Configurations/README

   1 Intro
   2 =====
   3
   4 This directory contains a few sets of files that are used for
   5 configuration in diverse ways:
   6
   7     *.conf      Target platform configurations, please read
   8                 'Configurations of OpenSSL target platforms' for more
   9                 information.
  10     *.tmpl      Build file templates, please read 'Build-file
  11                 programming with the "unified" build system' as well
  12                 as 'Build info files' for more information.
  13     *.pm        Helper scripts / modules for the main `Configure`
  14                 script.  See 'Configure helper scripts for more
  15                 information.
  16
  17
  18 Configurations of OpenSSL target platforms
  19 ==========================================
  20
  21 Configuration targets are a collection of facts that we know about
  22 different platforms and their capabilities.  We organise them in a
  23 hash table, where each entry represent a specific target.
  24
  25 Note that configuration target names must be unique across all config
  26 files.  The Configure script does check that a config file doesn't
  27 have config targets that shadow config targets from other files.
  28
  29 In each table entry, the following keys are significant:
  30
  31         inherit_from    => Other targets to inherit values from.
  32                            Explained further below. [1]
  33         template        => Set to 1 if this isn't really a platform
  34                            target.  Instead, this target is a template
  35                            upon which other targets can be built.
  36                            Explained further below.  [1]
  37
  38         sys_id          => System identity for systems where that
  39                            is difficult to determine automatically.
  40
  41         enable          => Enable specific configuration features.
  42                            This MUST be an array of words.
  43         disable         => Disable specific configuration features.
  44                            This MUST be an array of words.
  45                            Note: if the same feature is both enabled
  46                            and disabled, disable wins.
  47
  48         as              => The assembler command.  This is not always
  49                            used (for example on Unix, where the C
  50                            compiler is used instead).
  51         asflags         => Default assembler command flags [4].
  52         cpp             => The C preprocessor command, normally not
  53                            given, as the build file defaults are
  54                            usually good enough.
  55         cppflags        => Default C preprocessor flags [4].
  56         defines         => As an alternative, macro definitions may be
  57                            given here instead of in `cppflags' [4].
  58                            If given here, they MUST be as an array of
  59                            the string such as "MACRO=value", or just
  60                            "MACRO" for definitions without value.
  61         includes        => As an alternative, inclusion directories
  62                            may be given here instead of in `cppflags'
  63                            [4].  If given here, the MUST be an array
  64                            of strings, one directory specification
  65                            each.
  66         cc              => The C compiler command, usually one of "cc",
  67                            "gcc" or "clang".  This command is normally
  68                            also used to link object files and
  69                            libraries into the final program.
  70         cxx             => The C++ compiler command, usually one of
  71                            "c++", "g++" or "clang++".  This command is
  72                            also used when linking a program where at
  73                            least one of the object file is made from
  74                            C++ source.
  75         cflags          => Defaults C compiler flags [4].
  76         cxxflags        => Default  C++ compiler flags [4].  If unset,
  77                            it gets the same value as cflags.
  78
  79         (linking is a complex thing, see [3] below)
  80         ld              => Linker command, usually not defined
  81                            (meaning the compiler command is used
  82                            instead).
  83                            (NOTE: this is here for future use, it's
  84                            not implemented yet)
  85         lflags          => Default flags used when linking apps,
  86                            shared libraries or DSOs [4].
  87         ex_libs         => Extra libraries that are needed when
  88                            linking shared libraries, DSOs or programs.
  89                            The value is also assigned to Libs.private
  90                            in $(libdir)/pkgconfig/libcrypto.pc.
  91
  92         shared_cppflags => Extra C preprocessor flags used when
  93                            processing C files for shared libraries.
  94         shared_cflag    => Extra C compiler flags used when compiling
  95                            for shared libraries, typically something
  96                            like "-fPIC".
  97         shared_ldflag   => Extra linking flags used when linking
  98                            shared libraries.
