Lines Matching +full:in +full:- +full:built
16 kbuild Makefiles exist in every subdirectory
29 architecture-specific information to the top Makefile.
34 any built-in or modular targets.
51 working on. In order to do this effectively, they need some overall
69 kbuild infrastructure. This chapter introduces the syntax used in the
80 ----------------
83 These lines define the files to be built, any special compilation
90 obj-y += foo.o
92 This tells kbuild that there is one object in that directory, named
93 foo.o. foo.o will be built from foo.c or foo.S.
95 If foo.o shall be built as a module, the variable obj-m is used.
100 obj-$(CONFIG_FOO) += foo.o
102 $(CONFIG_FOO) evaluates to either y (for built-in) or m (for module).
106 Built-in object goals - obj-y
107 -----------------------------
110 in the $(obj-y) lists. These lists depend on the kernel
113 Kbuild compiles all the $(obj-y) files. It then calls
114 ``$(AR) rcSTP`` to merge these files into one built-in.a file.
116 linked into vmlinux by scripts/link-vmlinux.sh
118 The order of files in $(obj-y) is significant. Duplicates in
120 built-in.a and succeeding instances will be ignored.
123 (module_init() / __initcall) will be called during boot in the
124 order they appear. So keep in mind that changing the link
125 order may e.g. change the order in which your SCSI
133 obj-$(CONFIG_ISDN_I4L) += isdn.o
134 obj-$(CONFIG_ISDN_PPP_BSDCOMP) += isdn_bsdcomp.o
136 Loadable module goals - obj-m
137 -----------------------------
139 $(obj-m) specifies object files which are built as loadable
142 A module may be built from one source file or several source
143 files. In the case of one source file, the kbuild makefile
144 simply adds the file to $(obj-m).
149 obj-$(CONFIG_ISDN_PPP_BSDCOMP) += isdn_bsdcomp.o
151 Note: In this example $(CONFIG_ISDN_PPP_BSDCOMP) evaluates to "m"
153 If a kernel module is built from several source files, you specify
154 that you want to build a module in the same way as above; however,
156 module from, so you have to tell it by setting a $(<module_name>-y)
162 obj-$(CONFIG_ISDN_I4L) += isdn.o
163 isdn-y := isdn_net_lib.o isdn_v110.o isdn_common.o
165 In this example, the module name will be isdn.o. Kbuild will
166 compile the objects listed in $(isdn-y) and then run
167 ``$(LD) -r`` on the list of these files to generate isdn.o.
169 Due to kbuild recognizing $(<module_name>-y) for composite objects,
176 obj-$(CONFIG_EXT2_FS) += ext2.o
177 ext2-y := balloc.o dir.o file.o ialloc.o inode.o ioctl.o \
179 ext2-$(CONFIG_EXT2_FS_XATTR) += xattr.o xattr_user.o \
182 In this example, xattr.o, xattr_user.o and xattr_trusted.o are only
189 parts and then link this into built-in.a, as you would expect.
191 Library file goals - lib-y
192 --------------------------
194 Objects listed with obj-* are used for modules, or
195 combined in a built-in.a for that specific directory.
197 be included in a library, lib.a.
198 All objects listed with lib-y are combined in a single
200 Objects that are listed in obj-y and additionally listed in
201 lib-y will not be included in the library, since they will
203 For consistency, objects listed in lib-m will be included in lib.a.
205 Note that the same kbuild makefile may list files to be built-in
207 may contain both a built-in.a and a lib.a file.
212 lib-y := delay.o
215 actually recognize that there is a lib.a being built, the directory
216 shall be listed in libs-y.
220 Use of lib-y is normally restricted to ``lib/`` and ``arch/*/lib``.
222 Descending down in directories
223 ------------------------------
225 A Makefile is only responsible for building objects in its own
226 directory. Files in subdirectories should be taken care of by
227 Makefiles in these subdirs. The build system will automatically
228 invoke make recursively in subdirectories, provided you let it know of
231 To do so, obj-y and obj-m are used.
232 ext2 lives in a separate directory, and the Makefile present in fs/
238 obj-$(CONFIG_EXT2_FS) += ext2/
240 If CONFIG_EXT2_FS is set to either "y" (built-in) or "m" (modular)
241 the corresponding obj- variable will be set, and kbuild will descend
242 down in the ext2 directory.
