++/93676 - value-init crash in template.
+// { dg-do compile { target c++11 } }
+
+struct P {
+  int x = 0;
+};
+
+template<class T>
+struct S {
+  S() { new P[2][2]; }
+};
+
+S<int> s;