From: Marek Polacek <polacek@redhat.com>
Date: Tue, 2 Jul 2024 19:22:39 +0000 (-0400)
Subject: c++: array new with value-initialization [PR115645]
X-Git-Tag: basepoints/gcc-16~7607
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=fde96e8205f343e6471a11cc9def967bb5dd5362;p=thirdparty%2Fgcc.git

c++: array new with value-initialization [PR115645]

This extends the r11-5179 fix which doesn't work with multidimensional
arrays.  In particular,

  struct S {
    explicit S() { }
  };
  auto p = new S[1][1]();

should not say "converting to S from initializer list would use
explicit constructor" because there's no {}.  However, since we
went into the block where we create a {}, we got confused.  We
should not have gotten there but we did because array_p was true.

This patch refines the check once more.

	PR c++/115645

gcc/cp/ChangeLog:

	* init.cc (build_new): Don't do any deduction for arrays with
	bounds if it's value-initialized.

gcc/testsuite/ChangeLog:

	* g++.dg/expr/anew7.C: New test.
---

diff --git a/gcc/cp/init.cc b/gcc/cp/init.cc
index 826a31c4a84..e9561c146d7 100644
--- a/gcc/cp/init.cc
+++ b/gcc/cp/init.cc
@@ -4005,10 +4005,14 @@ 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
-      /* 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 ())))
+      /* If the array didn't specify its bound, we have to deduce it.  */
+      && ((array_p && !TYPE_DOMAIN (type))
+	  /* For C++20 array with parenthesized-init, we have to process
+	     the parenthesized-list.  But don't do it for (), which is
+	     value-initialization, and INIT should stay empty.  */
+	  || (cxx_dialect >= cxx20
+	      && (array_p || nelts)
+	      && !(*init)->is_empty ())))
     {
       /* This means we have 'new T[]()'.  */
       if ((*init)->is_empty ())
diff --git a/gcc/testsuite/g++.dg/expr/anew7.C b/gcc/testsuite/g++.dg/expr/anew7.C
new file mode 100644
index 00000000000..ead5536e109
--- /dev/null
+++ b/gcc/testsuite/g++.dg/expr/anew7.C
@@ -0,0 +1,13 @@
+// PR c++/115645
+// { dg-do compile { target c++11 } }
+
+struct S {
+  explicit S() { }
+};
+
+auto p = new S[1][1]();
+auto q = new S[1][1]{}; // { dg-error "explicit" }
+auto r = new S[1]();
+auto s = new S[1]{}; // { dg-error "explicit" }
+auto t = new S[1][1][1]();
+auto u = new S[1][1][1]{}; // { dg-error "explicit" }