Configurations of OpenSSL target platforms
------------------------------------------

Target configurations are a collection of facts that we know about
different platforms and their capabilities.  We organise them in a
hash table, where each entry represent a specific target.

In each table entry, the following keys are significant:

        inherit_from    => Other targets to inherit values from.
                           Explained further below. [1]
        template        => Set to 1 if this isn't really a platform
                           target.  Instead, this target is a template
                           upon which other targets can be built.
                           Explained further below.  [1]

        sys_id          => System identity for systems where that
                           is difficult to determine automatically.

        cc              => The compiler command, usually one of "cc",
                           "gcc" or "clang".  This command is normally
                           also used to link object files and
                           libraries into the final program.
        cflags          => Flags that are used at all times when
                           compiling.
        debug_cflags    => Extra compilation flags used when making a
                           debug build (when Configure receives the
                           --debug option).  Typically something like
                           "-g -O0".
        release_cflags  => Extra compilation flags used when making a
                           release build (when Configure receives the
                           --release option, or doesn't receive the
                           --debug option).  Typically something like
                           "-O" or "-O3".
        thread_cflags   => Extra compilation flags used when
                           compiling with threading enabled.
                           Explained further below.  [2]
        shared_cflag    => Extra compilation flags used when
                           compiling for shared libraries, typically
                           something like "-fPIC".

        ld              => the linker command, usually not defined
                           (meaning the compiler command is used
                           instead).
                           (NOTE: this is here for future use, it's
                           not implemented yet)
        lflags          => the flags that are used at all times when
                           linking.  These can have a % sign in them
                           showing where the OpenSSL libraries should
                           appear, otherwise these flags will come
                           last.  So in a typical links situation,
                           this is a quick table of results:

                           "-foo%-bar"  > -foo -lssl -lcrypto -bar
                           "-foo%"      > -foo -lssl -lcrypto
                           "-foo"       > -lssl -lcrypto -foo

        debug_lflags    => Like debug_cflags, but used when linking.
        release_lflags  => Like release_cflags, but used when linking.
        shared_lflags   => Like shared_cflags, but used when linking.

        ar              => The library archive command, the default is
                           "ar".
                           (NOTE: this is here for future use, it's
                           not implemented yet)
        arflags         => Flags to be used with the library archive
                           command.

        ranlib          => The library archive indexing command, the
                           default is 'ranlib' it it exists.

        unistd          => An alternative header to the typical
                           '<unistd.h>'.  This is very rarely needed.

        shared_extension => File name extension used for shared
                            libraries. 
        obj_extension   => File name extension used for object files.
                           On unix, this defaults to ".o" (NOTE: this
                           is here for future use, it's not
                           implemented yet)
        exe_extension   => File name extension used for executable
                           files.  On unix, this defaults to "" (NOTE:
                           this is here for future use, it's not
                           implemented yet)

        dso_scheme      => The type of dynamic shared objects to build
                           for.  This mostly comes into play with
                           engines, but can be used for other purposes
                           as well.  Valid values are "DLFCN"
                           (dlopen() et al), "DLFCN_NO_H" (for systems
                           that use dlopen() et al but do not have
                           fcntl.h), "DL" (shl_load() et al), "WIN32"
                           and "VMS".
        perlasm_scheme  => The perlasm method used to created the
                           assembler files used when compiling with
                           assembler implementations.
        shared_target   => The shared library building method used.
                           This is a target found in Makefile.shared.
        build_scheme    => The scheme used to build up a Makefile.
                           In its simplest form, the value is a string
                           with the name of the build scheme.
                           The value may also take the form of a list
                           of strings, if the build_scheme is to have
                           some options.  In this case, the first
                           string in the list is the name of the build
                           scheme.
                           Currently recognised build schemes are
                           "mk1mf" and "unixmake" and "unified".
                           For the "unified" build scheme, this item
                           *must* be an array with the first being the
                           word "unified" and the second being a word
                           to identify the platform family.

        multilib        => On systems that support having multiple
                           implementations of a library (typically a
                           32-bit and a 64-bit variant), this is used
                           to have the different variants in different
                           directories.

        bn_ops          => Building options (was just bignum options
                           in the earlier history of this option,
                           hence the name).  This a string of words
                           that describe properties on the designated
                           target platform, such as the type of
                           integers used to build up the bitnum,
                           different ways to implement certain ciphers
                           and so on.  To fully comprehend the
                           meaning, the best is to read the affected
                           source.
                           The valid words are:

