Aligned allocation fixes. Fixes #1845 (#1846)

The error in #1845 shows:

/<<PKGBUILDDIR>>/src/mixed_arena.h: In member function 'void* MixedArena::allocSpace(size_t, size_t)':
/<<PKGBUILDDIR>>/src/mixed_arena.h:125:43: error: 'new' of type 'MixedArena::Chunk' {aka 'std::aligned_storage<32768, 16>::type'} with extended alignment 16 [-Werror=aligned-new=]
       chunks.push_back(new Chunk[numChunks]);
                                           ^
/<<PKGBUILDDIR>>/src/mixed_arena.h:125:43: note: uses 'void* operator new [](std::size_t)', which does not have an alignment parameter
/<<PKGBUILDDIR>>/src/mixed_arena.h:125:43: note: use '-faligned-new' to enable C++17 over-aligned new support

It turns out I had misread the aligned_storage docs, and they don't actually do what we need, which is a convenient cross-platform way to do aligned allocation, since new itself doesn't support that. Sadly it seems there is no cross-platform way to do it right now, so I added a header in support which abstracts over the windows and everything-else ways.

Also add some ctest testing, which runs on windows, so we get basic windows coverage in our CI.

1 files changed, 55 insertions, 0 deletions

diff --git a/src/support/alloc.h b/src/support/alloc.h
new file mode 100644
index 000000000..86c49d2f5
--- /dev/null
+++ b/src/support/alloc.h
@@ -0,0 +1,55 @@
+/*
+ * Copyright 2019 WebAssembly Community Group participants
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+//
+// Allocation helpers
+//
+
+#ifndef wasm_support_alloc_h
+#define wasm_support_alloc_h
+
+#include <stdlib.h>
+
+#if defined(WIN32) || defined(_WIN32)
+#include <malloc.h>
+#endif
+
+namespace wasm {
+
+// An allocation of a specific size and a minimum alignment. Must be freed
+// with aligned_free. Returns nullptr on failure.
+inline void* aligned_malloc(size_t align, size_t size) {
+#if defined(WIN32) || defined(_WIN32)
+  _set_errno(0);
+  void* ret = _aligned_malloc(size, align);
+  if (errno == ENOMEM) ret = nullptr;
+  return ret;
+#else
+  return aligned_alloc(align, size);
+#endif
+}
+
+inline void aligned_free(void* ptr) {
+#if defined(WIN32) || defined(_WIN32)
+  _aligned_free(ptr);
+#else
+  free(ptr);
+#endif
+}
+
+} // namespace wasm
+
+#endif  // wasm_support_alloc_h