  99         module_cppflags
 100         module_cflags
 101         module_ldflags  => Has the same function as the corresponding
 102                            `shared_' attributes, but for building DSOs.
 103                            When unset, they get the same values as the
 104                            corresponding `shared_' attributes.
 105
 106         ar              => The library archive command, the default is
 107                            "ar".
 108                            (NOTE: this is here for future use, it's
 109                            not implemented yet)
 110         arflags         => Flags to be used with the library archive
 111                            command.  On Unix, this includes the
 112                            command letter, 'r' by default.
 113
 114         ranlib          => The library archive indexing command, the
 115                            default is 'ranlib' it it exists.
 116
 117         unistd          => An alternative header to the typical
 118                            '<unistd.h>'.  This is very rarely needed.
 119
 120         shared_extension => File name extension used for shared
 121                             libraries.
 122         obj_extension   => File name extension used for object files.
 123                            On unix, this defaults to ".o" (NOTE: this
 124                            is here for future use, it's not
 125                            implemented yet)
 126         exe_extension   => File name extension used for executable
 127                            files.  On unix, this defaults to "" (NOTE:
 128                            this is here for future use, it's not
 129                            implemented yet)
 130         shlib_variant   => A "variant" identifier inserted between the base
 131                            shared library name and the extension.  On "unixy"
 132                            platforms (BSD, Linux, Solaris, MacOS/X, ...) this
 133                            supports installation of custom OpenSSL libraries
 134                            that don't conflict with other builds of OpenSSL
 135                            installed on the system.  The variant identifier
 136                            becomes part of the SONAME of the library and also
 137                            any symbol versions (symbol versions are not used or
 138                            needed with MacOS/X).  For example, on a system
 139                            where a default build would normally create the SSL
 140                            shared library as 'libssl.so -> libssl.so.1.1' with
 141                            the value of the symlink as the SONAME, a target
 142                            definition that sets 'shlib_variant => "-abc"' will
 143                            create 'libssl.so -> libssl-abc.so.1.1', again with
 144                            an SONAME equal to the value of the symlink.  The
 145                            symbol versions associated with the variant library
 146                            would then be 'OPENSSL_ABC_<version>' rather than
 147                            the default 'OPENSSL_<version>'. The string inserted
 148                            into symbol versions is obtained by mapping all
 149                            letters in the "variant" identifier to upper case
 150                            and all non-alphanumeric characters to '_'.
 151
 152         thread_scheme   => The type of threads is used on the
 153                            configured platform.  Currently known
 154                            values are "(unknown)", "pthreads",
 155                            "uithreads" (a.k.a solaris threads) and
 156                            "winthreads".  Except for "(unknown)", the
 157                            actual value is currently ignored but may
 158                            be used in the future.  See further notes
 159                            below [2].
 160         dso_scheme      => The type of dynamic shared objects to build
 161                            for.  This mostly comes into play with
 162                            engines, but can be used for other purposes
 163                            as well.  Valid values are "DLFCN"
 164                            (dlopen() et al), "DLFCN_NO_H" (for systems
 165                            that use dlopen() et al but do not have
 166                            fcntl.h), "DL" (shl_load() et al), "WIN32"
 167                            and "VMS".
 168         perlasm_scheme  => The perlasm method used to create the
 169                            assembler files used when compiling with
 170                            assembler implementations.
 171         shared_target   => The shared library building method used.
 172                            This serves multiple purposes:
 173                            - as index for targets found in shared_info.pl.
 174                            - as linker script generation selector.
 175                            To serve both purposes, the index for shared_info.pl
 176                            should end with '-shared', and this suffix will be
 177                            removed for use as a linker script generation
 178                            selector.  Note that the latter is only used if
 179                            'shared_defflag' is defined.
 180         build_scheme    => The scheme used to build up a Makefile.
 181                            In its simplest form, the value is a string
 182                            with the name of the build scheme.
