ERR_print_errors() is a convenience function that prints the error
strings for all errors that OpenSSL has recorded to bp, thus emptying the error queue.
ERR_print_errors_fp() is the same, except that the output goes to a
FILE.
The error strings will have the following format:
[pid]:error:[error code]:[library name]:[function name]:[reason string]:[file name]:[line]:[optional text message]
error code is an 8 digit
hexadecimal number. library name,
function name and reason string are ASCII text, as is
optional text message if one was
set for the respective error code.
If there is no text string registered for the given error code, the
error string will contain the numeric code.
RETURN VALUES
ERR_print_errors() and ERR_print_errors_fp() return no values.