248 When Kbuild descends into the directory with "y", all built-in objects
249 from that directory are combined into the built-in.a, which will be
252 When Kbuild descends into the directory with "m", in contrast, nothing
253 from that directory will be linked into vmlinux. If the Makefile in
254 that directory specifies obj-y, those objects will be left orphan.
255 It is very likely a bug of the Makefile or of dependencies in Kconfig.
257 Kbuild also supports dedicated syntax, subdir-y and subdir-m, for
259 do not contain kernel-space objects at all. A typical usage is to let
265 subdir-$(CONFIG_GCC_PLUGINS) += gcc-plugins
266 subdir-$(CONFIG_MODVERSIONS) += genksyms
267 subdir-$(CONFIG_SECURITY_SELINUX) += selinux
269 Unlike obj-y/m, subdir-y/m does not need the trailing slash since this
276 Non-builtin vmlinux targets - extra-y
277 -------------------------------------
279 extra-y specifies targets which are needed for building vmlinux,
280 but not combined into built-in.a.
292 extra-y += vmlinux.lds
294 $(extra-y) should only contain targets needed for vmlinux.
296 Kbuild skips extra-y when vmlinux is apparently not a final goal.
299 If you intend to build targets unconditionally, always-y (explained
300 in the next section) is the correct syntax to use.
302 Always built goals - always-y
303 -----------------------------
305 always-y specifies targets which are literally always built when
311 offsets-file := include/generated/asm-offsets.h
312 always-y += $(offsets-file)
315 -----------------
317 ccflags-y, asflags-y and ldflags-y
318 These three flags apply only to the kbuild makefile in which they
325 ccflags-y specifies options for compiling with $(CC).
330 ccflags-y := -Os -D_LINUX -DBUILDING_ACPICA
331 ccflags-$(CONFIG_ACPI_DEBUG) += -DACPI_DEBUG_OUTPUT
337 asflags-y specifies assembler options.
342 asflags-y := -ansi
344 ldflags-y specifies options for linking with $(LD).
349 ldflags-y += -T $(src)/decompress_$(arch-y).lds
351 subdir-ccflags-y, subdir-asflags-y
352 The two flags listed above are similar to ccflags-y and asflags-y.
353 The difference is that the subdir- variants have effect for the kbuild
355 Options specified using subdir-* are added to the commandline before
356 the options specified using the non-subdir variants.
360 subdir-ccflags-y := -Werror
362 ccflags-remove-y, asflags-remove-y
368 ccflags-remove-$(CONFIG_MCOUNT) += -pg
371 CFLAGS_$@ and AFLAGS_$@ only apply to commands in current
374 $(CFLAGS_$@) specifies per-file options for $(CC). The $@
377 CFLAGS_$@ has the higher priority than ccflags-remove-y; CFLAGS_$@
378 can re-add compiler flags that were removed by ccflags-remove-y.
383 CFLAGS_aha152x.o = -DAHA152X_STAT -DAUTOCONF
387 $(AFLAGS_$@) is a similar feature for source files in assembly
390 AFLAGS_$@ has the higher priority than asflags-remove-y; AFLAGS_$@
391 can re-add assembler flags that were removed by asflags-remove-y.
396 AFLAGS_head.o := -DTEXT_OFFSET=$(TEXT_OFFSET)
397 AFLAGS_crunch-bits.o := -Wa,-mcpu=ep9312
398 AFLAGS_iwmmxt.o := -Wa,-mcpu=iwmmxt
401 -------------------
406 2) ``CONFIG_`` options used in all prerequisite files
407 3) Command-line used to compile target
410 be re-compiled.
413 ------------
418 Another example are the architecture-specific Makefiles which
422 Kbuild is not executing in the directory where the Makefile is
430 referring to files located in the src tree.
436 prerequisites not only in the object tree but also in the source tree).
442 $(CPP) -DCHIP=810 - < $< | ... $(src)/script_asm.pl
453 echoing information to user in a rule is often a good practice
454 but when execution ``make -s`` one does not expect to see any output
457 text following $(kecho) to stdout except if ``make -s`` is used.
471 quiet_cmd_<command> - what shall be echoed
472 cmd_<command> - the command to execute
490 ------------------------
498 Kbuild achieves this by a kind of meta-programming.
500 if_changed is the macro used for this purpose, in the following form::
508 Any target that utilizes if_changed must be listed in $(targets),
510 always be built.