 183                            The value may also take the form of a list
 184                            of strings, if the build_scheme is to have
 185                            some options.  In this case, the first
 186                            string in the list is the name of the build
 187                            scheme.
 188                            Currently recognised build scheme is "unified".
 189                            For the "unified" build scheme, this item
 190                            *must* be an array with the first being the
 191                            word "unified" and the second being a word
 192                            to identify the platform family.
 193
 194         multilib        => On systems that support having multiple
 195                            implementations of a library (typically a
 196                            32-bit and a 64-bit variant), this is used
 197                            to have the different variants in different
 198                            directories.
 199
 200         bn_ops          => Building options (was just bignum options in
 201                            the earlier history of this option, hence the
 202                            name). This is a string of words that describe
 203                            algorithms' implementation parameters that
 204                            are optimal for the designated target platform,
 205                            such as the type of integers used to build up
 206                            the bignum, different ways to implement certain
 207                            ciphers and so on. To fully comprehend the
 208                            meaning, the best is to read the affected
 209                            source.
 210                            The valid words are:
 211
 212                            THIRTY_TWO_BIT       bignum limbs are 32 bits,
 213                                                 this is default if no
 214                                                 option is specified, it
 215                                                 works on any supported
 216                                                 system [unless "wider"
 217                                                 limb size is implied in
 218                                                 assembly code];
 219                            BN_LLONG             bignum limbs are 32 bits,
 220                                                 but 64-bit 'unsigned long
 221                                                 long' is used internally
 222                                                 in calculations;
 223                            SIXTY_FOUR_BIT_LONG  bignum limbs are 64 bits
 224                                                 and sizeof(long) is 8;
 225                            SIXTY_FOUR_BIT       bignums limbs are 64 bits,
 226                                                 but execution environment
 227                                                 is ILP32;
 228                            RC4_CHAR             RC4 key schedule is made
 229                                                 up of 'unsigned char's;
 230                            RC4_INT              RC4 key schedule is made
 231                                                 up of 'unsigned int's;
 232                            EXPORT_VAR_AS_FN     for shared libraries,
 233                                                 export vars as
 234                                                 accessor functions.
 235
 236         apps_aux_src    => Extra source to build apps/openssl and other
 237                            apps, as needed by the target and that can be
 238                            collected in a library.
 239         apps_init_src   => Init source to build apps/openssl and other
 240                            apps, as needed by the target.  This code
 241                            cannot be placed in a library, as the rest
 242                            of the code isn't expected to link to it
 243                            explicitly.
 244         cpuid_asm_src   => assembler implementation of cpuid code as
 245                            well as OPENSSL_cleanse().
 246                            Default to mem_clr.c
 247         bn_asm_src      => Assembler implementation of core bignum
 248                            functions.
 249                            Defaults to bn_asm.c
 250         ec_asm_src      => Assembler implementation of core EC
 251                            functions.
 252         des_asm_src     => Assembler implementation of core DES
 253                            encryption functions.
 254                            Defaults to 'des_enc.c fcrypt_b.c'
 255         aes_asm_src     => Assembler implementation of core AES
 256                            functions.
 257                            Defaults to 'aes_core.c aes_cbc.c'
 258         bf_asm_src      => Assembler implementation of core BlowFish
 259                            functions.
 260                            Defaults to 'bf_enc.c'
 261         md5_asm_src     => Assembler implementation of core MD5
 262                            functions.
 263         sha1_asm_src    => Assembler implementation of core SHA1,
 264                            functions, and also possibly SHA256 and
 265                            SHA512 ones.
 266         cast_asm_src    => Assembler implementation of core CAST
 267                            functions.
 268                            Defaults to 'c_enc.c'
 269         rc4_asm_src     => Assembler implementation of core RC4
 270                            functions.
 271                            Defaults to 'rc4_enc.c rc4_skey.c'
 272         rmd160_asm_src  => Assembler implementation of core RMD160
 273                            functions.
 274         rc5_asm_src     => Assembler implementation of core RC5
 275                            functions.
