Re: [PATCH] c++: Fix array new with value-initialization [PR97523]
On 11/19/20 11:11 AM, Marek Polacek wrote:
Since my r11-3092 the following is rejected with -std=c++20:
struct T { explicit T(); };
void fn(int n) {
new T[1]();
}
with "would use explicit constructor 'T::T()'". It is because since
that change we go into the P1009 block in build_new (array_p is false,
but nelts is non-null and we're in C++20). Since we only have (), we
build a {} and continue to build_new_1, which then calls build_vec_init
and then we error because the {} isn't CONSTRUCTOR_IS_DIRECT_INIT.
For (), which is value-initializing, we want to do what we were doing
before: pass empty init and let build_value_init take care of it.
For various reasons I wanted to dig a little bit deeper into this,
and as a result, I'm adding a test for [expr.new]/24 (and checked that
out current behavior matches clang++).
Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
OK.
gcc/cp/ChangeLog:
PR c++/97523
* init.c (build_new): When value-initializing an array new,
leave the INIT as an empty vector.
gcc/testsuite/ChangeLog:
PR c++/97523
* g++.dg/expr/anew5.C: New test.
* g++.dg/expr/anew6.C: New test.
---
gcc/cp/init.c | 6 +-
gcc/testsuite/g++.dg/expr/anew5.C | 26
gcc/testsuite/g++.dg/expr/anew6.C | 33 +++
3 files changed, 64 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/g++.dg/expr/anew5.C
create mode 100644 gcc/testsuite/g++.dg/expr/anew6.C
diff --git a/gcc/cp/init.c b/gcc/cp/init.c
index ffb84ea5b09..0b98f338feb 100644
--- a/gcc/cp/init.c
+++ b/gcc/cp/init.c
@@ -3766,7 +3766,11 @@ build_new (location_t loc, vec **placement,
tree type,
/* P1009: Array size deduction in new-expressions. */
const bool array_p = TREE_CODE (type) == ARRAY_TYPE;
- if (*init && (array_p || (nelts && cxx_dialect >= cxx20)))
+ if (*init
+ /* If ARRAY_P, we have to deduce the array bound. For C++20 paren-init,
+we have to process the parenthesized-list. But don't do it for (),
+which is value-initialization, and INIT should stay empty. */
+ && (array_p || (cxx_dialect >= cxx20 && nelts && !(*init)->is_empty (
{
/* This means we have 'new T[]()'. */
if ((*init)->is_empty ())
diff --git a/gcc/testsuite/g++.dg/expr/anew5.C
b/gcc/testsuite/g++.dg/expr/anew5.C
new file mode 100644
index 000..d597caf5483
--- /dev/null
+++ b/gcc/testsuite/g++.dg/expr/anew5.C
@@ -0,0 +1,26 @@
+// PR c++/97523
+// { dg-do compile }
+// We were turning the () into {} which made it seem like
+// aggregate-initialization (we are dealing with arrays here), which
+// performs copy-initialization, which only accepts converting constructors.
+
+struct T {
+ explicit T();
+ T(int);
+};
+
+void
+fn (int n)
+{
+ new T[1]();
+ new T[2]();
+ new T[3]();
+ new T[n]();
+#if __cpp_aggregate_paren_init
+ new T[]();
+ new T[2](1, 2);
+ // T[2] is initialized via copy-initialization, so we can't call
+ // explicit T().
+ new T[3](1, 2); // { dg-error "explicit constructor" "" { target c++20 } }
+#endif
+}
diff --git a/gcc/testsuite/g++.dg/expr/anew6.C
b/gcc/testsuite/g++.dg/expr/anew6.C
new file mode 100644
index 000..0542daac275
--- /dev/null
+++ b/gcc/testsuite/g++.dg/expr/anew6.C
@@ -0,0 +1,33 @@
+// PR c++/97523
+// { dg-do compile { target c++11 } }
+
+// [expr.new]/24: If the new-expression creates an object or an array of
+// objects of class type, access and ambiguity control are done for the
+// [...] constructor selected for the initialization (if any).
+// NB: We only check for a default constructor if the array has a non-constant
+// bound, or there are insufficient initializers. Since an array is an
+// aggregate, we perform aggregate-initialization, which performs
+// copy-initialization, so we only accept converting constructors.
+
+struct T {
+ explicit T();
+ T(int);
+};
+
+struct S {
+ S(int);
+};
+
+void
+fn (int n)
+{
+ new T[1]{}; // { dg-error "explicit constructor" }
+ new T[2]{1, 2};
+ new T[3]{1, 2}; // { dg-error "explicit constructor" }
+ new T[n]{}; // { dg-error "explicit constructor" }
+
+ new S[1]{}; // { dg-error "could not convert" }
+ new S[2]{1, 2};
+ new S[3]{1, 2}; // { dg-error "could not convert" }
+ new S[n]{}; // { dg-error "could not convert" }
+}
base-commit: 2729378d0905a04e476a8bdcaaf0288f417810ec
[PATCH] c++: Fix array new with value-initialization [PR97523]
Since my r11-3092 the following is rejected with -std=c++20:
struct T { explicit T(); };
void fn(int n) {
new T[1]();
}
with "would use explicit constructor 'T::T()'". It is because since
that change we go into the P1009 block in build_new (array_p is false,
but nelts is non-null and we're in C++20). Since we only have (), we
build a {} and continue to build_new_1, which then calls build_vec_init
and then we error because the {} isn't CONSTRUCTOR_IS_DIRECT_INIT.