512 If the target is already listed in the recognized syntax such as
513 obj-y/m, lib-y/m, extra-y/m, always-y/m, hostprogs, userprogs, Kbuild
518 used in conjunction with custom rules as defined in `Custom Rules`_.
530 It stores the executed command in a corresponding .cmd
531 file and multiple calls would result in overwrites and
536 -----------------------
538 The kernel may be built with several different versions of
544 as-option
545 as-option is used to check if $(CC) -- when used to compile
546 assembler (``*.S``) files -- supports the given option. An optional
552 cflags-y += $(call as-option,-Wa$(comma)-isa=$(isa-y),)
554 In the above example, cflags-y will be assigned the option
555 -Wa$(comma)-isa=$(isa-y) if it is supported by $(CC).
559 as-instr
560 as-instr checks if the assembler reports a specific instruction
562 C escapes are supported in the test instruction
563 Note: as-instr-option uses KBUILD_AFLAGS for assembler options
565 cc-option
566 cc-option is used to check if $(CC) supports a given option, and if
572 cflags-y += $(call cc-option,-march=pentium-mmx,-march=i586)
574 In the above example, cflags-y will be assigned the option
575 -march=pentium-mmx if supported by $(CC), otherwise -march=i586.
576 The second argument to cc-option is optional, and if omitted,
577 cflags-y will be assigned no value if first option is not supported.
578 Note: cc-option uses KBUILD_CFLAGS for $(CC) options
580 cc-option-yn
581 cc-option-yn is used to check if $(CC) supports a given option
587 biarch := $(call cc-option-yn, -m32)
588 aflags-$(biarch) += -a32
589 cflags-$(biarch) += -m32
591 In the above example, $(biarch) is set to y if $(CC) supports the -m32
592 option. When $(biarch) equals "y", the expanded variables $(aflags-y)
593 and $(cflags-y) will be assigned the values -a32 and -m32,
596 Note: cc-option-yn uses KBUILD_CFLAGS for $(CC) options
598 cc-disable-warning
599 cc-disable-warning checks if $(CC) supports a given warning and returns
601 because gcc 4.4 and later accept any unknown -Wno-* option and only
602 warn about it if there is another warning in the source file.
606 KBUILD_CFLAGS += $(call cc-disable-warning, unused-but-set-variable)
608 In the above example, -Wno-unused-but-set-variable will be added to
611 gcc-min-version
612 gcc-min-version tests if the value of $(CONFIG_GCC_VERSION) is greater than
617 cflags-$(call gcc-min-version, 70100) := -foo
619 In this example, cflags-y will be assigned the value -foo if $(CC) is gcc and
622 clang-min-version
623 clang-min-version tests if the value of $(CONFIG_CLANG_VERSION) is greater
628 cflags-$(call clang-min-version, 110000) := -foo
630 In this example, cflags-y will be assigned the value -foo if $(CC) is clang
633 cc-cross-prefix
634 cc-cross-prefix is used to check if there exists a $(CC) in path with
636 prefix$(CC) in the PATH is returned - and if no prefix$(CC) is found
639 Additional prefixes are separated by a single space in the
640 call of cc-cross-prefix.
643 to set CROSS_COMPILE to well-known values but may have several
655 CROSS_COMPILE := $(call cc-cross-prefix, m68k-linux-gnu-)
660 -----------------------
662 ld-option
663 ld-option is used to check if $(LD) supports the supplied option.
664 ld-option takes two options as arguments.
672 LDFLAGS_vmlinux += $(call ld-option, -X)
675 -----------------
700 Two steps are required in order to use a host executable.
706 This can be done in two ways. Either add the dependency in a rule,
707 or utilise the variable ``always-y``.
708 Both possibilities are described in the following.
711 -------------------
713 In some cases there is a need to compile and run a program on the
717 built on the build host.
723 Kbuild assumes in the above example that bin2hex is made from a single
724 c-source file named bin2hex.c located in the same directory as
728 -----------------------
733 $(<executable>-objs) lists all objects used to link the final
740 lxdialog-objs := checklist.o lxdialog.o
743 files. In the above example, checklist.c is compiled to checklist.o
747 Note: The syntax <executable>-y is not permitted for host-programs.
750 ---------------------------
752 kbuild offers support for host programs written in C++. This was
760 qconf-cxxobjs := qconf.o
762 In the example above the executable is composed of the C++ file
763 qconf.cc - identified by $(qconf-cxxobjs).
