
 OPENSSL INSTALLATION
 --------------------

 [This document describes installation on all supported operating
  systems (currently mainly the Linux/Unix family, OpenVMS and
  Windows)]

 To install OpenSSL, you will need:

  * A make implementation
  * Perl 5 with core modules (please read NOTES.PERL)
  * The perl module Text::Template (please read NOTES.PERL)
  * an ANSI C compiler
  * a development environment in the form of development libraries and C
    header files
  * a supported operating system

 For additional platform specific requirements and other details,
 please read one of these:

  * NOTES.VMS (OpenVMS)
  * NOTES.WIN (any supported Windows)
  * NOTES.DJGPP (DOS platform with DJGPP)

 Quick Start
 -----------

 If you want to just get on with it, do:

  on Unix:

    $ ./config
    $ make
    $ make test
    $ make install

  on OpenVMS:

    $ @config
    $ mms
    $ mms test
    $ mms install

  on Windows (only pick one of the targets for configuration):

    $ perl Configure { VC-WIN32 | VC-WIN64A | VC-WIN64I | VC-CE }
    $ nmake
    $ nmake test
    $ nmake install

 [If any of these steps fails, see section Installation in Detail below.]

 This will build and install OpenSSL in the default location, which is:

  Unix:    normal installation directories under /usr/local
  OpenVMS: SYS$COMMON:[OPENSSL-'version'...], where 'version' is the
           OpenSSL version number with underscores instead of periods.
  Windows: C:\Program Files\OpenSSL or C:\Program Files (x86)\OpenSSL

 If you want to install it anywhere else, run config like this:

  On Unix:

    $ ./config --prefix=/opt/openssl --openssldir=/usr/local/ssl

  On OpenVMS:

    $ @config --prefix=PROGRAM:[INSTALLS] --openssldir=SYS$MANAGER:[OPENSSL]


 Configuration Options
 ---------------------

 There are several options to ./config (or ./Configure) to customize
 the build (note that for Windows, the defaults for --prefix and
 --openssldir depend in what configuration is used and what Windows
 implementation OpenSSL is built on.  More notes on this in NOTES.WIN):

  --api=x.y.z
                   Don't build with support for deprecated APIs below the
                   specified version number. For example "--api=1.1.0" will
                   remove support for all APIS that were deprecated in OpenSSL
                   version 1.1.0 or below.

  --cross-compile-prefix=PREFIX
                   The PREFIX to include in front of commands for your
                   toolchain. It's likely to have to end with dash, e.g.
                   a-b-c- would invoke GNU compiler as a-b-c-gcc, etc.
                   Unfortunately cross-compiling is too case-specific to
                   put together one-size-fits-all instructions. You might
                   have to pass more flags or set up environment variables
                   to actually make it work. Android and iOS cases are
                   discussed in corresponding Configurations/10-main.cf
                   sections. But there are cases when this option alone is
                   sufficient. For example to build the mingw64 target on
                   Linux "--cross-compile-prefix=x86_64-w64-mingw32-"
                   works. Naturally provided that mingw packages are
                   installed. Today Debian and Ubuntu users have option to
                   install a number of prepackaged cross-compilers along
                   with corresponding run-time and development packages for
                   "alien" hardware. To give another example
                   "--cross-compile-prefix=mipsel-linux-gnu-" suffices
                   in such case. Needless to mention that you have to
                   invoke ./Configure, not ./config, and pass your target
                   name explicitly.

  --debug
                   Build OpenSSL with debugging symbols.

  --libdir=DIR
                   The name of the directory under the top of the installation
                   directory tree (see the --prefix option) where libraries will
                   be installed. By default this is "lib". Note that on Windows
                   only ".lib" files will be stored in this location. dll files
                   will always be installed to the "bin" directory.

