Hi all, According to the manpage at https://www.openssl.org/docs/man1.1.0/man3/BIO_s_file.html the macro BIO_tell() casts to int: /opt/local/include//openssl/bio.h:# define BIO_tell(b) (int)BIO_ctrl(b,BIO_C_FILE_TELL,0,NULL) What happens if the file being parsed is larger than can fit in an int? Does BIO_s_file() do anything to limit the size of the file? Does openssl detect overflow, or do I have to detect overflow? Regards, Graham —