[Bug 1472] malloc_boundary.c:89: warning: left shift count >= width of type

[bugzilla-daemon at rtems.org]

https://www.rtems.org/bugzilla/show_bug.cgi?id=1472

--- Comment #5 from Sebastian Huber <sebastian.huber at embedded-brains.de> 2010-06-25 02:31:27 CDT ---
(In reply to comment #4)
> (In reply to comment #3)
> > I have a debug support for the super core heap handler.  It covers boundary
> > violations, general heap block corruption, double free and usage of freed
> > memory.  The space overhead is 4 words per heap block.  The time overhead is
> > minimal for allocations and during free it depends on the allocation size (the
> > freed memory will be marked with a pattern).
> 
> Nice. Is this plugable ? It would be nice to take a known working RTEMS and
> turn this on when needed by an application.

It is plugable:

  typedef struct {
    void *handler_data;
    void (*init_block)(Heap_Control *heap, Heap_Block *block);
    bool (*check_block)(Heap_Control *heap, Heap_Block *block);
    void (*block_error)(Heap_Control *heap, Heap_Block *block);
    Heap_Block *first_delayed_free_block;
    Heap_Block *last_delayed_free_block;
    uintptr_t delayed_free_block_count;
  } Heap_Protection;

If enable, this structure is a part of Heap_Control.  The handler functions
will be called by the general heap code.

In order to check if a heap block (Heap_Block) is valid I added protector
fields (the previous value of a 4 word overhead was incorrect, we have 6
words):

  typedef struct {
    uintptr_t protector [HEAP_PROTECTOR_COUNT];
    Heap_Block *next_delayed_free_block;
    Thread_Control *task;
  } Heap_Block_protection_begin;

  typedef struct {
    uintptr_t protector [HEAP_PROTECTOR_COUNT];
  } Heap_Block_protection_end;


struct Heap_Block {
  uintptr_t prev_size;

  #ifdef HEAP_PROTECTION
    Heap_Block_protection_begin Protection_begin;
  #endif

  uintptr_t size_and_flag;

  #ifdef HEAP_PROTECTION
    Heap_Block_protection_end Protection_end;
  #endif

  Heap_Block *next;
  Heap_Block *prev;
};

They will catch a boundary violation with a high probability.  Here we have a
space overhead which may be to much for certain applications, thus I would not
enable this feature by default.

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