c++: fix array cleanup with throwing temp dtor

While working on PR66139 I noticed that if the destructor of a temporary
created during array initialization throws, we were failing to destroy the
last array element constructed.  Throwing destructors are rare since C++11,
but this should be fixed.

gcc/cp/ChangeLog:

	* init.c (build_vec_init): Append the decrement to elt_init.

gcc/testsuite/ChangeLog:

	* g++.dg/eh/array2.C: New test.

1 files changed, 43 insertions, 0 deletions

diff --git a/gcc/testsuite/g++.dg/eh/array2.C b/gcc/testsuite/g++.dg/eh/array2.C
new file mode 100644
index 0000000..d4d6c91
--- /dev/null
+++ b/gcc/testsuite/g++.dg/eh/array2.C
@@ -0,0 +1,43 @@
+// Test that we clean up the right number of array elements when
+// a temporary destructor throws.
+// { dg-do run }
+
+#if __cplusplus > 201100L
+#define THROWING noexcept(false)
+#else
+#define THROWING
+#endif
+
+extern "C" void abort ();
+
+int b;
+int d = -1;
+struct A {
+  A() { }
+  A(const A&);
+  ~A() THROWING {
+    if (b == d) throw b;
+  }
+};
+struct B {
+  B(const A& = A()) { ++b; }
+  B(const B&);
+  ~B() { --b; }
+};
+void f()
+{
+  b = 0;
+  try
+    {
+      B bs[3];
+      if (b != 3) abort ();
+    }
+  catch (int i) { }
+  if (b != 0) abort ();
+}
+
+int main()
+{
+  for (d = 0; d <= 3; ++d)
+    f();
+}