  --openssldir=DIR
                   Directory for OpenSSL configuration files, and also the
                   default certificate and key store.  Defaults are:

                   Unix:           /usr/local/ssl
                   Windows:        C:\Program Files\Common Files\SSL
                                or C:\Program Files (x86)\Common Files\SSL
                   OpenVMS:        SYS$COMMON:[OPENSSL-COMMON]

  --prefix=DIR
                   The top of the installation directory tree.  Defaults are:

                   Unix:           /usr/local
                   Windows:        C:\Program Files\OpenSSL
                                or C:\Program Files (x86)\OpenSSL
                   OpenVMS:        SYS$COMMON:[OPENSSL-'version']

  --release
                   Build OpenSSL without debugging symbols. This is the default.

  --strict-warnings
                   This is a developer flag that switches on various compiler
                   options recommended for OpenSSL development. It only works
                   when using gcc or clang as the compiler. If you are
                   developing a patch for OpenSSL then it is recommended that
                   you use this option where possible.

  --with-zlib-include=DIR
                   The directory for the location of the zlib include file. This
                   option is only necessary if enable-zlib (see below) is used
                   and the include file is not already on the system include
                   path.

  --with-zlib-lib=LIB
                   On Unix: this is the directory containing the zlib library.
                   If not provided the system library path will be used.
                   On Windows: this is the filename of the zlib library (with or
                   without a path). This flag must be provided if the
                   zlib-dynamic option is not also used. If zlib-dynamic is used
                   then this flag is optional and a default value ("ZLIB1") is
                   used if not provided. 
                   On VMS: this is the filename of the zlib library (with or
                   without a path). This flag is optional and if not provided
                   then "GNV$LIBZSHR", "GNV$LIBZSHR32" or "GNV$LIBZSHR64" is
                   used by default depending on the pointer size chosen.

  no-afalgeng
                   Don't build the AFALG engine. This option will be forced if
                   on a platform that does not support AFALG.

  enable-asan
                   Build with the Address sanitiser. This is a developer option
                   only. It may not work on all platforms and should never be
                   used in production environments. It will only work when used
                   with gcc or clang and should be used in conjunction with the
                   no-shared option.

  no-asm
                   Do not use assembler code. On some platforms a small amount
                   of assembler code may still be used.

  no-async
                   Do not build support for async operations.

  no-autoalginit
                   Don't automatically load all supported ciphers and digests.
                   Typically OpenSSL will make available all of its supported
                   ciphers and digests. For a statically linked application this
                   may be undesirable if small executable size is an objective.
                   This only affects libcrypto. Ciphers and digests will have to
                   be loaded manually using EVP_add_cipher() and
                   EVP_add_digest() if this option is used. This option will
                   force a non-shared build.

  no-autoerrinit
                   Don't automatically load all libcrypto/libssl error strings.
                   Typically OpenSSL will automatically load human readable
                   error strings. For a statically linked application this may
                   be undesirable if small executable size is an objective.


  no-capieng
                   Don't build the CAPI engine. This option will be forced if
                   on a platform that does not support CAPI.

  no-cms
                   Don't build support for CMS features

  no-comp
                   Don't build support for SSL/TLS compression. If this option
                   is left enabled (the default), then compression will only
                   work if the zlib or zlib-dynamic options are also chosen.

  enable-crypto-mdebug
                   Build support for debugging memory allocated via
                   OPENSSL_malloc() or OPENSSL_zalloc().

  enable-crypto-mdebug-backtrace
                   As for crypto-mdebug, but additionally provide backtrace
                   information for allocated memory.
                   TO BE USED WITH CARE: this uses GNU C functionality, and
                   is therefore not usable for non-GNU config targets.  If
                   your build complains about the use of '-rdynamic' or the
                   lack of header file execinfo.h, this option is not for you.
                   ALSO NOTE that even though execinfo.h is available on your
                   system (through Gnulib), the functions might just be stubs
                   that do nothing.

  no-ct
                   Don't build support for Certificate Transparency.

  no-deprecated
                   Don't build with support for any deprecated APIs. This is the
                   same as using "--api" and supplying the latest version
                   number.

