Debugging Memory Heaps
Memory Management Functions
Managing Memory with Multiple Memory Heaps
Format
#include <umalloc.h>
void *_debug_ucalloc(Heap_t heap, size_t num, size_t size,
const char *file, size_t line);
Language Level: Extension
_debug_ucalloc is the debug version of _ucalloc. Like _ucalloc, it allocates memory from the heap you specify for an array of num elements, each of length size bytes. It then initializes all bits of each element to 0.
In addition, _debug_ucalloc makes an implicit call to _uheap_check, and stores the name of the file file and the line number line where the storage is allocated. This information can be used later by the _uheap_check, _uheap_allocated, or _udump_allocated_delta functions.
To use _debug_ucalloc, you must compile with the debug memory -qheapdebug compiler option. This option maps all _ucalloc calls to _debug_ucalloc.
Note: The -qheapdebug option maps all calls to memory management functions (including heap-specific versions) to their debug counterparts. To prevent a call from being mapped, parenthesize the function name.
_debug_ucalloc works just like _debug_calloc except that you specify the heap to use; _debug_calloc always allocates from the default heap.
If the heap does not have enough memory for the request, _debug_ucalloc calls the getmore_fn that you specified when you created the heap with _ucreate.
To reallocate or free memory allocated with _debug_ucalloc, use the non-heap-specific _debug_realloc and _debug_free. These functions always check what heap the memory was allocated from.
Return Value
_debug_ucalloc returns a pointer to the reserved space.
If size or num was
specified as zero, or if your getmore_fn cannot provide
enough memory, _debug_ucalloc returns NULL.
Passing _debug_ucalloc a heap that is not valid
results in undefined behavior.
Example
This example creates a user heap and allocates memory from it
with _debug_ucalloc. It then attempts to write
to memory that was not allocated. When _debug_free
is called, _uheap_check detects the error,
generates several messages, and stops the program.
Note: You must compile this example with the -qheapdebug option to map the _ucalloc calls to _debug_ucalloc and free to _debug_free.
#include <stdlib.h> #include <stdio.h> #include <umalloc.h> #include <string.h>
int main(void)
{
Heap_t myheap;
char *ptr;
/* Use default heap as user heap */ myheap = _udefault(NULL);
if (NULL == (ptr = (char*)_ucalloc(myheap, 100, 1))) {
puts("Cannot allocate memory from user heap.");
exit(EXIT_FAILURE);
}
memset(ptr, 'x', 105); /* Overwrites storage that was not allocated */
free(ptr);
return 0;
/****************************************************************************
The output should be similar to :
End of allocated object 0x00073890 was overwritten at 0x000738f4.
The first eight bytes of the memory block (in hex) are: 7878787878787878.
This memory block was (re)allocated at line number 14 in _debug_ucallo.c.
Heap state was valid at line 14 of _debug_ucallo.c.
Memory error detected at line 19 of _debug_ucallo.c.
****************************************************************************/
}
Debugging Memory Heaps
Memory Management Functions
Managing Memory with Multiple
Memory Heaps
Debugging Problems with Heap
Memory
-qheapdebug Compiler
Option
_debug_calloc - Allocate and Initialize
Memory
_debug_free - Free Allocated Memory
_debug_heapmin - Free Unused Memory in the
Default Heap
_debug_malloc - Allocate Memory
_debug_memcpy - Copy Bytes
_debug_memmove - Copy Bytes
_debug_memset - Set Bytes to Value
_debug_realloc - Reallocate Memory Block
_debug_strcat - Concatenate Strings
_debug_strcpy - Copy Strings
_debug_strncat - Concatenate Strings
_debug_strncpy - Copy Strings
_debug_strnset - Set Characters in String
_debug_strset - Set Characters in String
_debug_uheapmin - Free Unused Memory in
User Heap
_debug_umalloc - Reserve Memory Block from
User Heap
