Implement P0035R4 -- Add C++17 aligned allocation functions

Summary:
This patch implements the library side of P0035R4. The implementation is thanks to @rsmith.

In addition to the C++17 implementation, the library implementation can be explicitly turned on using `-faligned-allocation` in all dialects.


Reviewers: mclow.lists, rsmith

Subscribers: rsmith, cfe-commits

Differential Revision: https://reviews.llvm.org/D25591

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@284206 91177308-0d34-0410-b5e6-96231b3b80d8

src/new.cpp

@@ -39,10 +39,7 @@
 
 _LIBCPP_WEAK _LIBCPP_NEW_DELETE_VIS
 void *
-operator new(std::size_t size)
-#if !__has_feature(cxx_noexcept)
-    throw(std::bad_alloc)
-#endif
+operator new(std::size_t size) _THROW_BAD_ALLOC
 {
     if (size == 0)
         size = 1;
@@ -64,6 +61,34 @@ operator new(std::size_t size)
     return p;
 }
 
+_LIBCPP_WEAK _LIBCPP_NEW_DELETE_VIS
+void *
+operator new(std::size_t size, std::align_val_t alignment) _THROW_BAD_ALLOC
+{
+    if (size == 0)
+        size = 1;
+    if (static_cast<size_t>(alignment) < sizeof(void*))
+      alignment = std::align_val_t(sizeof(void*));
+    void* p;
+    while (::posix_memalign(&p, static_cast<size_t>(alignment), size) != 0)
+    {
+        // If posix_memalign fails and there is a new_handler,
+        // call it to try free up memory.
+        std::new_handler nh = std::get_new_handler();
+        if (nh)
+            nh();
+        else {
+#ifndef _LIBCPP_NO_EXCEPTIONS
+            throw std::bad_alloc();
+#else
+            p = nullptr; // posix_memalign doesn't initialize 'p' on failure
+            break;
+#endif
+        }
+    }
+    return p;
+}
+
 _LIBCPP_WEAK _LIBCPP_NEW_DELETE_VIS
 void*
 operator new(size_t size, const std::nothrow_t&) _NOEXCEPT
@@ -85,14 +110,37 @@ operator new(size_t size, const std::nothrow_t&) _NOEXCEPT
 
 _LIBCPP_WEAK _LIBCPP_NEW_DELETE_VIS
 void*
-operator new[](size_t size)
-#if !__has_feature(cxx_noexcept)
-    throw(std::bad_alloc)
-#endif
+operator new(size_t size, std::align_val_t alignment, const std::nothrow_t&) _NOEXCEPT
+{
+    void* p = 0;
+#ifndef _LIBCPP_NO_EXCEPTIONS
+    try
+    {
+#endif  // _LIBCPP_NO_EXCEPTIONS
+        p = ::operator new(size, alignment);
+#ifndef _LIBCPP_NO_EXCEPTIONS
+    }
+    catch (...)
+    {
+    }
+#endif  // _LIBCPP_NO_EXCEPTIONS
+    return p;
+}
+
+_LIBCPP_WEAK _LIBCPP_NEW_DELETE_VIS
+void*
+operator new[](size_t size) _THROW_BAD_ALLOC
 {
     return ::operator new(size);
 }
 
+_LIBCPP_WEAK _LIBCPP_NEW_DELETE_VIS
+void*
+operator new[](size_t size, std::align_val_t alignment) _THROW_BAD_ALLOC
+{
+    return ::operator new(size, alignment);
+}
+
 _LIBCPP_WEAK _LIBCPP_NEW_DELETE_VIS
 void*
 operator new[](size_t size, const std::nothrow_t&) _NOEXCEPT
@@ -112,6 +160,25 @@ operator new[](size_t size, const std::nothrow_t&) _NOEXCEPT
     return p;
 }
 
