BIO_new.3ssl man page

BIO_new, BIO_up_ref, BIO_free, BIO_vfree, BIO_free_all, BIO_set — BIO allocation and freeing functions


#include <openssl/bio.h>
BIO *  BIO_new(const BIO_METHOD *type);
int    BIO_set(BIO *a, const BIO_METHOD *type);
int    BIO_up_ref(BIO *a);
int    BIO_free(BIO *a);
void   BIO_vfree(BIO *a);
void   BIO_free_all(BIO *a);


The BIO_new() function returns a new BIO using method type.

BIO_up_ref() increments the reference count associated with the BIO object.

BIO_free() frees up a single BIO, BIO_vfree() also frees up a single BIO but it does not return a value. If a is NULL nothing is done. Calling BIO_free() may also have some effect on the underlying I/O structure, for example it may close the file being referred to under certain circumstances. For more details see the individual BIO_METHOD descriptions.

BIO_free_all() frees up an entire BIO chain, it does not halt if an error occurs freeing up an individual BIO in the chain. If a is NULL nothing is done.

Return Values

BIO_new() returns a newly created BIO or NULL if the call fails.

BIO_set(), BIO_up_ref() and BIO_free() return 1 for success and 0 for failure.

BIO_free_all() and BIO_vfree() do not return values.


If BIO_free() is called on a BIO chain it will only free one BIO resulting in a memory leak.

Calling BIO_free_all() on a single BIO has the same effect as calling BIO_free() on it other than the discarded return value.


BIO_set() was removed in OpenSSL 1.1.0 as BIO type is now opaque.


Create a memory BIO:

BIO *mem = BIO_new(BIO_s_mem());