wnmemd(3)

NAME

wn_print_all_groups_mem_used, wn_mem_in_group,

wn_print_gp_stack, wn_gplabel, wn_gp_fill, wn_gp_pad,

wn_stack_fill, wn_gp_trap_address, wn_allmem_verify,

wn_group_verify, wn_mem_used, wn_group_mem_used,

wn_print_mem_used, wn_print_group_mem_used - debugging aids for

applications using wnmem

SYNOPSIS

#include <wn/wnlib.h>
wn_gp_fill()
wn_gp_pad()
wn_stack_fill()
wn_gp_trap_address(address)
ptr address;
wn_allmem_verify()
wn_group_verify(group)
wn_memgp group;
int wn_mem_used()
int wn_group_mem_used(group)
wn_memgp group;
wn_print_mem_used()
wn_print_group_mem_used(group)
wn_memgp group;
wn_print_all_groups_mem_used()
bool wn_mem_in_group(p,group)
ptr p;
wn_memgp group;
wn_print_gp_stack()
wn_gplabel(label)
char label[];

DESCRIPTION

These routines aid in debugging applications that use wn

mem. In particular, these routines help detect the following

problems:

1) use of uninitialized allocated memory

2) use of memory that has already been freed

3) array overflows and wild stores

4) leakage of memory. Memory is lost but not freed.

wn_gp_fill helps detect problems 1 and 2 above. It should

be called before any of the wnmem calls. If wn_gp_fill has been

called, wn_alloc fills memory it returns with 'a' characters, en

suring that this memory is not NULL. Application code that is

relying on this memory to be NULL will probably crash immediately

and reliably. Further, wn_gp_free and wn_free fill memory they

free with 'f' characters; application code that continues to rely

on this memory will probably crash immediately and reliably.

wn_gp_pad helps detect problem 3 above. It should be

called before any of the wnmem calls. If wn_gp_pad has been

called, wn_alloc and wn_zalloc allocate an extra block of memory

called a pad, in addition to the requested memory. The pad memo

ry is initialized to a known value. Because the pad is contigu

ous with the requested memory, it will probably be overwritten in

the event of an array overflow or a wild store. wn_allmem_verify

checks if any of the pads are changed; if so it crashes with a

message. Use wn_allmem_verify to binary search the application

for the problem.

wn_allmem_verify checks the memory allocator for inconsis

tancies. If wn_gp_pad has been called, it helps detect array

overflows and wild stores.

wn_group_verify verifies an individual memory group.

wn_print_mem_used prints the total amount of memory allo

cated but not freed, which is helpful for detecting memory leaks.

wn_print_group_mem_used prints the total amount of memory

allocated but not freed in the memory group, which is helpful for

detecting memory leaks.

wn_print_all_groups_mem_used prints the total amount of

memory allocated but not freed in each memory group separately,

then prints a total for all groups.

wn_mem_in_group returns TRUE iff pointer p was allocated

from memory group group.

wn_print_gp_stack prints the memory group stack.

wn_gplabel assigns a char string label to the current

group for debugging purposes. Other routines use this label if

it is available. Use wn_gplabel immediately after wn_gpmake(3).

wn_gp_trap_address causes allocations of memory at address

to crash. Useful for finding where a pointer is allocated.

SEE ALSO

wnmem, wnmlc man/papers/heisen.bug

AUTHOR

Will Naylor

WNLIB August 23, 1998

WNMEMD(3)