HP C/iX Library Reference Manual (30026-90004)

Chapter 5 245
HP C/iX Library Function Descriptions
mallopt
mallopt
Provides control over the memory allocation algorithm.
Syntax
#include <malloc.h>
int mallopt (int cmd , int value );
Parameters
cmd The available values for cmd are:
M_MXFAST Set maxfast to
value . The algorithm allocates all blocks
below the size of maxfast in large groups and then passes
them out very quickly. The default value for maxfast is 24.
M_NLBLKS Set numlblks to
value . The above mentioned large groups
each contain numlblks blocks. Numlblks must be greater
than 1. The default value for numlblks is 100.
M_GRAIN Set grain to
value . The sizes of all blocks smaller than
maxfast are considered to be rounded up to the nearest
multiple of grain. grain must be greater than zero. The
default value of grain is the smallest number ofbytes that
allows alignment of any data type. The
value parameter is
rounded up to a multiple of the default when grain is set.
M_KEEP Preserve data in a freed block until the next malloc,
realloc, or calloc. This option is provided only for
compatibility with other systems and is not recommended.
value An integer value used by cmd .
Return Values
0 Success.
1 Indicates malloc() has been previously called or that arguments have
illegal values.
Description
The mallopt function returns a pointer to space suitably aligned, after possible pointer
coercion, for storage of any type of object. It also provides control over the main memory
allocation algorithm. The mallopt function may be called repeatedly, but may not be called
after the first small block is allocated.
The contents of a block are not preserved when it is freed, unless the M_KEEP option of
mallopt() is specified in
cmd .