 276                            Defaults to 'rc5_enc.c'
 277         wp_asm_src      => Assembler implementation of core WHIRLPOOL
 278                            functions.
 279         cmll_asm_src    => Assembler implementation of core CAMELLIA
 280                            functions.
 281                            Defaults to 'camellia.c cmll_misc.c cmll_cbc.c'
 282         modes_asm_src   => Assembler implementation of cipher modes,
 283                            currently the functions gcm_gmult_4bit and
 284                            gcm_ghash_4bit.
 285         padlock_asm_src => Assembler implementation of core parts of
 286                            the padlock engine.  This is mandatory on
 287                            any platform where the padlock engine might
 288                            actually be built.
 289
 290
 291 [1] as part of the target configuration, one can have a key called
 292     'inherit_from' that indicate what other configurations to inherit
 293     data from.  These are resolved recursively.
 294
 295     Inheritance works as a set of default values that can be overridden
 296     by corresponding key values in the inheriting configuration.
 297
 298     Note 1: any configuration table can be used as a template.
 299     Note 2: pure templates have the attribute 'template => 1' and
 300             cannot be used as build targets.
 301
 302     If several configurations are given in the 'inherit_from' array,
 303     the values of same attribute are concatenated with space
 304     separation.  With this, it's possible to have several smaller
 305     templates for different configuration aspects that can be combined
 306     into a complete configuration.
 307
 308     instead of a scalar value or an array, a value can be a code block
 309     of the form 'sub { /* your code here */ }'.  This code block will
 310     be called with the list of inherited values for that key as
 311     arguments.  In fact, the concatenation of strings is really done
 312     by using 'sub { join(" ",@_) }' on the list of inherited values.
 313
 314     An example:
 315
 316         "foo" => {
 317                 template => 1,
 318                 haha => "ha ha",
 319                 hoho => "ho",
 320                 ignored => "This should not appear in the end result",
 321         },
 322         "bar" => {
 323                 template => 1,
 324                 haha => "ah",
 325                 hoho => "haho",
 326                 hehe => "hehe"
 327         },
 328         "laughter" => {
 329                 inherit_from => [ "foo", "bar" ],
 330                 hehe => sub { join(" ",(@_,"!!!")) },
 331                 ignored => "",
 332         }
 333
 334         The entry for "laughter" will become as follows after processing:
 335
 336         "laughter" => {
 337                 haha => "ha ha ah",
 338                 hoho => "ho haho",
 339                 hehe => "hehe !!!",
 340                 ignored => ""
 341         }
 342
 343 [2] OpenSSL is built with threading capabilities unless the user
 344     specifies 'no-threads'.  The value of the key 'thread_scheme' may
 345     be "(unknown)", in which case the user MUST give some compilation
 346     flags to Configure.
 347
 348 [3] OpenSSL has three types of things to link from object files or
 349     static libraries:
 350
 351     - shared libraries; that would be libcrypto and libssl.
 352     - shared objects (sometimes called dynamic libraries);  that would
 353       be the engines.
 354     - applications; those are apps/openssl and all the test apps.
 355
 356     Very roughly speaking, linking is done like this (words in braces
 357     represent the configuration settings documented at the beginning
 358     of this file):
 359
 360     shared libraries:
 361         {ld} $(CFLAGS) {lflags} {shared_ldflag} -o libfoo.so \
 362             foo/something.o foo/somethingelse.o {ex_libs}
 363
 364     shared objects:
 365         {ld} $(CFLAGS) {lflags} {module_ldflags} -o libeng.so \
 366             blah1.o blah2.o -lcrypto {ex_libs}
 367
 368     applications:
 369         {ld} $(CFLAGS) {lflags} -o app \
 370             app1.o utils.o -lssl -lcrypto {ex_libs}
 371
 372 [4] There are variants of these attribute, prefixed with `lib_',
 373     `dso_' or `bin_'.  Those variants replace the unprefixed attribute
 374     when building library, DSO or program modules specifically.