                           BN_LLONG     use 'unsigned long long' in
                                        some bignum calculations.
                                        This has no value when
                                        SIXTY_FOUR_BIT or
                                        SIXTY_FOUR_BIT_LONG is given.
                           RC4_CHAR     makes the basic RC4 unit of
                                        calculation an unsigned char.
                           SIXTY_FOUR_BIT       processor registers
                                                are 64 bits, long is
                                                32 bits, long long is
                                                64 bits.
                           SIXTY_FOUR_BIT_LONG  processor registers
                                                are 64 bits, long is
                                                64 bits.
                           THIRTY_TWO_BIT       processor registers
                                                are 32 bits.
                           EXPORT_VAR_AS_FN     for shared libraries,
                                                export vars as
                                                accessor functions.

        cpuid_asm_src   => assembler implementation of cpuid code as
                           well as OPENSSL_cleanse().
                           Default to mem_clr.c
        bn_asm_src      => Assembler implementation of core bignum
                           functions.
                           Defaults to bn_asm.c
        ec_asm_src      => Assembler implementation of core EC
                           functions.
        des_asm_src     => Assembler implementation of core DES
                           encryption functions.
                           Defaults to 'des_enc.c fcrypt_b.c'
        aes_asm_src     => Assembler implementation of core AES
                           functions.
                           Defaults to 'aes_core.c aes_cbc.c'
        bf_asm_src      => Assembler implementation of core BlowFish
                           functions.
                           Defaults to 'bf_enc.c'
        md5_asm_src     => Assembler implementation of core MD5
                           functions.
        sha1_asm_src    => Assembler implementation of core SHA1,
                           functions, and also possibly SHA256 and
                           SHA512 ones.
        cast_asm_src    => Assembler implementation of core CAST
                           functions.
                           Defaults to 'c_enc.c'
        rc4_asm_src     => Assembler implementation of core RC4
                           functions.
                           Defaults to 'rc4_enc.c rc4_skey.c'
        rmd160_asm_src  => Assembler implementation of core RMD160
                           functions.
        rc5_asm_src     => Assembler implementation of core RC5
                           functions.
                           Defaults to 'rc5_enc.c'
        wp_asm_src      => Assembler implementation of core WHIRLPOOL
                           functions.
        cmll_asm_src    => Assembler implementation of core CAMELLIA
                           functions.
                           Defaults to 'camellia.c cmll_misc.c cmll_cbc.c'
        modes_asm_src   => Assembler implementation of cipher modes,
                           currently the functions gcm_gmult_4bit and
                           gcm_ghash_4bit.
        padlock_asm_src => Assembler implementation of core parts of
                           the padlock engine.  This is mandatory on
                           any platform where the padlock engine might
                           actually be built.


[1] as part of the target configuration, one can have a key called
    'inherit_from' that indicate what other configurations to inherit
    data from.  These are resolved recursively.

    Inheritance works as a set of default values that can be overriden
    by corresponding key values in the inheriting configuration.

    Note 1: any configuration table can be used as a template.
    Note 2: pure templates have the attribute 'template => 1' and
            cannot be used as build targets.

    If several configurations are given in the 'inherit_from' array,
    the values of same attribute are concatenated with space
    separation.  With this, it's possible to have several smaller
    templates for different configuration aspects that can be combined
    into a complete configuration.

    instead of a scalar value or an array, a value can be a code block
    of the form 'sub { /* your code here */ }'.  This code block will
    be called with the list of inherited values for that key as
    arguments.  In fact, the concatenation of strings is really done
    by using 'sub { join(" ",@_) }' on the list of inherited values.

    An example:

        "foo" => {
                template => 1,
                haha => "ha ha",
                hoho => "ho",
                ignored => "This should not appear in the end result",
        },
        "bar" => {
                template => 1,
                haha => "ah",
                hoho => "haho",
                hehe => "hehe"
        },
        "laughter" => {
                inherit_from => [ "foo", "bar" ],
                hehe => sub { join(" ",(@_,"!!!")) },
                ignored => "",
        }

        The entry for "laughter" will become as follows after processing:

        "laughter" => {
                haha => "ha ha ah",
                hoho => "ho haho",
                hehe => "hehe !!!",
                ignored => ""
        }

[2] OpenSSL is built with threading capabilities unless the user
    specifies 'no-threads'.  The value of the key 'thread_cflags' may
    be "(unknown)", in which case the user MUST give some compilation
    flags to Configure.


