migration_guide: Mention ERR_GET_FUNC() and function code removal

Fixes #16817

Reviewed-by: Dmitry Belyavskiy <beldmit@gmail.com>
Reviewed-by: Paul Dale <pauli@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/16879)

diff --git a/doc/man7/migration_guide.pod b/doc/man7/migration_guide.pod
index 3e4ce9f65a6def145e649ea076735116a37a29b5..627173f180b0af84787c49852bd1326163312234 100644 (file)
--- a/doc/man7/migration_guide.pod
+++ b/doc/man7/migration_guide.pod
@@ -451,6 +451,11 @@ For example when setting an unsupported curve with
 EVP_PKEY_CTX_set_ec_paramgen_curve_nid() this function call will not fail
 but later keygen operations with the EVP_PKEY_CTX will fail.
 
+=head4 Removal of function code from the error codes
+
+The function code part of the error code is now always set to 0. For that
+reason the ERR_GET_FUNC() macro was removed. Applications must resolve
+the error codes only using the library number and the reason code.
 
 =head2 Installation and Compilation