Configurations/README-design.md

   1 Design document for the unified scheme data
   2 ===========================================
   3
   4 How are things connected?
   5 -------------------------
   6
   7 The unified scheme takes all its data from the `build.info` files seen
   8 throughout the source tree.  These files hold the minimum information
   9 needed to build end product files from diverse sources.  See the
  10 section on `build.info` files below.
  11
  12 From the information in `build.info` files, `Configure` builds up an
  13 information database as a hash table called `%unified_info`, which is
  14 stored in configdata.pm, found at the top of the build tree (which may
  15 or may not be the same as the source tree).
  16
  17 [`Configurations/common.tmpl`](common.tmpl) uses the data from `%unified_info` to
  18 generate the rules for building end product files as well as
  19 intermediary files with the help of a few functions found in the
  20 build-file templates.  See the section on build-file templates further
  21 down for more information.
  22
  23 build.info files
  24 ----------------
  25
  26 As mentioned earlier, `build.info` files are meant to hold the minimum
  27 information needed to build output files, and therefore only (with a
  28 few possible exceptions [1]) have information about end products (such
  29 as scripts, library files and programs) and source files (such as C
  30 files, C header files, assembler files, etc).  Intermediate files such
  31 as object files are rarely directly referred to in `build.info` files (and
  32 when they are, it's always with the file name extension `.o`), they are
  33 inferred by `Configure`.  By the same rule of minimalism, end product
  34 file name extensions (such as `.so`, `.a`, `.exe`, etc) are never mentioned
  35 in `build.info`.  Their file name extensions will be inferred by the
  36 build-file templates, adapted for the platform they are meant for (see
  37 sections on `%unified_info` and build-file templates further down).
  38
  39 The variables `PROGRAMS`, `LIBS`, `MODULES` and `SCRIPTS` are used to declare
  40 end products.  There are variants for them with `_NO_INST` as suffix
  41 (`PROGRAM_NO_INST` etc) to specify end products that shouldn't get installed.
  42
  43 The variables `SOURCE`, `DEPEND`, `INCLUDE` and `DEFINE` are indexed by a
  44 produced file, and their values are the source used to produce that
  45 particular produced file, extra dependencies, include directories
  46 needed, or C macros to be defined.
  47
  48 All their values in all the `build.info` throughout the source tree are
  49 collected together and form a set of programs, libraries, modules and
  50 scripts to be produced, source files, dependencies, etc etc etc.
  51
  52 Let's have a pretend example, a very limited contraption of OpenSSL,
  53 composed of the program `apps/openssl`, the libraries `libssl` and
  54 `libcrypto`, an module `engines/ossltest` and their sources and
  55 dependencies.
  56
  57     # build.info
  58     LIBS=libcrypto libssl
  59     INCLUDE[libcrypto]=include
  60     INCLUDE[libssl]=include
  61     DEPEND[libssl]=libcrypto
  62
  63 This is the top directory `build.info` file, and it tells us that two
  64 libraries are to be built, the include directory `include/` shall be
  65 used throughout when building anything that will end up in each
  66 library, and that the library `libssl` depend on the library
  67 `libcrypto` to function properly.
  68
  69     # apps/build.info
  70     PROGRAMS=openssl
  71     SOURCE[openssl]=openssl.c
  72     INCLUDE[openssl]=.. ../include
  73     DEPEND[openssl]=../libssl
  74
  75 This is the `build.info` file in `apps/`, one may notice that all file
  76 paths mentioned are relative to the directory the `build.info` file is
  77 located in.  This one tells us that there's a program to be built
  78 called `apps/openss` (the file name extension will depend on the
  79 platform and is therefore not mentioned in the `build.info` file).  It's
  80 built from one source file, `apps/openssl.c`, and building it requires
  81 the use of `.` and `include/` include directories (both are declared
  82 from the point of view of the `apps/` directory), and that the program
  83 depends on the library `libssl` to function properly.