  no-dgram
                   Don't build support for datagram based BIOs. Selecting this
                   option will also force the disabling of DTLS.

  no-dso
                   Don't build support for loading Dynamic Shared Objects.

  no-dynamic-engine
                   Don't build the dynamically loaded engines. This only has an
                   effect in a "shared" build

  no-ec
                   Don't build support for Elliptic Curves.

  no-ec2m
                   Don't build support for binary Elliptic Curves

  enable-ec_nistp_64_gcc_128
                   Enable support for optimised implementations of some commonly
                   used NIST elliptic curves. This is only supported on some
                   platforms.

  enable-egd
                   Build support for gathering entropy from EGD (Entropy
                   Gathering Daemon).

  no-engine
                   Don't build support for loading engines.

  no-err
                   Don't compile in any error strings.

  no-filenames
                   Don't compile in filename and line number information (e.g.
                   for errors and memory allocation).

  enable-fuzz
                   Build with support for fuzzing. This is a developer option
                   only. It may not work on all platforms and should never be
                   used in production environments. See the file fuzz/README.md
                   for further details.

  no-gost
                   Don't build support for GOST based ciphersuites. Note that
                   if this feature is enabled then GOST ciphersuites are only
                   available if the GOST algorithms are also available through
                   loading an externally supplied engine.

  enable-heartbeats
                   Build support for DTLS heartbeats.

  no-hw-padlock
                   Don't build the padlock engine.

  no-makedepend
                   Don't generate dependencies.

  no-multiblock
                   Don't build support for writing multiple records in one
                   go in libssl (Note: this is a different capability to the
                   pipelining functionality).

  no-nextprotoneg
                   Don't build support for the NPN TLS extension.

  no-ocsp
                   Don't build support for OCSP.

  no-pic
                   Don't build with support for Position Independent Code.

  no-posix-io
                   Don't use POSIX IO capabilities.

  no-psk
                   Don't build support for Pre-Shared Key based ciphersuites.

  no-rdrand
                   Don't use hardware RDRAND capabilities.

  no-rfc3779
                   Don't build support for RFC3779 ("X.509 Extensions for IP
                   Addresses and AS Identifiers")

  sctp
                   Build support for SCTP

  no-shared
                   Do not create shared libraries, only static ones.  See "Note
                   on shared libraries" below.

  no-sock
                   Don't build support for socket BIOs

  no-srp
                   Don't build support for SRP or SRP based ciphersuites.

  no-srtp
                   Don't build SRTP support

  no-sse2
                   Exclude SSE2 code paths. Normally SSE2 extension is
                   detected at run-time, but the decision whether or not the
                   machine code will be executed is taken solely on CPU
                   capability vector. This means that if you happen to run OS
                   kernel which does not support SSE2 extension on Intel P4
                   processor, then your application might be exposed to
                   "illegal instruction" exception. There might be a way
                   to enable support in kernel, e.g. FreeBSD kernel can be
                   compiled with CPU_ENABLE_SSE, and there is a way to
                   disengage SSE2 code paths upon application start-up,
                   but if you aim for wider "audience" running such kernel,
                   consider no-sse2. Both the 386 and no-asm options imply
                   no-sse2.

  enable-ssl-trace
                   Build with the SSL Trace capabilities (adds the "-trace"
                   option to s_client and s_server).

  no-static-engine
                   Don't build the statically linked engines. This only
                   has an impact when not built "shared".

  no-stdio
                   Don't use any C "stdio" features. Only libcrypto and libssl
                   can be built in this way. Using this option will suppress
                   building the command line applications. Additionally since
                   the OpenSSL tests also use the command line applications the
                   tests will also be skipped.

  no-threads
                   Don't try to build with support for multi-threaded
                   applications.

  threads
                   Build with support for multi-threaded applications. Most
                   platforms will enable this by default. However if on a
                   platform where this is not the case then this will usually
                   require additional system-dependent options! See "Note on
                   multi-threading" below.

  no-ts
                   Don't build Time Stamping Authority support.

