Configurations/README

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