Memory management¶
Memory allocation functions¶
The file flint.h
defines functions flint_malloc
,
flint_realloc
, flint_calloc
and flint_free
.
They have the same interface as the standard library functions, but
may perform additional error checking.
By default the memory allocation functions wrap the system’s
malloc
, realloc
, calloc
and free
.
The user can override this behaviour by calling __flint_set_memory_functions
passing the malloc
, realloc
, calloc
and free
function
pointers as parameters (see flint.h
for the exact prototype).
The current memory functions can be returned in a similar manner by calling
__flint_get_memory_functions
passing the address of pointers in which
the function pointers can be stored.
Memory allocated with flint_malloc
must be freed with
flint_free
and not with free
.
Global caches and cleanup¶
FLINT may cache some data (such as allocated integers and tables of prime numbers) to speed up various computations. If FLINT is built in threadsafe mode, most caches are thread-local (some are always global and shared among the threads).
Data cached by the current thread can be freed by calling the
flint_cleanup()
function. The user can register additional cleanup
functions to be invoked
by flint_cleanup()
by passing a pointer
to a function with signature void cleanup_function(void)
to flint_register_cleanup_function()
.
The user should call flint_cleanup_master()
exactly once
right before exiting a program. This cleans up all caches in all threads
and should result in a clean output with tools like valgrind
if there are no memory leaks.
Temporary allocation¶
FLINT allows for temporary allocation of memory using alloca
to allocate on the stack if the allocation is small enough.
The following program demonstrates how to use this facility to allocate two different arrays.
#include <gmp.h>
#include "flint.h"
void myfun(void)
{
/* other variable declarations */
nn_ptr a, b;
TMP_INIT;
/* arbitrary code */
TMP_START; /* we are about to do some allocation */
/* arbitrary code */
a = TMP_ALLOC(32*sizeof(ulong));
b = TMP_ALLOC(64*sizeof(ulong));
/* arbitrary code */
TMP_END; /* cleans up a and b */
/* arbitrary code */
}
It is very important to note that temporary allocations should not be made in recursive functions or in loop bodies, as many small allocations on the stack can exhaust the stack causing a stack overflow.