For (), which is value-initializing, we want to do what we were doing
before: pass empty init and let build_value_init take care of it.
For various reasons I wanted to dig a little bit deeper into this,
and as a result, I'm adding a test for [expr.new]/24 (and checked that
out current behavior matches clang++).
Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
gcc/cp/ChangeLog:
PR c++/97523
* init.c (build_new): When value-initializing an array new,
leave the INIT as an empty vector.
gcc/testsuite/ChangeLog:
PR c++/97523
* g++.dg/expr/anew5.C: New test.
* g++.dg/expr/anew6.C: New test.
---
gcc/cp/init.c | 6 +-
gcc/testsuite/g++.dg/expr/anew5.C | 26
gcc/testsuite/g++.dg/expr/anew6.C | 33 +++
3 files changed, 64 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/g++.dg/expr/anew5.C
create mode 100644 gcc/testsuite/g++.dg/expr/anew6.C
diff --git a/gcc/cp/init.c b/gcc/cp/init.c
index ffb84ea5b09..0b98f338feb 100644
--- a/gcc/cp/init.c
+++ b/gcc/cp/init.c
@@ -3766,7 +3766,11 @@ build_new (location_t loc, vec **placement,
tree type,
/* P1009: Array size deduction in new-expressions. */
const bool array_p = TREE_CODE (type) == ARRAY_TYPE;
- if (*init && (array_p || (nelts && cxx_dialect >= cxx20)))
+ if (*init
+ /* If ARRAY_P, we have to deduce the array bound. For C++20 paren-init,
+we have to process the parenthesized-list. But don't do it for (),
+which is value-initialization, and INIT should stay empty. */
+ && (array_p || (cxx_dialect >= cxx20 && nelts && !(*init)->is_empty (
{
/* This means we have 'new T[]()'. */
if ((*init)->is_empty ())
diff --git a/gcc/testsuite/g++.dg/expr/anew5.C
b/gcc/testsuite/g++.dg/expr/anew5.C
new file mode 100644
index 000..d597caf5483
--- /dev/null
+++ b/gcc/testsuite/g++.dg/expr/anew5.C
@@ -0,0 +1,26 @@
+// PR c++/97523
+// { dg-do compile }
+// We were turning the () into {} which made it seem like
+// aggregate-initialization (we are dealing with arrays here), which
+// performs copy-initialization, which only accepts converting constructors.
+
+struct T {
+ explicit T();
+ T(int);
+};
+
+void
+fn (int n)
+{
+ new T[1]();
+ new T[2]();
+ new T[3]();
+ new T[n]();
+#if __cpp_aggregate_paren_init
+ new T[]();
+ new T[2](1, 2);
+ // T[2] is initialized via copy-initialization, so we can't call
+ // explicit T().
+ new T[3](1, 2); // { dg-error "explicit constructor" "" { target c++20 } }
+#endif
+}
diff --git a/gcc/testsuite/g++.dg/expr/anew6.C
b/gcc/testsuite/g++.dg/expr/anew6.C
new file mode 100644
index 000..0542daac275
--- /dev/null
+++ b/gcc/testsuite/g++.dg/expr/anew6.C
@@ -0,0 +1,33 @@
+// PR c++/97523
+// { dg-do compile { target c++11 } }
+
+// [expr.new]/24: If the new-expression creates an object or an array of
+// objects of class type, access and ambiguity control are done for the
+// [...] constructor selected for the initialization (if any).
+// NB: We only check for a default constructor if the array has a non-constant
+// bound, or there are insufficient initializers. Since an array is an
+// aggregate, we perform aggregate-initialization, which performs
+// copy-initialization, so we only accept converting constructors.
+
+struct T {
+ explicit T();
+ T(int);
+};
+
+struct S {
+ S(int);
+};
+
+void
+fn (int n)
+{
+ new T[1]{}; // { dg-error "explicit constructor" }
+ new T[2]{1, 2};
+ new T[3]{1, 2}; // { dg-error "explicit constructor" }
+ new T[n]{}; // { dg-error "explicit constructor" }
+
+ new S[1]{}; // { dg-error "could not convert" }
+ new S[2]{1, 2};
+ new S[3]{1, 2}; // { dg-error "could not convert" }
+ new S[n]{}; // { dg-error "could not convert" }
+}
base-commit: 2729378d0905a04e476a8bdcaaf0288f417810ec
--
2.28.0