772 qconf-cxxobjs := qconf.o
773 qconf-objs := check.o
776 ----------------------------
778 Kbuild offers support for host programs written in Rust. However,
780 it may only be used in scenarios where Rust is required to be
786 target-rust := y
789 located in the same directory as the ``Makefile``. The crate may
793 ----------------------------------------------
797 the options specified in $(KBUILD_HOSTCFLAGS).
800 in that Makefile, use the variable HOST_EXTRACFLAGS.
805 HOST_EXTRACFLAGS += -I/usr/include/ncurses
813 HOSTCFLAGS_piggyback.o := -DKERNELBASE=$(KERNELBASE)
820 HOSTLDLIBS_qconf := -L$(QTDIR)/lib
823 ``-L$(QTDIR)/lib``.
825 When host programs are actually built
826 -------------------------------------
828 Kbuild will only build host-programs when they are referenced
831 This is possible in two ways:
833 (1) List the prerequisite explicitly in a custom rule.
838 hostprogs := gen-devlist
839 $(obj)/devlist.h: $(src)/pci.ids $(obj)/gen-devlist
840 ( cd $(obj); ./gen-devlist ) < $<
842 The target $(obj)/devlist.h will not be built before
843 $(obj)/gen-devlist is updated. Note that references to
844 the host programs in custom rules must be prefixed with $(obj).
846 (2) Use always-y
849 shall be built when a makefile is entered, the always-y
856 always-y := $(hostprogs)
860 hostprogs-always-y := lxdialog
862 This will tell kbuild to build lxdialog even if not referenced in
876 ------------------------
878 The following line tells kbuild that the program bpf-direct shall be
879 built for the target architecture.
883 userprogs := bpf-direct
885 Kbuild assumes in the above example that bpf-direct is made from a
886 single C source file named bpf-direct.c located in the same directory
890 ----------------------------
895 $(<executable>-objs) lists all objects used to link the final
901 userprogs := bpf-fancy
902 bpf-fancy-objs := bpf-fancy.o bpf-helper.o
905 files. In the above example, bpf-fancy.c is compiled to bpf-fancy.o
906 and bpf-helper.c is compiled to bpf-helper.o.
908 Finally, the two .o files are linked to the executable, bpf-fancy.
909 Note: The syntax <executable>-y is not permitted for userspace programs.
912 ---------------------------------------------------
916 the options specified in $(KBUILD_USERCFLAGS).
919 in that Makefile, use the variable userccflags.
924 userccflags += -I usr/include
931 bpf-helper-userccflags += -I user/include
938 bpfilter_umh-userldflags += -static
941 ``<executable>-userldlibs``. The ``userldlibs`` syntax specifies libraries
942 linked to all userspace programs created in the current Makefile.
944 When linking bpfilter_umh, it will be passed the extra option -static.
948 When userspace programs are actually built
949 ------------------------------------------
962 $(obj)/bpfilter_umh is built before $(obj)/bpfilter_umh_blob.o
964 (2) Use always-y
969 always-y := $(userprogs)
973 userprogs-always-y := binderfs_example
981 ``make clean`` deletes most generated files in the obj tree where the kernel
983 Kbuild knows targets listed in $(hostprogs), $(always-y), $(always-m),
984 $(always-), $(extra-y), $(extra-) and $(targets). They are all deleted
989 Additional files or directories can be specified in kbuild makefiles by use of
990 $(clean-files).
995 clean-files := crc32table.h
998 Kbuild will assume files to be in the same relative directory as the
1002 $(no-clean-files) variable.
1004 Usually kbuild descends down in subdirectories due to ``obj-* := dir/``,
1005 but in the architecture makefiles where the kbuild infrastructure
1011 subdir- := compressed
1013 The above assignment instructs kbuild to descend down in the
1016 Note 1: arch/$(SRCARCH)/Makefile cannot use ``subdir-``, because that file is
1017 included in the top level makefile. Instead, arch/$(SRCARCH)/Kbuild can use
1018 ``subdir-``.
1020 Note 2: All directories listed in core-y, libs-y, drivers-y and net-y will
1027 before starting to descend down in the individual directories.
1040 2) Store kernel version in include/linux/version.h
1044 - Additional prerequisites are specified in arch/$(SRCARCH)/Makefile
1046 4) Recursively descend down in all directories listed in
1047 init-* core* drivers-* net-* libs-* and build all targets.
1049 - The values of the above variables are expanded in arch/$(SRCARCH)/Makefile.
