warn if class type has alignment greater than "new" provides and doesn't overload operator new

[llvmbot]

Bugzilla Link	9527
Resolution	FIXED
Resolved on	Jan 24, 2012 15:16
Version	trunk
OS	Linux
Reporter	LLVM Bugzilla Contributor

Extended Description

I'd like a new warning that fires whenever a class has alignment that is larger than that provided by the operator new, and doesn't provide its own operator new. We could make it -Wobject-alignment=16 and off by default.

Sample:

class Test {
template
struct SeparateCacheLines {
T data;
} attribute((aligned(64)));

SeparateCacheLines<int> high_contention_data[10];

};

I'd like a warning that fires on class Test, "class Test can not be heap allocated". It should not fire if operator new is overloaded. It should not fire on SeparateCacheLines<> itself.

[llvmbot]

-Wover-aligned added in r148857. Unlike the original request, this only fires on places that actually attempt to construct such an object with the default allocator.