Historically, the target configurations came in form of a string with
values separated by colons.  This use is deprecated.  The string form
looked like this:

   "target" => "{cc}:{cflags}:{unistd}:{thread_cflag}:{sys_id}:{lflags}:{bn_ops}:{cpuid_obj}:{bn_obj}:{ec_obj}:{des_obj}:{aes_obj}:{bf_obj}:{md5_obj}:{sha1_obj}:{cast_obj}:{rc4_obj}:{rmd160_obj}:{rc5_obj}:{wp_obj}:{cmll_obj}:{modes_obj}:{padlock_obj}:{perlasm_scheme}:{dso_scheme}:{shared_target}:{shared_cflag}:{shared_ldflag}:{shared_extension}:{ranlib}:{arflags}:{multilib}"


Build info files
================

The build.info files that are spread over the source tree contain the
minimum information needed to build and distribute OpenSSL.  It uses a
simple and yet fairly powerful language to determine what needs to be
built, from what sources, and other relationships between files.

For every build.info file, all file references are relative to the
directory of the build.info file for source files, and the
corresponding build directory for built files if the build tree
differs from the source tree.

When processed, every line is processed with the perl module
Text::Template, using the delimiters "{-" and "-}".  The hashes
%config and %target are passed to the perl fragments, along with
$sourcedir and $builddir, which are the locations of the source
directory for the current build.info file and the corresponding build
directory, all relative to the top of the build tree.

To begin with, things to be built are declared by setting specific
variables:

    PROGRAMS=foo bar
    LIBS=libsomething
    ENGINES=libeng
    SCRIPTS=myhack
    EXTRA=file1 file2

Note that the files mentioned for PROGRAMS, LIBS and ENGINES *must* be
without extensions.  The build file templates will figure them out.

For each thing to be built, it is then possible to say what sources
they are built from:

    PROGRAMS=foo bar
    SOURCE[foo]=foo.c common.c
    SOURCE[bar]=bar.c extra.c common.c

It's also possible to tell some other dependencies:

    DEPEND[foo]=libsomething
    DEPEND[libbar]=libsomethingelse

(it could be argued that 'libsomething' and 'libsomethingelse' are
source as well.  However, the files given through SOURCE are expected
to be located in the source tree while files given through DEPEND are
expected to be located in the build tree)

For some libraries, we maintain files with public symbols and their
slot in a transfer vector (important on some platforms).  It can be
declared like this:

    ORDINALS[libcrypto]=crypto

The value is not the name of the file in question, but rather the
argument to util/mkdef.pl that indicates which file to use.

One some platforms, shared libraries come with a name that's different
from their static counterpart.  That's declared as follows:

    SHARED_NAME[libfoo]=cygfoo-{- $config{shlibver} -}

The example is from Cygwin, which has a required naming convention.

Sometimes, it makes sense to rename an output file, for example a
library:

    RENAME[libfoo]=libbar

That lines has "libfoo" get renamed to "libbar".  While it makes no
sense at all to just have a rename like that (why not just use
"libbar" everywhere?), it does make sense when it can be used
conditionally.  See a little further below for an example.

For any file to be built, it's also possible to tell what extra
include paths the build of their source files should use:

    INCLUDE[foo]=include

It's possible to have raw build file lines, between BEGINRAW and
ENDRAW lines as follows:

    BEGINRAW[Makefile(unix)]
    haha.h: {- $builddir -}/Makefile
        echo "/* haha */" > haha.h
    ENDRAW[Makefile(unix)]

The word withing square brackets is the build_file configuration item
or the build_file configuration item followed by the second word in the
build_scheme configuration item for the configured target within
parenthesis as shown above.  For example, with the following relevant
configuration items:

   build_file   => "build.ninja"
   build_scheme => [ "unified", "unix" ]

... these lines will be considered:

   BEGINRAW[build.ninja]
   build haha.h: echo "/* haha */" > haha.h
   ENDRAW[build.ninja]

   BEGINRAW[build.ninja(unix)]
   build hoho.h: echo "/* hoho */" > hoho.h
   ENDRAW[build.ninja(unix)]

See the documentation further up for more information on configuration
items.

Finally, you can have some simple conditional use of the build.info
information, looking like this:

    IF[1]
     something
    ELSIF[2]
     something other
    ELSE
     something else
    ENDIF

The expression in square brackets is interpreted as a string in perl,
and will be seen as true if perl thinks it is, otherwise false.  For
example, the above would have "something" used, since 1 is true.

Together with the use of Text::Template, this can be used as
conditions based on something in the passed variables, for example:

    IF[{- $config{no_shared} -}]
      LIBS=libcrypto
      SOURCE[libcrypto]=...
    ELSE
      LIBS=libfoo
      SOURCE[libfoo]=...
    ENDIF

or:

    # VMS has a cultural standard where all libraries are prefixed.
    # For OpenSSL, the choice is 'ossl_'
    IF[{- $config{target} =~ /^vms/ -}]
     RENAME[libcrypto]=ossl_libcrypto
     RENAME[libssl]=ossl_libssl
    ENDIF