  enable-ubsan
                   Build with the Undefined Behaviour sanitiser. This is a
                   developer option only. It may not work on all platforms and
                   should never be used in production environments. It will only
                   work when used with gcc or clang and should be used in
                   conjunction with the "-DPEDANTIC" option (or the
                   --strict-warnings option).

  no-ui
                   Don't build with the "UI" capability (i.e. the set of
                   features enabling text based prompts).

  enable-unit-test
                   Enable additional unit test APIs. This should not typically
                   be used in production deployments.

  enable-weak-ssl-ciphers
                   Build support for SSL/TLS ciphers that are considered "weak"
                   (e.g. RC4 based ciphersuites).

  zlib
                   Build with support for zlib compression/decompression.

  zlib-dynamic
                   Like "zlib", but has OpenSSL load the zlib library
                   dynamically when needed.  This is only supported on systems
                   where loading of shared libraries is supported.

  386
                   On Intel hardware, use the 80386 instruction set only
                   (the default x86 code is more efficient, but requires at
                   least a 486). Note: Use compiler flags for any other CPU
                   specific configuration, e.g. "-m32" to build x86 code on
                   an x64 system.

  no-<prot>
                   Don't build support for negotiating the specified SSL/TLS
                   protocol (one of ssl, ssl3, tls, tls1, tls1_1, tls1_2, dtls,
                   dtls1 or dtls1_2). If "no-tls" is selected then all of tls1,
                   tls1_1 and tls1_2 are disabled. Similarly "no-dtls" will
                   disable dtls1 and dtls1_2. The "no-ssl" option is synonymous
                   with "no-ssl3". Note this only affects version negotiation.
                   OpenSSL will still provide the methods for applications to
                   explicitly select the individual protocol versions.

  no-<prot>-method
                   As for no-<prot> but in addition do not build the methods for
                   applications to explicitly select individual protocol
                   versions.

  enable-<alg>
                   Build with support for the specified algorithm, where <alg>
                   is one of: md2 or rc5.

  no-<alg>
                   Build without support for the specified algorithm, where
                   <alg> is one of: bf, blake2, camellia, cast, chacha, cmac,
                   des, dh, dsa, ecdh, ecdsa, idea, md4, md5, mdc2, ocb,
                   ploy1305, rc2, rc4, rmd160, scrypt, seed or whirlpool. The
                   "ripemd" algorithm is deprecated and if used is synonymous
                   with rmd160.

  -Dxxx, -lxxx, -Lxxx, -fxxx, -mXXX, -Kxxx
                   These system specific options will be passed through to the
                   compiler to allow you to define preprocessor symbols, specify
                   additional libraries, library directories or other compiler
                   options.


 Installation in Detail
 ----------------------

 1a. Configure OpenSSL for your operation system automatically:

     NOTE: This is not available on Windows.

       $ ./config [options]                             # Unix

       or

       $ @config [options]                              ! OpenVMS

     For the remainder of this text, the Unix form will be used in all
     examples, please use the appropriate form for your platform.

     This guesses at your operating system (and compiler, if necessary) and
     configures OpenSSL based on this guess. Run ./config -t to see
     if it guessed correctly. If you want to use a different compiler, you
     are cross-compiling for another platform, or the ./config guess was
     wrong for other reasons, go to step 1b. Otherwise go to step 2.

     On some systems, you can include debugging information as follows:

       $ ./config -d [options]

 1b. Configure OpenSSL for your operating system manually

     OpenSSL knows about a range of different operating system, hardware and
     compiler combinations. To see the ones it knows about, run

       $ ./Configure                                    # Unix

       or

       $ perl Configure                                 # All other platforms

     For the remainder of this text, the Unix form will be used in all
     examples, please use the appropriate form for your platform.