 375
 376 Historically, the target configurations came in form of a string with
 377 values separated by colons.  This use is deprecated.  The string form
 378 looked like this:
 379
 380    "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}"
 381
 382
 383 Build info files
 384 ================
 385
 386 The build.info files that are spread over the source tree contain the
 387 minimum information needed to build and distribute OpenSSL.  It uses a
 388 simple and yet fairly powerful language to determine what needs to be
 389 built, from what sources, and other relationships between files.
 390
 391 For every build.info file, all file references are relative to the
 392 directory of the build.info file for source files, and the
 393 corresponding build directory for built files if the build tree
 394 differs from the source tree.
 395
 396 When processed, every line is processed with the perl module
 397 Text::Template, using the delimiters "{-" and "-}".  The hashes
 398 %config and %target are passed to the perl fragments, along with
 399 $sourcedir and $builddir, which are the locations of the source
 400 directory for the current build.info file and the corresponding build
 401 directory, all relative to the top of the build tree.
 402
 403 'Configure' only knows inherently about the top build.info file.  For
 404 any other directory that has one, further directories to look into
 405 must be indicated like this:
 406
 407     SUBDIRS=something someelse
 408
 409 On to things to be built; they are declared by setting specific
 410 variables:
 411
 412     PROGRAMS=foo bar
 413     LIBS=libsomething
 414     ENGINES=libeng
 415     SCRIPTS=myhack
 416     EXTRA=file1 file2
 417
 418 Note that the files mentioned for PROGRAMS, LIBS and ENGINES *must* be
 419 without extensions.  The build file templates will figure them out.
 420
 421 For each thing to be built, it is then possible to say what sources
 422 they are built from:
 423
 424     PROGRAMS=foo bar
 425     SOURCE[foo]=foo.c common.c
 426     SOURCE[bar]=bar.c extra.c common.c
 427
 428 It's also possible to tell some other dependencies:
 429
 430     DEPEND[foo]=libsomething
 431     DEPEND[libbar]=libsomethingelse
 432
 433 (it could be argued that 'libsomething' and 'libsomethingelse' are
 434 source as well.  However, the files given through SOURCE are expected
 435 to be located in the source tree while files given through DEPEND are
 436 expected to be located in the build tree)
 437
 438 It's also possible to depend on static libraries explicitly:
 439
 440     DEPEND[foo]=libsomething.a
 441     DEPEND[libbar]=libsomethingelse.a
 442
 443 This should be rarely used, and care should be taken to make sure it's
 444 only used when supported.  For example, native Windows build doesn't
 445 support building static libraries and DLLs at the same time, so using
 446 static libraries on Windows can only be done when configured
 447 'no-shared'.
 448
 449 One some platforms, shared libraries come with a name that's different
 450 from their static counterpart.  That's declared as follows:
 451
 452     SHARED_NAME[libfoo]=cygfoo-{- $config{shlibver} -}
 453
 454 The example is from Cygwin, which has a required naming convention.
 455
 456 Sometimes, it makes sense to rename an output file, for example a
 457 library:
 458
 459     RENAME[libfoo]=libbar
 460
 461 That line has "libfoo" renamed to "libbar".  While it makes no
 462 sense at all to just have a rename like that (why not just use
 463 "libbar" everywhere?), it does make sense when it can be used
 464 conditionally.  See a little further below for an example.
 465
 466 In some cases, it's desirable to include some source files in the
 467 shared form of a library only:
 468
 469     SHARED_SOURCE[libfoo]=dllmain.c
 470
 471 For any file to be built, it's also possible to tell what extra
 472 include paths the build of their source files should use:
 473
 474     INCLUDE[foo]=include
 475
 476 It's also possible to specify C macros that should be defined:
 477
 478     DEFINE[foo]=FOO BAR=1
 479
 480 In some cases, one might want to generate some source files from
 481 others, that's done as follows:
 482
 483     GENERATE[foo.s]=asm/something.pl $(CFLAGS)
 484     GENERATE[bar.s]=asm/bar.S
 485
 486 The value of each GENERATE line is a command line or part of it.
 487 Configure places no rules on the command line, except that the first
 488 item must be the generator file.  It is, however, entirely up to the
 489 build file template to define exactly how those command lines should
 490 be handled, how the output is captured and so on.