1053 The very first objects linked are listed in scripts/head-object-list.txt.
1055 6) Finally, the architecture-specific part does any required post processing
1058 - This includes building boot records
1059 - Preparing initrd images and the like
1062 ----------------------------------------------------
1073 KBUILD_LDFLAGS := -m elf_s390
1075 Note: ldflags-y can be used to further customise
1076 the flags used. See `Non-builtin vmlinux targets - extra-y`_.
1089 LDFLAGS_vmlinux := -e stext
1095 the flags specified in OBJCOPYFLAGS will be used.
1103 OBJCOPYFLAGS := -O binary
1109 In this example, the binary $(obj)/image is a binary version of
1115 Default value - see top level Makefile.
1122 KBUILD_AFLAGS += -m64 -mcpu=ultrasparc
1127 Default value - see top level Makefile.
1136 cflags-$(CONFIG_X86_32) := -march=i386
1137 cflags-$(CONFIG_X86_64) := -mcmodel=small
1138 KBUILD_CFLAGS += $(cflags-y)
1146 cflags-$(CONFIG_MPENTIUMII) += $(call cc-option,\
1147 -march=pentium2,-march=i686)
1149 # Disable unit-at-a-time mode ...
1150 KBUILD_CFLAGS += $(call cc-option,-fno-unit-at-a-time)
1160 Default value - see top level Makefile.
1166 Note that target specification file generation (for ``--target``)
1167 is handled in ``scripts/generate_rust_target.rs``.
1170 Assembler options specific for built-in
1178 $(KBUILD_AFLAGS_MODULE) is used to add arch-specific options that
1184 $(CC) options specific for built-in
1192 $(KBUILD_CFLAGS_MODULE) is used to add arch-specific options that
1198 $(RUSTC) options specific for built-in
1206 $(KBUILD_RUSTFLAGS_MODULE) is used to add arch-specific options that
1214 $(KBUILD_LDFLAGS_MODULE) is used to add arch-specific options
1220 The linker script with full path. Assigned by the top-level Makefile.
1223 All object files for vmlinux. They are linked to vmlinux in the same
1224 order as listed in KBUILD_VMLINUX_OBJS.
1226 The objects listed in scripts/head-object-list.txt are exceptions;
1235 --------------------------------
1244 --------------------------------
1247 built before starting to descend down in the subdirectories.
1256 In this example, the file target maketools will be processed
1257 before descending down in the subdirectories.
1259 See also chapter XXX-TODO that describes how kbuild supports
1263 -----------------------------------------
1267 corresponding arch-specific section for modules; the module-building
1268 machinery is all architecture-independent.
1270 core-y, libs-y, drivers-y
1271 $(libs-y) lists directories where a lib.a archive can be located.
1273 The rest list directories where a built-in.a object file can be
1276 Then the rest follows in this order:
1278 $(core-y), $(libs-y), $(drivers-y)
1281 and arch/$(SRCARCH)/Makefile only adds architecture-specific
1287 core-y += arch/sparc/
1289 libs-y += arch/sparc/prom/
1290 libs-y += arch/sparc/lib/
1292 drivers-$(CONFIG_PM) += arch/sparc/power/
1294 Architecture-specific boot images
1295 ---------------------------------
1298 it, wrap it in bootstrapping code, and copy the resulting files
1302 It is common to locate any additional processing in a boot/
1306 target specified in boot/. Therefore arch/$(SRCARCH)/Makefile shall
1307 call make manually to build a target in boot/.
1309 The recommended approach is to include shortcuts in
1321 make in a subdirectory.
1323 There are no rules for naming architecture-specific targets,
1331 echo '* bzImage - Compressed kernel image (arch/x86/boot/bzImage)'
1335 will be built. In the top level Makefile the first goal present
1339 In ``make help``, the default goal is highlighted with a ``*``.
1349 When ``make`` is executed without arguments, bzImage will be built.
1352 -----------------------------------------
1363 LDFLAGS_bootsect := -Ttext 0x0 -s --oformat binary
1364 LDFLAGS_setup := -Ttext 0x0 -s --oformat binary -e begtext
1370 In this example, there are two possible targets, requiring different
1372 LDFLAGS_$@ syntax - one for each potential target.
1385 resulting in the target file being recompiled for no
1389 Copy binary. Uses OBJCOPYFLAGS usually specified in
1400 $(obj)/vmlinux.bin.gz: $(vmlinux.bin.all-y) FORCE
1406 in an init section in the image. Platform code *must* copy the
1407 blob to non-init memory prior to calling unflatten_device_tree().