+_LIBCPP_WEAK _LIBCPP_NEW_DELETE_VIS
+void*
+operator new[](size_t size, std::align_val_t alignment, const std::nothrow_t&) _NOEXCEPT
+{
+    void* p = 0;
+#ifndef _LIBCPP_NO_EXCEPTIONS
+    try
+    {
+#endif  // _LIBCPP_NO_EXCEPTIONS
+        p = ::operator new[](size, alignment);
+#ifndef _LIBCPP_NO_EXCEPTIONS
+    }
+    catch (...)
+    {
+    }
+#endif  // _LIBCPP_NO_EXCEPTIONS
+    return p;
+}
+
 _LIBCPP_WEAK _LIBCPP_NEW_DELETE_VIS
 void
 operator delete(void* ptr) _NOEXCEPT
@@ -120,6 +187,14 @@ operator delete(void* ptr) _NOEXCEPT
         ::free(ptr);
 }
 
+_LIBCPP_WEAK _LIBCPP_NEW_DELETE_VIS
+void
+operator delete(void* ptr, std::align_val_t) _NOEXCEPT
+{
+    if (ptr)
+        ::free(ptr);
+}
+
 _LIBCPP_WEAK _LIBCPP_NEW_DELETE_VIS
 void
 operator delete(void* ptr, const std::nothrow_t&) _NOEXCEPT
@@ -127,6 +202,13 @@ operator delete(void* ptr, const std::nothrow_t&) _NOEXCEPT
     ::operator delete(ptr);
 }
 
+_LIBCPP_WEAK _LIBCPP_NEW_DELETE_VIS
+void
+operator delete(void* ptr, std::align_val_t alignment, const std::nothrow_t&) _NOEXCEPT
+{
+    ::operator delete(ptr, alignment);
+}
+
 _LIBCPP_WEAK _LIBCPP_NEW_DELETE_VIS
 void
 operator delete(void* ptr, size_t) _NOEXCEPT
@@ -134,6 +216,13 @@ operator delete(void* ptr, size_t) _NOEXCEPT
     ::operator delete(ptr);
 }
 
+_LIBCPP_WEAK _LIBCPP_NEW_DELETE_VIS
+void
+operator delete(void* ptr, size_t, std::align_val_t alignment) _NOEXCEPT
+{
+    ::operator delete(ptr, alignment);
+}
+
 _LIBCPP_WEAK _LIBCPP_NEW_DELETE_VIS
 void
 operator delete[] (void* ptr) _NOEXCEPT
@@ -141,6 +230,13 @@ operator delete[] (void* ptr) _NOEXCEPT
     ::operator delete(ptr);
 }
 
+_LIBCPP_WEAK _LIBCPP_NEW_DELETE_VIS
+void
+operator delete[] (void* ptr, std::align_val_t alignment) _NOEXCEPT
+{
+    ::operator delete(ptr, alignment);
+}
+
 _LIBCPP_WEAK _LIBCPP_NEW_DELETE_VIS
 void
 operator delete[] (void* ptr, const std::nothrow_t&) _NOEXCEPT
@@ -148,6 +244,13 @@ operator delete[] (void* ptr, const std::nothrow_t&) _NOEXCEPT
     ::operator delete[](ptr);
 }
 
+_LIBCPP_WEAK _LIBCPP_NEW_DELETE_VIS
+void
+operator delete[] (void* ptr, std::align_val_t alignment, const std::nothrow_t&) _NOEXCEPT
+{
+    ::operator delete[](ptr, alignment);
+}
+
 _LIBCPP_WEAK _LIBCPP_NEW_DELETE_VIS
 void
 operator delete[] (void* ptr, size_t) _NOEXCEPT
@@ -155,6 +258,13 @@ operator delete[] (void* ptr, size_t) _NOEXCEPT
     ::operator delete[](ptr);
 }
 
+_LIBCPP_WEAK _LIBCPP_NEW_DELETE_VIS
+void
+operator delete[] (void* ptr, size_t, std::align_val_t alignment) _NOEXCEPT
+{
+    ::operator delete[](ptr, alignment);
+}
+
 #endif // !__GLIBCXX__
 
 namespace std