 491
 492 Sometimes, the generator file itself depends on other files, for
 493 example if it is a perl script that depends on other perl modules.
 494 This can be expressed using DEPEND like this:
 495
 496     DEPEND[asm/something.pl]=../perlasm/Foo.pm
 497
 498 There may also be cases where the exact file isn't easily specified,
 499 but an inclusion directory still needs to be specified.  INCLUDE can
 500 be used in that case:
 501
 502     INCLUDE[asm/something.pl]=../perlasm
 503
 504 NOTE: GENERATE lines are limited to one command only per GENERATE.
 505
 506 As a last resort, it's possible to have raw build file lines, between
 507 BEGINRAW and ENDRAW lines as follows:
 508
 509     BEGINRAW[Makefile(unix)]
 510     haha.h: {- $builddir -}/Makefile
 511         echo "/* haha */" > haha.h
 512     ENDRAW[Makefile(unix)]
 513
 514 The word within square brackets is the build_file configuration item
 515 or the build_file configuration item followed by the second word in the
 516 build_scheme configuration item for the configured target within
 517 parenthesis as shown above.  For example, with the following relevant
 518 configuration items:
 519
 520    build_file   => "build.ninja"
 521    build_scheme => [ "unified", "unix" ]
 522
 523 ... these lines will be considered:
 524
 525    BEGINRAW[build.ninja]
 526    build haha.h: echo "/* haha */" > haha.h
 527    ENDRAW[build.ninja]
 528
 529    BEGINRAW[build.ninja(unix)]
 530    build hoho.h: echo "/* hoho */" > hoho.h
 531    ENDRAW[build.ninja(unix)]
 532
 533 Should it be needed because the recipes within a RAW section might
 534 clash with those generated by Configure, it's possible to tell it
 535 not to generate them with the use of OVERRIDES, for example:
 536
 537     SOURCE[libfoo]=foo.c bar.c
 538
 539     OVERRIDES=bar.o
 540     BEGINRAW[Makefile(unix)]
 541     bar.o: bar.c
 542         $(CC) $(CFLAGS) -DSPECIAL -c -o $@ $<
 543     ENDRAW[Makefile(unix)]
 544
 545 See the documentation further up for more information on configuration
 546 items.
 547
 548 Finally, you can have some simple conditional use of the build.info
 549 information, looking like this:
 550
 551     IF[1]
 552      something
 553     ELSIF[2]
 554      something other
 555     ELSE
 556      something else
 557     ENDIF
 558
 559 The expression in square brackets is interpreted as a string in perl,
 560 and will be seen as true if perl thinks it is, otherwise false.  For
 561 example, the above would have "something" used, since 1 is true.
 562
 563 Together with the use of Text::Template, this can be used as
 564 conditions based on something in the passed variables, for example:
 565
 566     IF[{- $disabled{shared} -}]
 567       LIBS=libcrypto
 568       SOURCE[libcrypto]=...
 569     ELSE
 570       LIBS=libfoo
 571       SOURCE[libfoo]=...
 572     ENDIF
 573
 574 or:
 575
 576     # VMS has a cultural standard where all libraries are prefixed.
 577     # For OpenSSL, the choice is 'ossl_'
 578     IF[{- $config{target} =~ /^vms/ -}]
 579      RENAME[libcrypto]=ossl_libcrypto
 580      RENAME[libssl]=ossl_libssl
 581     ENDIF
 582
 583
 584 Build-file programming with the "unified" build system
 585 ======================================================
 586
 587 "Build files" are called "Makefile" on Unix-like operating systems,
 588 "descrip.mms" for MMS on VMS, "makefile" for nmake on Windows, etc.