     Pick a suitable name from the list that matches your system. For most
     operating systems there is a choice between using "cc" or "gcc".  When
     you have identified your system (and if necessary compiler) use this name
     as the argument to Configure. For example, a "linux-elf" user would
     run:

       $ ./Configure linux-elf [options]

     If your system isn't listed, you will have to create a configuration
     file named Configurations/{something}.conf and add the correct
     configuration for your system. See the available configs as examples
     and read Configurations/README and Configurations/README.design for
     more information.

     The generic configurations "cc" or "gcc" should usually work on 32 bit
     Unix-like systems.

     Configure creates a build file ("Makefile" on Unix, "makefile" on Windows
     and "descrip.mms" on OpenVMS) from a suitable template in Configurations,
     and defines various macros in include/openssl/opensslconf.h (generated from
     include/openssl/opensslconf.h.in).

 1c. Configure OpenSSL for building outside of the source tree.

     OpenSSL can be configured to build in a build directory separate from
     the directory with the source code.  It's done by placing yourself in
     some other directory and invoking the configuration commands from
     there.

     Unix example:

       $ mkdir /var/tmp/openssl-build
       $ cd /var/tmp/openssl-build
       $ /PATH/TO/OPENSSL/SOURCE/config [options]

       or

       $ /PATH/TO/OPENSSL/SOURCE/Configure [target] [options]

     OpenVMS example:

       $ set default sys$login:
       $ create/dir [.tmp.openssl-build]
       $ set default [.tmp.openssl-build]
       $ @[PATH.TO.OPENSSL.SOURCE]config {options}

       or

       $ @[PATH.TO.OPENSSL.SOURCE]Configure {target} {options}

     Windows example:

       $ C:
       $ mkdir \temp-openssl
       $ cd \temp-openssl
       $ perl d:\PATH\TO\OPENSSL\SOURCE\Configure {target} {options}

     Paths can be relative just as well as absolute.  Configure will
     do its best to translate them to relative paths whenever possible.

  2. Build OpenSSL by running:

       $ make                                           # Unix
       $ mms                                            ! (or mmk) OpenVMS
       $ nmake                                          # Windows

     This will build the OpenSSL libraries (libcrypto.a and libssl.a on
     Unix, corresponding on other platforms) and the OpenSSL binary
     ("openssl"). The libraries will be built in the top-level directory,
     and the binary will be in the "apps" subdirectory.

     If the build fails, look at the output.  There may be reasons for
     the failure that aren't problems in OpenSSL itself (like missing
     standard headers).  If you are having problems you can get help by
     sending an email to the openssl-users email list (see
     https://www.openssl.org/community/mailinglists.html for details). If it
     is a bug with OpenSSL itself, please report the problem to
     <rt@openssl.org> (note that your message will be recorded in the request
     tracker publicly readable at
     https://www.openssl.org/community/index.html#bugs and will be
     forwarded to a public mailing list). Please check out the request
     tracker. Maybe the bug was already reported or has already been
     fixed.

     [If you encounter assembler error messages, try the "no-asm"
     configuration option as an immediate fix.]

     Compiling parts of OpenSSL with gcc and others with the system
     compiler will result in unresolved symbols on some systems.

  3. After a successful build, the libraries should be tested. Run:

       $ make test                                      # Unix
       $ mms test                                       ! OpenVMS
       $ nmake test                                     # Windows

     NOTE: you MUST run the tests from an unprivileged account (or
     disable your privileges temporarily if your platform allows it).

     If some tests fail, look at the output.  There may be reasons for
     the failure that isn't a problem in OpenSSL itself (like a
     malfunction with Perl).  You may want increased verbosity, that
     can be accomplished like this:

       $ make VERBOSE=1 test                            # Unix

       $ mms /macro=(VERBOSE=1) test                    ! OpenVMS

       $ nmake VERBOSE=1 test                           # Windows

     If you want to run just one or a few specific tests, you can use
     the make variable TESTS to specify them, like this:

       $ make TESTS='test_rsa test_dsa' test            # Unix
       $ mms/macro="TESTS=test_rsa test_dsa" test       ! OpenVMS
       $ nmake TESTS='test_rsa test_dsa' test           # Windows

     And of course, you can combine (Unix example shown):
       
       $ make VERBOSE=1 TESTS='test_rsa test_dsa' test

     You can find the list of available tests like this:

       $ make list-tests                                # Unix
       $ mms list-tests                                 ! OpenVMS
       $ nmake list-tests                               # Windows

     Have a look at the manual for the perl module Test::Harness to
     see what other HARNESS_* variables there are.

