http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53900
--- Comment #4 from Gael Guennebaud <gael.guennebaud at gmail dot com> 2012-07-10 11:09:16 UTC --- Created attachment 27770 --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=27770 Another demonstration of the issue using std::vector Note that when we declare: __attribute__((aligned(16))) float array[4]; we request GCC to give us an aligned array, and we are not telling gcc that array is aligned that is slightly different. I attached another example demonstrating the problem: a simple declaration like: std::vector<Foo> vec(5); generates unaligned arrays that are not caught by assertion because it has been removed by gcc 4.7. Outputs are as follow: $ g++-4.7 -m32 alignedassert.cpp && ./a.out ctor 0xffdc58f0 copy 0x9f72008 copy 0x9f72018 copy 0x9f72028 copy 0x9f72038 copy 0x9f72048 ctor 0xffdc5900 g++-4.6 -m32 alignedassert.cpp && ./a.out ctor 0xff8e19e0 copy 0x98e2008 a.out: alignedassert.cpp:18: Foo::Foo(const Foo&): Assertion `(std::ptrdiff_t(array) % std::ptrdiff_t(16))==0' failed. Aborted