1409 To use this command, simply add ``*.dtb`` into obj-y or targets, or make
1417 targets += $(dtb-y)
1418 DTC_FLAGS ?= -p 1024
1421 ----------------------------
1423 When the vmlinux image is built, the linker script
1427 located in the same directory.
1429 kbuild knows .lds files and includes a rule ``*lds.S`` -> ``*lds``.
1434 extra-y := vmlinux.lds
1436 The assignment to extra-y is used to tell kbuild to build the
1444 KBUILD_CPPFLAGS : Set in top-level Makefile
1445 cppflags-y : May be set in the kbuild makefile
1446 CPPFLAGS_$(@F) : Target-specific flags.
1447 Note that the full filename is used in this
1450 The kbuild infrastructure for ``*lds`` files is used in several
1451 architecture-specific files.
1454 --------------------
1456 The directory include/asm-generic contains the header files
1460 to list the file in the Kbuild file.
1462 See `generic-y`_ for further info on syntax etc.
1464 Post-link pass
1465 --------------
1468 will be invoked for post-link objects (vmlinux and modules.ko)
1469 for architectures to run post-link passes on. Must also handle
1475 .tmp_vmlinux? targets to be called from link-vmlinux.sh.
1484 Many headers can be exported as-is but other headers require a
1485 minimal pre-processing before they are ready for user-space.
1487 The pre-processing does:
1489 - drop kernel-specific annotations
1490 - drop include of compiler.h
1491 - drop all sections that are kernel internal (guarded by ``ifdef __KERNEL__``)
1498 arch/<arch>/include/asm/ to list asm files coming from asm-generic.
1502 no-export-headers
1503 -----------------
1505 no-export-headers is essentially used by include/uapi/linux/Kbuild to
1509 generic-y
1510 ---------
1513 include/asm-generic then this is listed in the file
1519 generic-y += termios.h
1520 generic-y += rtc.h
1523 file is generated in the directory::
1529 of the set of exported headers in the directory::
1533 The generated wrapper will in both cases look like the following:
1537 #include <asm-generic/termios.h>
1539 generated-y
1540 -----------
1542 If an architecture generates other header files alongside generic-y
1543 wrappers, generated-y specifies them.
1545 This prevents them being treated as stale asm-generic wrappers and
1551 generated-y += syscalls_32.h
1553 mandatory-y
1554 -----------
1556 mandatory-y is essentially used by include/(uapi/)asm-generic/Kbuild
1559 This works like optional generic-y. If a mandatory header is missing
1560 in arch/$(SRCARCH)/include/(uapi/)/asm, Kbuild will automatically
1561 generate a wrapper of the asm-generic one.
1574 three-part version number, such as "2", "4", and "0". These three
1577 $(EXTRAVERSION) defines an even tinier sublevel for pre-patches
1578 or additional patches. It is usually some non-numeric string
1579 such as "-pre4", and is often blank.
1582 $(KERNELRELEASE) is a single string such as "2.4.0-pre4", suitable
1583 for constructing installation directory names or showing in
1598 This variable specifies the directory in arch/ to build.
1602 both 32-bit and 64-bit.
1604 For example, you can pass in ARCH=i386, ARCH=x86_64, or ARCH=x86.
1611 Use this for architecture-specific install targets.
1615 installation. This variable is not defined in the Makefile but
1616 may be passed in by the user if desired.
1626 default option --strip-debug will be used. Otherwise, the
1633 INSTALL_MOD_PATH, it isn't defined in the Makefile, but can be passed
1644 GNU Make supports elementary list-processing functions. The kernel
1649 immediate evaluation of the right-hand side and stores an actual string
1650 into the left-hand side. ``=`` is like a formula definition; it stores the
1651 right-hand side in an unevaluated form and then evaluates this form each
1652 time the left-hand side is used.
1660 - Original version made by Michael Elizabeth Chastain, <mailto:mec@shout.net>
1661 - Updates by Kai Germaschewski <kai@tp1.ruhr-uni-bochum.de>
1662 - Updates by Sam Ravnborg <sam@ravnborg.org>
1663 - Language QA by Jan Engelhardt <jengelh@gmx.de>
1668 - Generating offset header files.
1669 - Add more variables to chapters 7 or 9?