     If you find a problem with OpenSSL itself, try removing any
     compiler optimization flags from the CFLAGS line in Makefile and
     run "make clean; make" or corresponding.

     Please send bug reports to <rt@openssl.org>.

  4. If everything tests ok, install OpenSSL with

       $ make install                                   # Unix
       $ mms install                                    ! OpenVMS
       $ nmake install                                  # Windows

     This will install all the software components in this directory
     tree under PREFIX (the directory given with --prefix or its
     default):

       Unix:

         bin/           Contains the openssl binary and a few other
                        utility scripts.
         include/openssl
                        Contains the header files needed if you want
                        to build your own programs that use libcrypto
                        or libssl.
         lib            Contains the OpenSSL library files.
         lib/engines    Contains the OpenSSL dynamically loadable engines.
         share/man/{man1,man3,man5,man7}
                        Contains the OpenSSL man-pages.
         share/doc/openssl/html/{man1,man3,man5,man7}
                        Contains the HTML rendition of the man-pages.

       OpenVMS ('arch' is replaced with the architecture name, "Alpha"
       or "ia64"):

         [.EXE.'arch']  Contains the openssl binary and a few other
                        utility scripts.
         [.include.openssl]
                        Contains the header files needed if you want
                        to build your own programs that use libcrypto
                        or libssl.
         [.LIB.'arch']  Contains the OpenSSL library files.
         [.ENGINES.'arch']
                        Contains the OpenSSL dynamically loadable engines.
         [.SYS$STARTUP] Contains startup, login and shutdown scripts.
                        These define appropriate logical names and
                        command symbols.
                        

     Additionally, install will add the following directories under
     OPENSSLDIR (the directory given with --openssldir or its default)
     for you convenience:

         certs          Initially empty, this is the default location
                        for certificate files.
         private        Initially empty, this is the default location
                        for private key files.
         misc           Various scripts.

     Package builders who want to configure the library for standard
     locations, but have the package installed somewhere else so that
     it can easily be packaged, can use

       $ make DESTDIR=/tmp/package-root install         # Unix
       $ mms/macro="DESTDIR=TMP:[PACKAGE-ROOT]" install ! OpenVMS

     The specified destination directory will be prepended to all
     installation target paths.

  Compatibility issues with previous OpenSSL versions:

  *  COMPILING existing applications

     OpenSSL 1.1.0 hides a number of structures that were previously
     open.  This includes all internal libssl structures and a number
     of EVP types.  Accessor functions have been added to allow
     controlled access to the structures' data.

     This means that some software needs to be rewritten to adapt to
     the new ways of doing things.  This often amounts to allocating
     an instance of a structure explicitly where you could previously
     allocate them on the stack as automatic variables, and using the
     provided accessor functions where you would previously access a
     structure's field directly.

     Some APIs have changed as well.  However, older APIs have been
     preserved when possible.

 Environment Variables
 ---------------------

 A number of environment variables can be used to provide additional control
 over the build process. Typically these should be defined prior to running
 config or Configure. Not all environment variables are relevant to all
 platforms.

 AR
                The name of the ar executable to use.

 CC
                The compiler to use. Configure will attempt to pick a default
                compiler for your platform but this choice can be overridden
                using this variable. Set it to the compiler executable you wish
                to use, e.g. "gcc" or "clang".

 CROSS_COMPILE
                This environment variable has the same meaning as for the
                "--cross-compile-prefix" Configure flag described above. If both
                are set then the Configure flag takes precedence.

 NM
                The name of the nm executable to use.