  84
  85     # crypto/build.info
  86     LIBS=../libcrypto
  87     SOURCE[../libcrypto]=aes.c evp.c cversion.c
  88     DEPEND[cversion.o]=buildinf.h
  89
  90     GENERATE[buildinf.h]=../util/mkbuildinf.pl "$(CC) $(CFLAGS)" "$(PLATFORM)"
  91     DEPEND[buildinf.h]=../Makefile
  92     DEPEND[../util/mkbuildinf.pl]=../util/Foo.pm
  93
  94 This is the `build.info` file in `crypto/`, and it tells us a little more
  95 about what's needed to produce `libcrypto`.  LIBS is used again to
  96 declare that `libcrypto` is to be produced.  This declaration is
  97 really unnecessary as it's already mentioned in the top `build.info`
  98 file, but can make the info file easier to understand.  This is to
  99 show that duplicate information isn't an issue.
 100
 101 This `build.info` file informs us that `libcrypto` is built from a few
 102 source files, `crypto/aes.c`, `crypto/evp.c` and `crypto/cversion.c`.
 103 It also shows us that building the object file inferred from
 104 `crypto/cversion.c` depends on `crypto/buildinf.h`.  Finally, it
 105 also shows the possibility to declare how some files are generated
 106 using some script, in this case a perl script, and how such scripts
 107 can be declared to depend on other files, in this case a perl module.
 108
 109 Two things are worth an extra note:
 110
 111 `DEPEND[cversion.o]` mentions an object file.  DEPEND indexes is the
 112 only location where it's valid to mention them
 113
 114     # ssl/build.info
 115     LIBS=../libssl
 116     SOURCE[../libssl]=tls.c
 117
 118 This is the build.info file in `ssl/`, and it tells us that the
 119 library `libssl` is built from the source file `ssl/tls.c`.
 120
 121     # engines/build.info
 122     MODULES=dasync
 123     SOURCE[dasync]=e_dasync.c
 124     DEPEND[dasync]=../libcrypto
 125     INCLUDE[dasync]=../include
 126
 127     MODULES_NO_INST=ossltest
 128     SOURCE[ossltest]=e_ossltest.c
 129     DEPEND[ossltest]=../libcrypto.a
 130     INCLUDE[ossltest]=../include
 131
 132 This is the `build.info` file in `engines/`, telling us that two modules
 133 called `engines/dasync` and `engines/ossltest` shall be built, that
 134 `dasync`'s source is `engines/e_dasync.c` and `ossltest`'s source is
 135 `engines/e_ossltest.c` and that the include directory `include/` may
 136 be used when building anything that will be part of these modules.
 137 Also, both modules depend on the library `libcrypto` to function
 138 properly.  `ossltest` is explicitly linked with the static variant of
 139 the library `libcrypto`.  Finally, only `dasync` is being installed, as
 140 `ossltest` is only for internal testing.
 141
 142 When `Configure` digests these `build.info` files, the accumulated
 143 information comes down to this:
 144
 145     LIBS=libcrypto libssl
 146     SOURCE[libcrypto]=crypto/aes.c crypto/evp.c crypto/cversion.c
 147     DEPEND[crypto/cversion.o]=crypto/buildinf.h
 148     INCLUDE[libcrypto]=include
 149     SOURCE[libssl]=ssl/tls.c
 150     INCLUDE[libssl]=include
 151     DEPEND[libssl]=libcrypto
 152
 153     PROGRAMS=apps/openssl
 154     SOURCE[apps/openssl]=apps/openssl.c
 155     INCLUDE[apps/openssl]=. include
 156     DEPEND[apps/openssl]=libssl
 157
 158     MODULES=engines/dasync
 159     SOURCE[engines/dasync]=engines/e_dasync.c
 160     DEPEND[engines/dasync]=libcrypto
 161     INCLUDE[engines/dasync]=include
 162
 163     MODULES_NO_INST=engines/ossltest
 164     SOURCE[engines/ossltest]=engines/e_ossltest.c
 165     DEPEND[engines/ossltest]=libcrypto.a
 166     INCLUDE[engines/ossltest]=include
 167
 168     GENERATE[crypto/buildinf.h]=util/mkbuildinf.pl "$(CC) $(CFLAGS)" "$(PLATFORM)"
 169     DEPEND[crypto/buildinf.h]=Makefile
 170     DEPEND[util/mkbuildinf.pl]=util/Foo.pm
 171
 172 A few notes worth mentioning:
 173
 174 `LIBS` may be used to declare routine libraries only.
