BIO_new.3ossl - Man Page

BIO allocation and freeing functions


 #include <openssl/bio.h>

 BIO *BIO_new_ex(OSSL_LIB_CTX *libctx, const BIO_METHOD *type);
 BIO *BIO_new(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_ex() function returns a new BIO using method type associated with the library context libctx (see OSSL_LIB_CTX(3)). The library context may be NULL to indicate the default library context.

The BIO_new() is the same as BIO_new_ex() except the default library context is always used.

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_ex() and BIO_new() return a newly created BIO or NULL if the call fails.

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.

BIO_new_ex() was added in OpenSSL 3.0.


Create a memory BIO:

 BIO *mem = BIO_new(BIO_s_mem());

Referenced By

bio.7ossl(7), BIO_meth_new.3ossl(3), BIO_s_dgram_pair.3ossl(3), COMP_CTX_new.3ossl(3), ossl-guide-migration.7ossl(7), ossl-guide-quic-client-block.7ossl(7), ossl-guide-tls-client-block.7ossl(7).

The man pages BIO_free.3ossl(3), BIO_free_all.3ossl(3), BIO_new_ex.3ossl(3), BIO_up_ref.3ossl(3) and BIO_vfree.3ossl(3) are aliases of BIO_new.3ossl(3).

2024-02-09 3.2.1 OpenSSL