 OPENSSL_LOCAL_CONFIG_DIR
                OpenSSL comes with a database of information about how it
                should be built on different platforms. This information is
                held in ".conf" files in the Configurations directory. See the
                file Configurations/README for further information about the
                format of ".conf" files. As well as the standard ".conf" files
                it is possible to create your own ".conf" files and store them
                locally, outside the OpenSSL source tree. This environment
                variable can be set to the directory where these files are held.

 PERL
                The name of the Perl executable to use when building OpenSSL.

 HASHBANGPERL
                The command string for the Perl executable to insert in the
                #! line of perl scripts that will be publically installed.
                Default: /usr/bin/env perl
                Note: the value of this variable is added to the same scripts
                on all platforms, but it's only relevant on Unix-like platforms.

 RC
                The name of the rc executable to use. The default will be as
                defined for the target platform in the ".conf" file. If not
                defined then "windres" will be used. The WINDRES environment
                variable is synonymous to this. If both are defined then RC
                takes precedence.

 RANLIB
                The name of the ranlib executable to use.

 WINDRES
                See RC.

 Makefile targets
 ----------------

 The Configure script generates a Makefile in a format relevant to the specific
 platform. The Makefiles provide a number of targets that can be used. Not all
 targets may be available on all platforms. Only the most common targets are
 described here. Examine the Makefiles themselves for the full list.

 all
                The default target to build all the software components.

 clean
                Remove all build artefacts and return the directory to a "clean"
                state.

 depend
                Rebuild the dependencies in the Makefiles. This is a legacy
                option that no longer needs to be used in OpenSSL 1.1.0.

 install
                Install all OpenSSL components.

 install_sw
                Only install the OpenSSL software components.

 install_docs
                Only install the OpenSSL documentation components.

 install_man_docs
                Only install the OpenSSL man pages (Unix only).

 install_html_docs
                Only install the OpenSSL html documentation.

 list-tests
                Prints a list of all the self test names.

 test
                Build and run the OpenSSL self tests.

 uninstall
                Uninstall all OpenSSL components.

 update
                This is a developer option. If you are developing a patch for
                OpenSSL you may need to use this if you want to update
                automatically generated files; add new error codes or add new
                (or change the visibility of) public API functions. (Unix only).

 Note on multi-threading
 -----------------------

 For some systems, the OpenSSL Configure script knows what compiler options
 are needed to generate a library that is suitable for multi-threaded
 applications.  On these systems, support for multi-threading is enabled
 by default; use the "no-threads" option to disable (this should never be
 necessary).

 On other systems, to enable support for multi-threading, you will have
 to specify at least two options: "threads", and a system-dependent option.
 (The latter is "-D_REENTRANT" on various systems.)  The default in this
 case, obviously, is not to include support for multi-threading (but
 you can still use "no-threads" to suppress an annoying warning message
 from the Configure script.)

 OpenSSL provides built-in support for two threading models: pthreads (found on
 most UNIX/Linux systems), and Windows threads. No other threading models are
 supported. If your platform does not provide pthreads or Windows threads then
 you should Configure with the "no-threads" option.

 Note on shared libraries
 ------------------------

 For most systems the OpenSSL Configure script knows what is needed to
 build shared libraries for libcrypto and libssl. On these systems
 the shared libraries will be created by default. This can be suppressed and
 only static libraries created by using the "no-shared" option. On systems
 where OpenSSL does not know how to build shared libraries the "no-shared"
 option will be forced and only static libraries will be created.

 Note on random number generation
 --------------------------------

 Availability of cryptographically secure random numbers is required for
 secret key generation. OpenSSL provides several options to seed the
 internal PRNG. If not properly seeded, the internal PRNG will refuse
 to deliver random bytes and a "PRNG not seeded error" will occur.
 On systems without /dev/urandom (or similar) device, it may be necessary
 to install additional support software to obtain a random seed.
 Please check out the manual pages for RAND_add(), RAND_bytes(), RAND_egd(),
 and the FAQ for more information.