 175
 176 `PROGRAMS` may be used to declare programs only.
 177
 178 `MODULES` may be used to declare modules only.
 179
 180 The indexes for `SOURCE` must only be end product files, such as
 181 libraries, programs or modules.  The values of `SOURCE` variables must
 182 only be source files (possibly generated).
 183
 184 `INCLUDE` and `DEPEND` shows a relationship between different files
 185 (usually produced files) or between files and directories, such as a
 186 program depending on a library, or between an object file and some
 187 extra source file.
 188
 189 When `Configure` processes the `build.info` files, it will take it as
 190 truth without question, and will therefore perform very few checks.
 191 If the build tree is separate from the source tree, it will assume
 192 that all built files and up in the build directory and that all source
 193 files are to be found in the source tree, if they can be found there.
 194 `Configure` will assume that source files that can't be found in the
 195 source tree (such as `crypto/bildinf.h` in the example above) are
 196 generated and will be found in the build tree.
 197
 198 The `%unified_info` database
 199 ----------------------------
 200
 201 The information in all the `build.info` get digested by `Configure` and
 202 collected into the `%unified_info` database, divided into the following
 203 indexes:
 204
 205     depends   => a hash table containing 'file' => [ 'dependency' ... ]
 206                  pairs.  These are directly inferred from the DEPEND
 207                  variables in build.info files.
 208
 209     modules   => a list of modules.  These are directly inferred from
 210                  the MODULES variable in build.info files.
 211
 212     generate  => a hash table containing 'file' => [ 'generator' ... ]
 213                  pairs.  These are directly inferred from the GENERATE
 214                  variables in build.info files.
 215
 216     includes  => a hash table containing 'file' => [ 'include' ... ]
 217                  pairs.  These are directly inferred from the INCLUDE
 218                  variables in build.info files.
 219
 220     install   => a hash table containing 'type' => [ 'file' ... ] pairs.
 221                  The types are 'programs', 'libraries', 'modules' and
 222                  'scripts', and the array of files list the files of
 223                  that type that should be installed.
 224
 225     libraries => a list of libraries.  These are directly inferred from
 226                  the LIBS variable in build.info files.
 227
 228     programs  => a list of programs.  These are directly inferred from
 229                  the PROGRAMS variable in build.info files.
 230
 231     scripts   => a list of scripts.  There are directly inferred from
 232                  the SCRIPTS variable in build.info files.
 233
 234     sources   => a hash table containing 'file' => [ 'sourcefile' ... ]
 235                  pairs.  These are indirectly inferred from the SOURCE
 236                  variables in build.info files.  Object files are
 237                  mentioned in this hash table, with source files from
 238                  SOURCE variables, and AS source files for programs and
 239                  libraries.
 240
 241     shared_sources =>
 242                  a hash table just like 'sources', but only as source
 243                  files (object files) for building shared libraries.
