mtmalloc(3MALLOC)                                                                                                                mtmalloc(3MALLOC)

NAME

       mtmalloc, mallocctl - MT hot memory allocator

SYNOPSIS

       #include <mtmalloc.h>
       cc -o a.out -lthread -lmtmalloc

       void *malloc(size_t size);

       void free(void *ptr);

       void *memalign(size_t alignment, size_t size);

       void *realloc(void *ptr, size_t size);

       void *valloc(size_t size);

       void mallocctl(int cmd, long value);

       The  malloc()  and free() functions provide a simple general-purpose memory allocation package that is suitable for use in high performance
       multithreaded applications. The suggested use of this library is in multithreaded applications;  it can be used for single threaded  appli-
       cations,  but  there  is  no  advantage in doing so. This library cannot be dynamically loaded with dlopen(3C) during runtime because there
       must be only one manager of the process heap.

       The malloc() function returns a pointer to a block of at least size bytes suitably aligned for any use.

       The argument to free() is a pointer to a block previously allocated by malloc() or realloc(). After  free()  is  performed  this  space  is
       available for further allocation. If  ptr is a null pointer, no action occurs. The free() function does not set errno.

       Undefined  results  will occur if the space assigned by malloc() is overrun or if a random number is handed to free(). A freed pointer that
       is passed to free() will send a  SIGABRT signal to the calling process. This behavior is controlled by mallocctl().

       The memalign() function allocates size bytes on a specified alignment boundary and returns a pointer to the allocated block. The  value  of
       the  returned  address is guaranteed to be an even multiple of alignment. Note that the value of alignment must be a power of two, and must
       be greater than or equal to the size of a word.

       The realloc() function changes the size of the block pointed to by ptr to size bytes and returns a pointer to the (possibly  moved)  block.
       The  contents will be unchanged up to the lesser of the new and old sizes. If the new size of the block requires movement of the block, the
       space for the previous instantiation of the block is freed. If the new size is larger, the contents of the newly allocated portion  of  the
       block  are unspecified. If ptr is NULL, realloc() behaves like malloc() for the specified size. If size is 0 and ptr is not a null pointer,
       the space pointed to is freed.

       The valloc() function has the same effect as malloc(), except that the allocated memory will be aligned to a multiple of the value returned
       by sysconf(_SC_PAGESIZE).

       After possible pointer coercion, each allocation routine returns  a pointer to a space that is suitably aligned  for storage of any type of
       object.

       The malloc(), realloc(), memalign(), and valloc() functions will fail if there is not enough available memory.

       The mallocctl() function controls the behavior of the malloc library. The options fall into two general classes, debugging options and per-
       formance options.

       MTDOUBLEFREE            Allows  double   free  of  a pointer.   Setting value to 1 means yes and 0 means no. The default behavior of double
                               free results in a core dump.

       MTDEBUGPATTERN          Writes misaligned data into the buffer after free(). When the buffer is reallocated, the contents are  verified  to
                               ensure  that there was no access to the buffer after the free. If the buffer has been dirtied, a  SIGABRT signal is
                               delivered to the process. Setting  value to 1 means yes and 0 means no. The default behavior is to  not write  mis-
                               aligned data.  The pattern used  is 0xdeadbeef. Use of this option results in a performance penalty.

       MTINITBUFFER            Writes  misaligned  data  into the newly allocated buffer. This option is useful for detecting some accesses before
                               initialization. Setting value to 1 means yes and 0 means no. The default behavior is to not write  misaligned  data
                               to the newly allocated buffer. The pattern used is 0xbaddcafe. Use of this option results in a performance penalty.

       MTCHUNKSIZE             This  option  changes  the  size  of allocated memory when a pool has exhausted all available memory in the buffer.
                               Increasing this  value allocates more memory for the  application.   A  substantial   performance  gain  can  occur
                               because  the  library makes fewer calls  to the OS for more memory. Acceptable number values are between 9 and 256.
                               The default value is  9. This value is multiplied by 8192.

       If there is no available memory, malloc(), realloc(), memalign(), and valloc() return a null pointer. When realloc() is called with size  >
       0  and  returns NULL, the block pointed to by ptr is left intact. If size, nelem, or elsize is 0, either a null pointer or a unique pointer
       that can be passed to free() is returned.

       If malloc() or realloc() returns unsuccessfully, errno will be set to indicate the error.

       The malloc() and realloc() functions will fail if:

       ENOMEM          The physical limits of the system are exceeded by size bytes of memory which cannot be allocated.

       EAGAIN          There is not enough memory available to allocate size bytes of memory; but the application could try again later.

       Comparative features of the various allocation libraries can be found in the umem_alloc(3MALLOC) manual page.

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE         |      ATTRIBUTE VALUE        |
       +-----------------------------+-----------------------------+
       |MT-Level                     |Safe                         |
       +-----------------------------+-----------------------------+

       brk(2), getrlimit(2), bsdmalloc(3MALLOC), dlopen(3C), malloc(3C), malloc(3MALLOC),  mapmalloc(3MALLOC),  signal.h(3HEAD),  umem_alloc(3MAL-
       LOC), watchmalloc(3MALLOC), attributes(5)

WARNINGS

       Undefined results will occur if the size requested for a block of memory exceeds the maximum size of a process's heap. This information may
       be obtained using  getrlimit().

                                                                    21 Mar 2005                                                  mtmalloc(3MALLOC)