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<tree, va_gc> **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 00000000000..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 00000000000..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