 589
 590 To use the "unified" build system, the target configuration needs to
 591 set the three items 'build_scheme', 'build_file' and 'build_command'.
 592 In the rest of this section, we will assume that 'build_scheme' is set
 593 to "unified" (see the configurations documentation above for the
 594 details).
 595
 596 For any name given by 'build_file', the "unified" system expects a
 597 template file in Configurations/ named like the build file, with
 598 ".tmpl" appended, or in case of possible ambiguity, a combination of
 599 the second 'build_scheme' list item and the 'build_file' name.  For
 600 example, if 'build_file' is set to "Makefile", the template could be
 601 Configurations/Makefile.tmpl or Configurations/unix-Makefile.tmpl.
 602 In case both Configurations/unix-Makefile.tmpl and
 603 Configurations/Makefile.tmpl are present, the former takes
 604 precedence.
 605
 606 The build-file template is processed with the perl module
 607 Text::Template, using "{-" and "-}" as delimiters that enclose the
 608 perl code fragments that generate configuration-dependent content.
 609 Those perl fragments have access to all the hash variables from
 610 configdata.pem.
 611
 612 The build-file template is expected to define at least the following
 613 perl functions in a perl code fragment enclosed with "{-" and "-}".
 614 They are all expected to return a string with the lines they produce.
 615
 616     generatesrc - function that produces build file lines to generate
 617                   a source file from some input.
 618
 619                   It's called like this:
 620
 621                         generatesrc(src => "PATH/TO/tobegenerated",
 622                                     generator => [ "generatingfile", ... ]
 623                                     generator_incs => [ "INCL/PATH", ... ]
 624                                     generator_deps => [ "dep1", ... ]
 625                                     generator => [ "generatingfile", ... ]
 626                                     incs => [ "INCL/PATH", ... ],
 627                                     deps => [ "dep1", ... ],
 628                                     intent => one of "libs", "dso", "bin" );
 629
 630                   'src' has the name of the file to be generated.
 631                   'generator' is the command or part of command to
 632                   generate the file, of which the first item is
 633                   expected to be the file to generate from.
 634                   generatesrc() is expected to analyse and figure out
 635                   exactly how to apply that file and how to capture
 636                   the result.  'generator_incs' and 'generator_deps'
 637                   are include directories and files that the generator
 638                   file itself depends on.  'incs' and 'deps' are
 639                   include directories and files that are used if $(CC)
 640                   is used as an intermediary step when generating the
 641                   end product (the file indicated by 'src').  'intent'
 642                   indicates what the generated file is going to be
 643                   used for.
 644
 645     src2obj     - function that produces build file lines to build an
 646                   object file from source files and associated data.
 647
 648                   It's called like this:
 649
 650                         src2obj(obj => "PATH/TO/objectfile",
 651                                 srcs => [ "PATH/TO/sourcefile", ... ],
 652                                 deps => [ "dep1", ... ],
 653                                 incs => [ "INCL/PATH", ... ]
 654                                 intent => one of "lib", "dso", "bin" );
 655
 656                   'obj' has the intended object file with '.o'
 657                   extension, src2obj() is expected to change it to
 658                   something more suitable for the platform.
 659                   'srcs' has the list of source files to build the
 660                   object file, with the first item being the source
 661                   file that directly corresponds to the object file.
 662                   'deps' is a list of explicit dependencies.  'incs'
 663                   is a list of include file directories.  Finally,
 664                   'intent' indicates what this object file is going
 665                   to be used for.
 666
 667     obj2lib     - function that produces build file lines to build a
 668                   static library file ("libfoo.a" in Unix terms) from
 669                   object files.
 670
 671                   called like this:
 672
 673                         obj2lib(lib => "PATH/TO/libfile",
 674                                 objs => [ "PATH/TO/objectfile", ... ]);
 675
 676                   'lib' has the intended library file name *without*
 677                   extension, obj2lib is expected to add that.  'objs'
 678                   has the list of object files to build this library.