 244
 245 As an example, here is how the `build.info` files example from the
 246 section above would be digested into a `%unified_info` table:
 247
 248     our %unified_info = (
 249         "depends" =>
 250             {
 251                 "apps/openssl" =>
 252                     [
 253                         "libssl",
 254                     ],
 255                 "crypto/buildinf.h" =>
 256                     [
 257                         "Makefile",
 258                     ],
 259                 "crypto/cversion.o" =>
 260                     [
 261                         "crypto/buildinf.h",
 262                     ],
 263                 "engines/dasync" =>
 264                     [
 265                         "libcrypto",
 266                     ],
 267                 "engines/ossltest" =>
 268                     [
 269                         "libcrypto.a",
 270                     ],
 271                 "libssl" =>
 272                     [
 273                         "libcrypto",
 274                     ],
 275                 "util/mkbuildinf.pl" =>
 276                     [
 277                         "util/Foo.pm",
 278                     ],
 279             },
 280         "modules" =>
 281             [
 282                 "engines/dasync",
 283                 "engines/ossltest",
 284             ],
 285         "generate" =>
 286             {
 287                 "crypto/buildinf.h" =>
 288                     [
 289                         "util/mkbuildinf.pl",
 290                         "\"\$(CC)",
 291                         "\$(CFLAGS)\"",
 292                         "\"$(PLATFORM)\"",
 293                     ],
 294             },
 295         "includes" =>
 296             {
 297                 "apps/openssl" =>
 298                     [
 299                         ".",
 300                         "include",
 301                     ],
 302                 "engines/ossltest" =>
 303                     [
 304                         "include"
 305                     ],
 306                 "libcrypto" =>
 307                     [
 308                         "include",
 309                     ],
 310                 "libssl" =>
 311                     [
 312                         "include",
 313                     ],
 314                 "util/mkbuildinf.pl" =>
 315                     [
 316                         "util",
 317                     ],
 318             }
 319         "install" =>
 320             {
 321                 "modules" =>
 322                     [
 323                         "engines/dasync",
 324                     ],
 325                 "libraries" =>
 326                     [
 327                         "libcrypto",
 328                         "libssl",
 329                     ],
 330                 "programs" =>
 331                     [
 332                         "apps/openssl",
 333                     ],
 334            },
 335         "libraries" =>
 336             [
 337                 "libcrypto",
 338                 "libssl",
 339             ],
 340         "programs" =>
 341             [
 342                 "apps/openssl",
 343             ],
 344         "sources" =>
 345             {
 346                 "apps/openssl" =>
 347                     [
 348                         "apps/openssl.o",
 349                     ],
 350                 "apps/openssl.o" =>
 351                     [
 352                         "apps/openssl.c",
 353                     ],
 354                 "crypto/aes.o" =>
 355                     [
 356                         "crypto/aes.c",
 357                     ],
 358                 "crypto/cversion.o" =>
 359                     [
 360                         "crypto/cversion.c",
 361                     ],
 362                 "crypto/evp.o" =>
 363                     [
 364                         "crypto/evp.c",
 365                     ],
 366                 "engines/e_dasync.o" =>
 367                     [
 368                         "engines/e_dasync.c",
 369                     ],
 370                 "engines/dasync" =>
 371                     [
 372                         "engines/e_dasync.o",
 373                     ],
 374                 "engines/e_ossltest.o" =>
 375                     [
 376                         "engines/e_ossltest.c",
 377                     ],
 378                 "engines/ossltest" =>
 379                     [
 380                         "engines/e_ossltest.o",
 381                     ],
 382                 "libcrypto" =>
 383                     [
 384                         "crypto/aes.c",
 385                         "crypto/cversion.c",
 386                         "crypto/evp.c",
 387                     ],
 388                 "libssl" =>
 389                     [
 390                         "ssl/tls.c",
 391                     ],
 392                 "ssl/tls.o" =>
 393                     [
 394                         "ssl/tls.c",
 395                     ],
 396             },
 397     );
 398
 399 As can be seen, everything in `%unified_info` is fairly simple suggest
 400 of information.  Still, it tells us that to build all programs, we
 401 must build `apps/openssl`, and to build the latter, we will need to
 402 build all its sources (`apps/openssl.o` in this case) and all the
 403 other things it depends on (such as `libssl`).  All those dependencies
 404 need to be built as well, using the same logic, so to build `libssl`,
 405 we need to build `ssl/tls.o` as well as `libcrypto`, and to build the
 406 latter...
 407
 408 Build-file templates
 409 --------------------
 410
 411 Build-file templates are essentially build-files (such as `Makefile` on
 412 Unix) with perl code fragments mixed in.  Those perl code fragment
 413 will generate all the configuration dependent data, including all the
 414 rules needed to build end product files and intermediary files alike.
