debug allocator may crash on OOM (was: tcmalloc failure memset(ptr, 0, sizeof(Object) + num*sizeof(T));)

(gdb) p ptr
$1 = (void *) 0x0
(gdb) f 0
#0 0x00007f586e642a33 in New<AddressMap::Entry> (num=64, this=0x25c8000, this=0x25c8000)

at src/addressmap-inl.h:259

259 memset(ptr, 0, sizeof(Object) + num_sizeof(T));
(gdb) l
254 // Allocates a zeroed array of T with length "num". Also inserts
255 // the allocated block into a linked list so it can be deallocated
256 // when we are all done.
257 template T_ New(int num) {
258 void* ptr = (alloc)(sizeof(Object) + num_sizeof(T));
259 memset(ptr, 0, sizeof(Object) + num_sizeof(T));
260 Object_ obj = reinterpret_cast<Object*>(ptr);
261 obj->next = allocated_;
262 allocated_ = obj;
263 return reinterpret_cast<T*>(reinterpret_cast<Object*>(ptr) + 1);
(gdb) bt
#0 0x00007f586e642a33 in New<AddressMap::Entry> (num=64, this=0x25c8000, this=0x25c8000)

at src/addressmap-inl.h:259

#1 AddressMap::Insert (this=0x25c8000, key=key@entry=0x28f606e0, value=value@entry=-21308287)

at src/addressmap-inl.h:324

#2 0x00007f586e642c56 in Initialize (type=-21308287, size=512, this=)

at src/debugallocation.cc:381

#3 Allocate (type=-21308287, size=512) at src/debugallocation.cc:535
#4 DebugAllocate (type=-21308287, size=512) at src/debugallocation.cc:987
#5 debug_cpp_alloc (size=512, new_type=-21308287, nothrow=) at src/debugallocation.cc:1106
#6 0x00007f586e65ea25 in tc_new (size=size@entry=512) at src/debugallocation.cc:1215
#7 0x00000000004107fa in allocate (__n=64, this=)

at /usr/include/c++/4.8.2/ext/new_allocator.h:104

#8 _M_allocate_node (this=) at /usr/include/c++/4.8.2/bits/stl_deque.h:533
#9 _M_create_nodes (this=0x5761ce0, __nfinish=0x286422d0, __nstart=0x286422c8)

at /usr/include/c++/4.8.2/bits/stl_deque.h:627

#10 std::_Deque_base<ctx_t*, std::allocator<ctx_t*> >::_M_initialize_map (this=this@entry=0x5761ce0,

__num_elements=__num_elements@entry=0) at /usr/include/c++/4.8.2/bits/stl_deque.h:601

so the alloc seemed to have returned nul and tcmalloc does not seem to be able to handle it.

so two things: OOM killer did not kill the process; alloc seemed to have failed with null ptr.

Start at src/addressmap-inl.h:257-262 and trace the allocation path through src/debugallocation.cc:381, 535, 987, and 1106. Reproduce or inspect the null allocation path and establish the intended out-of-memory behavior; done means allocation failure no longer reaches memset with a null pointer.