Don't allow storing types that throw in the destructor in our containers

Types that throw in their destructors are strongly discouraged in C++,
and even the STL doesn't define what happens if such types are stored
in their containers.

Make this more explicit for Qt and disallow storing those types in our
containers. This will hopefully preempty any potential future bug
reports about us not handling such a case. It also helps simplify
some code in QList and other cases and makes it possible to explicitly
mark more methods as noexcept.

Some care needs to be taken where to add the static asserts, so that
we don't disallow forward declarations of types stored in containers.
Place the static assert into the destructor of the container where
possible or otherwise into the templated d-pointer.

Change-Id: If3aa40888f668d0f1b6c6b3ad4862b169d31280e
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Andrei Golubev <andrei.golubev@qt.io>
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>

2 files changed, 2 insertions, 10 deletions

diff --git a/tests/auto/corelib/tools/collections/tst_collections.cpp b/tests/auto/corelib/tools/collections/tst_collections.cpp
index 50f9f155d0..0d4623f7fd 100644
--- a/tests/auto/corelib/tools/collections/tst_collections.cpp
+++ b/tests/auto/corelib/tools/collections/tst_collections.cpp
@@ -2920,6 +2920,7 @@ void tst_Collections::forwardDeclared()
     TEST(QVector<T1>);
     TEST(QStack<T1>);
     TEST(QQueue<T1>);
+    TEST(QSet<T1>);
 #undef TEST
 #undef COMMA
 
diff --git a/tests/auto/corelib/tools/qarraydata/tst_qarraydata.cpp b/tests/auto/corelib/tools/qarraydata/tst_qarraydata.cpp
index d82f4c4a22..9aa1b4e668 100644
--- a/tests/auto/corelib/tools/qarraydata/tst_qarraydata.cpp
+++ b/tests/auto/corelib/tools/qarraydata/tst_qarraydata.cpp
@@ -2297,7 +2297,6 @@ ThrowingTypeWatcher& throwingTypeWatcher() { static ThrowingTypeWatcher global;
 struct ThrowingType
 {
     static unsigned int throwOnce;
-    static unsigned int throwOnceInDtor;
     static constexpr char throwString[] = "Requested to throw";
     static constexpr char throwStringDtor[] = "Requested to throw in dtor";
     void checkThrow()  {
@@ -2326,22 +2325,14 @@ struct ThrowingType
         checkThrow();
         return *this;
     }
-    ~ThrowingType() noexcept(false)
+    ~ThrowingType()
     {
         throwingTypeWatcher().destroyed(id);  // notify global watcher
         id = -1;
 
-        // deferred throw
-        if (throwOnceInDtor > 0) {
-            --throwOnceInDtor;
-            if (throwOnceInDtor == 0) {
-                throw std::runtime_error(throwStringDtor);
-            }
-        }
     }
 };
 unsigned int ThrowingType::throwOnce = 0;
-unsigned int ThrowingType::throwOnceInDtor = 0;
 bool operator==(const ThrowingType &a, const ThrowingType &b) {
     return a.id == b.id;
 }