CI fixes (#1744)

* Fix warning that not including a cmake source or build dir will be a fatal error (it is now on newest CMakes)
    * Fixes appveyor
* Travis uses CMake 3.9 for more than a year now
* Travis dropped sudo: false in December
* Dropping Sphinx 2
- clang7: Suppress self-assign warnings; fix missing virtual dtors
- pypy:
  - Keep old version (newer stuff breaks)
  - Pin packages to extra index for speed
- travis:
  - Make docker explicit; remove docker if not needed
  - Make commands more verbose (for debugging / repro)
  - Make Ubuntu dist explicit per job
- Fix Windows
- Add names to travis

.appveyor.yml

@@ -62,6 +62,7 @@ build_script:
     -DPYBIND11_WERROR=ON
     -DDOWNLOAD_CATCH=ON
     -DCMAKE_SUPPRESS_REGENERATION=1
+    .
 - set MSBuildLogger="C:\Program Files\AppVeyor\BuildAgent\Appveyor.MSBuildLogger.dll"
 - cmake --build . --config %CONFIG% --target pytest -- /m /v:m /logger:%MSBuildLogger%
 - cmake --build . --config %CONFIG% --target cpptest -- /m /v:m /logger:%MSBuildLogger%

include/pybind11/numpy.h

@@ -1509,7 +1509,7 @@ private:
         if (trivial == broadcast_trivial::f_trivial) result = array_t<Return, array::f_style>(shape);
         else result = array_t<Return>(shape);
 
-        if (size == 0) return result;
+        if (size == 0) return std::move(result);
 
         /* Call the function */
         if (trivial == broadcast_trivial::non_trivial)
@@ -1517,7 +1517,7 @@ private:
         else
             apply_trivial(buffers, params, result.mutable_data(), size, i_seq, vi_seq, bi_seq);
 
-        return result;
+        return std::move(result);
     }
 
     template <size_t... Index, size_t... VIndex, size_t... BIndex>

tests/test_gil_scoped.cpp

@@ -13,6 +13,7 @@
 
 class VirtClass  {
 public:
+    virtual ~VirtClass() {}
     virtual void virtual_func() {}
     virtual void pure_virtual_func() = 0;
 };

tests/test_kwargs_and_defaults.cpp

@@ -34,7 +34,9 @@ TEST_SUBMODULE(kwargs_and_defaults, m) {
     m.def("kw_func_udl_z", kw_func, "x"_a, "y"_a=0);
 
     // test_args_and_kwargs
-    m.def("args_function", [](py::args args) -> py::tuple { return args; });
+    m.def("args_function", [](py::args args) -> py::tuple {
+        return std::move(args);
+    });
     m.def("args_kwargs_function", [](py::args args, py::kwargs kwargs) {
         return py::make_tuple(args, kwargs);
     });

tests/test_operator_overloading.cpp

@@ -62,6 +62,25 @@ namespace std {
     };
 }
 
+// MSVC warns about unknown pragmas, and warnings are errors.
+#ifndef _MSC_VER
+  #pragma GCC diagnostic push
+  // clang 7.0.0 and Apple LLVM 10.0.1 introduce `-Wself-assign-overloaded` to
+  // `-Wall`, which is used here for overloading (e.g. `py::self += py::self `).
+  // Here, we suppress the warning using `#pragma diagnostic`.
+  // Taken from: https://github.com/RobotLocomotion/drake/commit/aaf84b46
+  // TODO(eric): This could be resolved using a function / functor (e.g. `py::self()`).
+  #if (__APPLE__) && (__clang__)
+    #if (__clang_major__ >= 10) && (__clang_minor__ >= 0) && (__clang_patchlevel__ >= 1)
+      #pragma GCC diagnostic ignored "-Wself-assign-overloaded"
+    #endif
+  #elif (__clang__)
+    #if (__clang_major__ >= 7)
+      #pragma GCC diagnostic ignored "-Wself-assign-overloaded"
+    #endif
+  #endif
+#endif
+
 TEST_SUBMODULE(operators, m) {
 
     // test_operator_overloading
@@ -144,3 +163,7 @@ TEST_SUBMODULE(operators, m) {
         .def_readwrite("b", &NestC::b);
     m.def("get_NestC", [](const NestC &c) { return c.value; });
 }
+
+#ifndef _MSC_VER
+  #pragma GCC diagnostic pop
+#endif

tests/test_smart_ptr.cpp

@@ -336,7 +336,9 @@ TEST_SUBMODULE(smart_ptr, m) {
 
     // test_shared_ptr_gc
     // #187: issue involving std::shared_ptr<> return value policy & garbage collection
-    struct ElementBase { virtual void foo() { } /* Force creation of virtual table */ };
+    struct ElementBase {
+        virtual ~ElementBase() { } /* Force creation of virtual table */
+    };
     py::class_<ElementBase, std::shared_ptr<ElementBase>>(m, "ElementBase");
 
     struct ElementA : ElementBase {

tests/test_virtual_functions.cpp

@@ -129,6 +129,7 @@ private:
 
 class NCVirt {
 public:
+    virtual ~NCVirt() { }
     virtual NonCopyable get_noncopyable(int a, int b) { return NonCopyable(a, b); }
     virtual Movable get_movable(int a, int b) = 0;