 415 At a minimum, there must be a perl code fragment that defines a set of
 416 functions that are used to generates specific build-file rules, to
 417 build static libraries from object files, to build shared libraries
 418 from static libraries, to programs from object files and libraries,
 419 etc.
 420
 421     generatesrc - function that produces build file lines to generate
 422                   a source file from some input.
 423
 424                   It's called like this:
 425
 426                         generatesrc(src => "PATH/TO/tobegenerated",
 427                                     generator => [ "generatingfile", ... ]
 428                                     generator_incs => [ "INCL/PATH", ... ]
 429                                     generator_deps => [ "dep1", ... ]
 430                                     incs => [ "INCL/PATH", ... ],
 431                                     deps => [ "dep1", ... ],
 432                                     intent => one of "libs", "dso", "bin" );
 433
 434                   'src' has the name of the file to be generated.
 435                   'generator' is the command or part of command to
 436                   generate the file, of which the first item is
 437                   expected to be the file to generate from.
 438                   generatesrc() is expected to analyse and figure out
 439                   exactly how to apply that file and how to capture
 440                   the result.  'generator_incs' and 'generator_deps'
 441                   are include directories and files that the generator
 442                   file itself depends on.  'incs' and 'deps' are
 443                   include directories and files that are used if $(CC)
 444                   is used as an intermediary step when generating the
 445                   end product (the file indicated by 'src').  'intent'
 446                   indicates what the generated file is going to be
 447                   used for.
 448
 449     src2obj     - function that produces build file lines to build an
 450                   object file from source files and associated data.
 451
 452                   It's called like this:
 453
 454                         src2obj(obj => "PATH/TO/objectfile",
 455                                 srcs => [ "PATH/TO/sourcefile", ... ],
 456                                 deps => [ "dep1", ... ],
 457                                 incs => [ "INCL/PATH", ... ]
 458                                 intent => one of "lib", "dso", "bin" );
 459
 460                   'obj' has the intended object file with `.o`
 461                   extension, src2obj() is expected to change it to
 462                   something more suitable for the platform.
 463                   'srcs' has the list of source files to build the
 464                   object file, with the first item being the source
 465                   file that directly corresponds to the object file.
 466                   'deps' is a list of explicit dependencies.  'incs'
 467                   is a list of include file directories.  Finally,
 468                   'intent' indicates what this object file is going
 469                   to be used for.
 470
 471     obj2lib     - function that produces build file lines to build a
 472                   static library file ("libfoo.a" in Unix terms) from
 473                   object files.
 474
 475                   called like this:
 476
 477                         obj2lib(lib => "PATH/TO/libfile",
 478                                 objs => [ "PATH/TO/objectfile", ... ]);
 479
 480                   'lib' has the intended library file name *without*
 481                   extension, obj2lib is expected to add that.  'objs'
 482                   has the list of object files to build this library.
 483
 484     libobj2shlib - backward compatibility function that's used the
 485                   same way as obj2shlib (described next), and was
 486                   expected to build the shared library from the
 487                   corresponding static library when that was suitable.
 488                   NOTE: building a shared library from a static
 489                   library is now DEPRECATED, as they no longer share
 490                   object files.  Attempting to do this will fail.
 491
 492     obj2shlib   - function that produces build file lines to build a
 493                   shareable object library file ("libfoo.so" in Unix
 494                   terms) from the corresponding object files.
 495
 496                   called like this:
 497
 498                         obj2shlib(shlib => "PATH/TO/shlibfile",
 499                                   lib => "PATH/TO/libfile",
 500                                   objs => [ "PATH/TO/objectfile", ... ],
 501                                   deps => [ "PATH/TO/otherlibfile", ... ]);
 502
 503                   'lib' has the base (static) library file name
 504                   *without* extension.  This is useful in case
 505                   supporting files are needed (such as import
 506                   libraries on Windows).
