doc/crypto/OPENSSL_malloc.pod

=pod

=head1 NAME

OPENSSL_malloc_init,
OPENSSL_malloc, OPENSSL_zalloc, OPENSSL_realloc, OPENSSL_free,
OPENSSL_clear_realloc, OPENSSL_clear_free,
CRYPTO_malloc, CRYPTO_zalloc, CRYPTO_realloc, CRYPTO_free,
OPENSSL_strdup, OPENSSL_strndup,
OPENSSL_memdup, OPENSSL_strlcpy, OPENSSL_strlcat,
CRYPTO_clear_realloc, CRYPTO_clear_free,
CRYPTO_get_mem_functions, CRYPTO_set_mem_functions,
CRYPTO_set_mem_debug, CRYPTO_mem_ctrl,
OPENSSL_mem_debug_push, OPENSSL_mem_debug_pop,
CRYPTO_mem_debug_push, CRYPTO_mem_debug_pop,
CRYPTO_mem_leaks, CRYPTO_mem_leaks_fp - Memory allocation functions

=head1 SYNOPSIS

 #include <openssl/crypto.h>

 int OPENSSL_malloc_init(void)

 void *OPENSSL_malloc(size_t num)
 void *OPENSSL_zalloc(size_t num)
 void *OPENSSL_realloc(void *addr, size_t num)
 void OPENSSL_free(void *addr)
 char *OPENSSL_strdup(const char *str)
 char *OPENSSL_strndup(const char *str, size_t s)
 void *OPENSSL_clear_realloc(void *p, size_t old_len, size_t num)
 void OPENSSL_clear_free(void *str, size_t num)
 void OPENSSL_cleanse(void *ptr, size_t len);

 void *CRYPTO_malloc(size_t num, const char *file, int line)
 void *CRYPTO_zalloc(size_t num, const char *file, int line)
 void *CRYPTO_realloc(void *p, size_t num, const char *file, int line)
 void CRYPTO_free(void *str)
 char *CRYPTO_strdup(const char *p, const char *file, int line)
 char *CRYPTO_strndup(const char *p, size_t num, const char *file, int line)
 void *CRYPTO_clear_realloc(void *p, size_t old_len, size_t num, const char *file, int line)
 void CRYPTO_clear_free(void *str, size_t num)

 void CRYPTO_get_mem_functions(
         void *(**m)(size_t, const char *, int),
         void *(**r)(void *, size_t, const char *, int),
         void (**f)(void *))
 int CRYPTO_set_mem_functions(
         void *(*m)(size_t, const char *, int),
         void *(*r)(void *, size_t, const char *, int),
         void (*f)(void *))

 int CRYPTO_set_mem_debug(int onoff)

 #define CRYPTO_MEM_CHECK_OFF
 #define CRYPTO_MEM_CHECK_ON
 #define CRYPTO_MEM_CHECK_DISABLE
 #define CRYPTO_MEM_CHECK_ENABLE

 int CRYPTO_mem_ctrl(int flags);

 int OPENSSL_mem_debug_push(const char *info)
 int OPENSLS_mem_debug_pop)(void)

 int CRYPTO_mem_debug_push(const char *info, const char *file, int line);

 void CRYPTO_mem_leaks(BIO *b);
 void CRYPTO_mem_leaks(FILE *fp);

=head1 DESCRIPTION

OpenSSL memory allocation is handled by the B<OPENSSL_xxx> API. These are
generally macro's that add the standard C B<__FILE__> and B<__LINE__>
parameters and call a lower-level B<CRYPTO_xxx> API.
Some functions do not add those parameters, but exist for consistency.

OPENSSL_malloc_init() sets the lower-level memory allocation functions
to their default implementation.
It is generally not necessary to call this, except perhaps in certain
shared-library situations.

OPENSSL_malloc(), OPENSSL_realloc(), and OPENSSL_free() are like the
C malloc(), realloc(), and free() functions.
OPENSSL_zalloc() calls memset() to zero the memory before returning.

OPENSSL_clear_realloc() and OPENSSL_clear_free() should be used
when the buffer at B<addr> holds sensitive information.
The old buffer is filled with arbitrary data by calling OPENSSL_cleanse()
before ultimately calling OPENSSL_free().

OPENSSL_strdup(), OPENSSL_strndup() and OPENSSL_memdup() are like the
equivalent C functions, except that memory is allocated by calling the
OPENSSL_malloc() and should be releaed by calling OPENSSL_free().

OPENSSL_strlcpy(),
OPENSSL_strlcat() and OPENSSL_strnlen() are equivalents of the common C
library functions and are provided for portability.

If no allocations have been done, it is possible to "swap out" the default
implementations and replace them with alternate versions, or wrappers that
do some additional housekeeping and then defer to the OpenSSL implementation.
The CRYPTO_get_mem_functions() function fills in the function pointers for
with the current functions (normally, and by default,
CRYPTO_malloc(), CRYPTO_realloc(), and CRYPTO_free()).
The CRYPTO_set_mem_functions() specifies a different set of functions.
If any of B<m>, B<r>, or B<f> are NULL, then the function is not changed.

The default implementation can include some debugging capability (if enabled
at build-time).
This adds some overhead by keeping a list of all memory allocations, and
removes items from the list when they are free'd.
This is most useful for identifying memory leaks.
CRYPTO_set_mem_debug() turns this tracking on and off.  It is normally
called at startup, but can be called at any time.

Finer-grain control of the tracking can be done with CRYPTO_mem_ctrl().
The most common case is to enable tracking, which is done by using
the B<CRYPTO_MEM_CHECK_ON> constant; it can be turned off by using
the B<CRYPTO_MEM_CHECK_OFF> value.  The disable and enable values are
most commonly used within OpenSSL to termporarily suspend and restore
tracking of library internals.

While checking memory, it can be useful to store additional context
about what is being done.
For example, identifying the field names when parsing a complicated
data structure.
OPENSSL_mem_debug_push() (which calls CRYPTO_mem_debug_push())
attachs an identifying string to the allocation stack.
This must be a global or other static string; it is not copied.
OPENSSL_mem_debug_pop() removes identifying state from the stack.

At the end of the program, calling CRYPTO_mem_leaks() or
CRYPTO_mem_leaks_fp() will
report all "leaked" memory, writing it to the specified BIO B<b>
or FILE B<fp>.
Depending on how OpenSSL is built, it may then abort if there
are any unfree'd allocations, for debugging.

=head1 RETURN VALUES

OPENSSL_malloc_init(), OPENSSL_free(), OPENSSL_clear_free()
CRYPTO_free(), CRYPTO_clear_free(),
CRYPTO_get_mem_functions(), and
CRYPTO_mem_leaks()
return no value.

OPENSSL_malloc(), OPENSSL_zalloc(), OPENSSL_realloc(),
OPENSSL_clear_realloc(),
CRYPTO_malloc(), CRYPTO_zalloc(), CRYPTO_realloc(),
CRYPTO_clear_realloc(),
OPENSSL_strdup(), and OPENSSL_strndup()
return a pointer to allocated memory or NULL on error.

CRYPTO_set_mem_functions() and CRYPTO_set_mem_debug()
return 1 on success or 0 on failure (almost
always because allocations have already happened).

CRYPTO_mem_ctrl() return the previous value of the flag.

OPENSSL_mem_debug_push() and OPENSSL_mem_debug_pop()
return 1 on success or 0 on failure.

=cut