C++ 有几个特定的区域用来存储对象或非对象值，每个区域有其各自的特点。
https://stackoverflow.com/questions/14588767/where-in-memory-are-my-variables-stored-in-c
Global variables -------> data
Static variables -------> data
Constant data types -----> code
Local variables (declared and defined in functions) --------> stack
Variables declared and defined in main function -----> heap
Pointers (for example, char *arr, int *arr) -------> heap
Dynamically allocated space (using malloc and calloc) --------> stack
http://pierre.aubert.free.fr/divers/gotw/gotw009a.html
在C++里，通常new出来的对象时在空闲存储区里的，而malloc出来的空间则是在堆里。
空闲存储区的第一个特点时，其中分配的对象没有名字。new表达式没有返回实际分配的对象，二十返回指向该对象的指针。对该对象的全部操作都要通过这个指针间接完成。例如：
int* pi = new int;
该new表达式会创建一个int型对象，由pi指向它。
空闲存储区的第二个特点时，分配的内存未初始化。空闲存储区的内存包含随机的位模式。它是程序运行前该内存上次被使用留下的结果。
Const Data The const data area stores string literals and
other data whose values are known at compile
time. No objects of class type can exist in
this area. All data in this area is available
during the entire lifetime of the program.
常量
Further, all of this data is read-only, and the
results of trying to modify it are undefined.
This is in part because even the underlying
storage format is subject to arbitrary
optimization by the implementation. For
example, a particular compiler may store string
literals in overlapping objects if it wants to.
Stack The stack stores automatic variables. Typically
allocation is much faster than for dynamic
storage (heap or free store) because a memory
allocation involves only pointer increment
rather than more complex management. Objects
are constructed immediately after memory is
allocated and destroyed immediately before
memory is deallocated, so there is no
opportunity for programmers to directly
manipulate allocated but uninitialized stack
space (barring willful tampering using explicit
dtors and placement new).
Free Store The free store is one of the two dynamic memory
areas, allocated/freed by new/delete. Object
lifetime can be less than the time the storage
is allocated; that is, free store objects can
have memory allocated without being immediately
initialized, and can be destroyed without the
memory being immediately deallocated. During
the period when the storage is allocated but
outside the object's lifetime, the storage may
be accessed and manipulated through a void* but
none of the proto-object's nonstatic members or
member functions may be accessed, have their
addresses taken, or be otherwise manipulated.
Heap The heap is the other dynamic memory area,
allocated/freed by malloc/free and their
variants. Note that while the default global
new and delete might be implemented in terms of
malloc and free by a particular compiler, the
heap is not the same as free store and memory
allocated in one area cannot be safely
deallocated in the other. Memory allocated from
the heap can be used for objects of class type
by placement-new construction and explicit
destruction. If so used, the notes about free
store object lifetime apply similarly here.
Global/Static Global or static variables and objects have
their storage allocated at program startup, but
may not be initialized until after the program
has begun executing. For instance, a static
variable in a function is initialized only the
first time program execution passes through its
definition. The order of initialization of
global variables across translation units is not
defined, and special care is needed to manage
dependencies between global objects (including
class statics). As always, uninitialized proto-
objects' storage may be accessed and manipulated
through a void* but no nonstatic members or
member functions may be used or referenced
outside the object's actual lifetime.
Note about Heap vs. Free Store: We distinguish between "heap" and "free store" because the draft deliberately leaves unspecified the question of whether these two areas are related. For example, when memory is deallocated via operator delete, 18.4.1.1 states:
It is unspecified under what conditions part or all of such reclaimed storage is allocated by a subsequent call to operator new or any of calloc, malloc, or realloc, declared in
Similarly, it is unspecified whether new/delete is implemented in terms of malloc/free or vice versa in a given implementation. Effectively, the two areas behave differently and are accessed differently -- so be sure to use them differently!