 507                   'shlib' has the corresponding shared library name
 508                   *without* extension.  'deps' has the list of other
 509                   libraries (also *without* extension) this library
 510                   needs to be linked with.  'objs' has the list of
 511                   object files to build this library.
 512
 513     obj2dso     - function that produces build file lines to build a
 514                   dynamic shared object file from object files.
 515
 516                   called like this:
 517
 518                         obj2dso(lib => "PATH/TO/libfile",
 519                                 objs => [ "PATH/TO/objectfile", ... ],
 520                                 deps => [ "PATH/TO/otherlibfile",
 521                                 ... ]);
 522
 523                   This is almost the same as obj2shlib, but the
 524                   intent is to build a shareable library that can be
 525                   loaded in runtime (a "plugin"...).
 526
 527     obj2bin     - function that produces build file lines to build an
 528                   executable file from object files.
 529
 530                   called like this:
 531
 532                         obj2bin(bin => "PATH/TO/binfile",
 533                                 objs => [ "PATH/TO/objectfile", ... ],
 534                                 deps => [ "PATH/TO/libfile", ... ]);
 535
 536                   'bin' has the intended executable file name
 537                   *without* extension, obj2bin is expected to add
 538                   that.  'objs' has the list of object files to build
 539                   this library.  'deps' has the list of library files
 540                   (also *without* extension) that the programs needs
 541                   to be linked with.
 542
 543     in2script   - function that produces build file lines to build a
 544                   script file from some input.
 545
 546                   called like this:
 547
 548                         in2script(script => "PATH/TO/scriptfile",
 549                                   sources => [ "PATH/TO/infile", ... ]);
 550
 551                   'script' has the intended script file name.
 552                   'sources' has the list of source files to build the
 553                   resulting script from.
 554
 555 Along with the build-file templates is the driving template
 556 [`Configurations/common.tmpl`](common.tmpl), which looks through all the
 557 information in `%unified_info` and generates all the rulesets to build libraries,
 558 programs and all intermediate files, using the rule generating
 559 functions defined in the build-file template.
 560
 561 As an example with the smaller `build.info` set we've seen as an
 562 example, producing the rules to build `libcrypto` would result in the
 563 following calls:
 564
 565     # Note: obj2shlib will only be called if shared libraries are
 566     # to be produced.
 567     # Note 2: obj2shlib must convert the '.o' extension to whatever
 568     # is suitable on the local platform.
 569     obj2shlib(shlib => "libcrypto",
 570               objs => [ "crypto/aes.o", "crypto/evp.o", "crypto/cversion.o" ],
 571               deps => [  ]);
 572
 573     obj2lib(lib => "libcrypto"
 574             objs => [ "crypto/aes.o", "crypto/evp.o", "crypto/cversion.o" ]);
 575
 576     src2obj(obj => "crypto/aes.o"
 577             srcs => [ "crypto/aes.c" ],
 578             deps => [ ],
 579             incs => [ "include" ],
 580             intent => "lib");
 581
 582     src2obj(obj => "crypto/evp.o"
 583             srcs => [ "crypto/evp.c" ],
 584             deps => [ ],
 585             incs => [ "include" ],
 586             intent => "lib");
 587
 588     src2obj(obj => "crypto/cversion.o"
 589             srcs => [ "crypto/cversion.c" ],
 590             deps => [ "crypto/buildinf.h" ],
 591             incs => [ "include" ],
 592             intent => "lib");
 593
 594     generatesrc(src => "crypto/buildinf.h",
 595                 generator => [ "util/mkbuildinf.pl", "\"$(CC)",
 596                                "$(CFLAGS)\"", "\"$(PLATFORM)\"" ],
 597                 generator_incs => [ "util" ],
 598                 generator_deps => [ "util/Foo.pm" ],
 599                 incs => [ ],
 600                 deps => [ ],
 601                 intent => "lib");
 602
 603 The returned strings from all those calls are then concatenated
 604 together and written to the resulting build-file.