 679
 680     libobj2shlib - backward compatibility function that's used the
 681                   same way as obj2shlib (described next), and was
 682                   expected to build the shared library from the
 683                   corresponding static library when that was suitable.
 684                   NOTE: building a shared library from a static
 685                   library is now DEPRECATED, as they no longer share
 686                   object files.  Attempting to do this will fail.
 687
 688     obj2shlib   - function that produces build file lines to build a
 689                   shareable object library file ("libfoo.so" in Unix
 690                   terms) from the corresponding object files.
 691
 692                   called like this:
 693
 694                         obj2shlib(shlib => "PATH/TO/shlibfile",
 695                                   lib => "PATH/TO/libfile",
 696                                   objs => [ "PATH/TO/objectfile", ... ],
 697                                   deps => [ "PATH/TO/otherlibfile", ... ]);
 698
 699                   'lib' has the base (static) library ffile name
 700                   *without* extension.  This is useful in case
 701                   supporting files are needed (such as import
 702                   libraries on Windows).
 703                   'shlib' has the corresponding shared library name
 704                   *without* extension.  'deps' has the list of other
 705                   libraries (also *without* extension) this library
 706                   needs to be linked with.  'objs' has the list of
 707                   object files to build this library.
 708
 709     obj2dso     - function that produces build file lines to build a
 710                   dynamic shared object file from object files.
 711
 712                   called like this:
 713
 714                         obj2dso(lib => "PATH/TO/libfile",
 715                                 objs => [ "PATH/TO/objectfile", ... ],
 716                                 deps => [ "PATH/TO/otherlibfile",
 717                                 ... ]);
 718
 719                   This is almost the same as obj2shlib, but the
 720                   intent is to build a shareable library that can be
 721                   loaded in runtime (a "plugin"...).
 722
 723     obj2bin     - function that produces build file lines to build an
 724                   executable file from object files.
 725
 726                   called like this:
 727
 728                         obj2bin(bin => "PATH/TO/binfile",
 729                                 objs => [ "PATH/TO/objectfile", ... ],
 730                                 deps => [ "PATH/TO/libfile", ... ]);
 731
 732                   'bin' has the intended executable file name
 733                   *without* extension, obj2bin is expected to add
 734                   that.  'objs' has the list of object files to build
 735                   this library.  'deps' has the list of library files
 736                   (also *without* extension) that the programs needs
 737                   to be linked with.
 738
 739     in2script   - function that produces build file lines to build a
 740                   script file from some input.
 741
 742                   called like this:
 743
 744                         in2script(script => "PATH/TO/scriptfile",
 745                                   sources => [ "PATH/TO/infile", ... ]);
 746
 747                   'script' has the intended script file name.
 748                   'sources' has the list of source files to build the
 749                   resulting script from.
 750
 751 In all cases, file file paths are relative to the build tree top, and
 752 the build file actions run with the build tree top as current working
 753 directory.
 754
 755 Make sure to end the section with these functions with a string that
 756 you thing is appropriate for the resulting build file.  If nothing
 757 else, end it like this:
 758
 759       "";       # Make sure no lingering values end up in the Makefile
 760     -}
 761
 762
 763 Configure helper scripts
 764 ========================
 765
 766 Configure uses helper scripts in this directory:
 767
 768 Checker scripts
 769 ---------------
 770
 771 These scripts are per platform family, to check the integrity of the
 772 tools used for configuration and building.  The checker script used is
 773 either {build_platform}-{build_file}-checker.pm or
 774 {build_platform}-checker.pm, where {build_platform} is the second
 775 'build_scheme' list element from the configuration target data, and
 776 {build_file} is 'build_file' from the same target data.
 777
 778 If the check succeeds, the script is expected to end with a non-zero
 779 expression.  If the check fails, the script can end with a zero, or
 780 with a `die`.