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The Question is:
A philosophical question. Malloc() allocates memory on the heap. But there is
as far as I know no equivalent function to allocate memory on the stack as for
example for array abc in
func()
char abc[SIZE];
...
when SIZE is not known until run-time.
Why not? The advantage would be automatic deallocation upon function return
thereby eliminating the need to manually deallocate and the risk of forgetting
to free the memory.
Thank you very much.
The Answer is :
You will want to direct your question to the C standards body, as
there is no C standards compliant mechanism for this. C++ attempts
to address some of the omissions in the C model, and particularly
in this case with the C++ concepts of constructors and destructors
and such.
Some C compiler implementations do provide an alloca() mechanism,
Compaq C has the __ALLOCA built-in function and the asm directive
(direct manipulation of the stack pointer) for those programmers
wishing to create platform-specific coding.
As is the case with stack-based memory allocations such as
function-local variables, you must exercise care with alloca-based
memory allocations. Should references to the stack-based memory
area "outlive" the validity of the stack frame itself, various
corruptions can ensue.
C memory management itself is inherently rather generic in nature,
and thus can be ill-suited for certain applications. (The RTL VM
services underlying the C malloc() and free() calls do attempt to
learn the application memory access patterns.)
If you wish to manage your own memory, you can also use VM zones
for this purpose, and take full control over the lookaside list
sizes and other attributes. Further, you can designate (within
your application) one VM zone as a temporary memory zone, and flush
the entire zone when, for instance, the program is ready to prompt
for a new user command; when all temporary memory utilized by the
last command processed can be safely freed.
Also please see topic (6811).
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