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Here is the procedure for installing GNU CC on a Unix system.
| 1.1 Compilation in a Separate Directory | Compiling in a separate directory (not where the source is). | |
| 1.2 Building and Installing a Cross-Compiler | Building and installing a cross-compiler. | |
| 1.3 Installing on the HP Precision Architecture | See below for installation on the HP Precision Architecture. | |
| 1.4 Installing GNU CC on the Sun | See below for installation on the Sun. | |
| 1.5 Installing GNU CC on the 3b1 | See below for installation on the 3b1. | |
| 1.6 Installing GNU CC on Unos | See below for installation on Unos (from CRDS). | |
| 1.7 Installing GNU CC on VMS | See below for installation on VMS. | |
| 1.8 Installing GNU CC on the WE32K | See below for installation on the 3b* aside from the 3b1. | |
| 1.9 Installing GNU CC on the MIPS | See below for installation on the MIPS Architecture. | |
1.10 collect2 | How collect2 works; how it finds ld.
| |
| 1.11 Standard Header File Directories | Understanding the standard header file directories. |
You cannot install GNU C by itself on MSDOS; it will not compile under any MSDOS compiler except itself. You need to get the complete compilation package DJGPP, which includes binaries as well as sources, and includes all the necessary compilation tools and libraries.
PATH. The cc command in
‘/usr/ucb’ uses libraries which have bugs.
If you are building a compiler to produce code for the machine it runs on, specify just one machine type, with the ‘--target’ option; the host type will default to be the same as the target. (For information on building a cross-compiler, see Building and Installing a Cross-Compiler.) Here is an example:
configure --target=sparc-sun-sunos4.1
If you run ‘configure’ without specifying configuration arguments, ‘configure’ tries to guess the type of host you are on, and uses that configuration type for both host and target. So you don’t need to specify a configuration, for building a native compiler, unless ‘configure’ cannot figure out what your configuration is.
A configuration name may be canonical or it may be more or less abbreviated.
A canonical configuration name has three parts, separated by dashes. It looks like this: ‘cpu-company-system’. (The three parts may themselves contain dashes; ‘configure’ can figure out which dashes serve which purpose.) For example, ‘m68k-sun-sunos4.1’ specifies a Sun 3.
You can also replace parts of the configuration by nicknames or aliases. For example, ‘sun3’ stands for ‘m68k-sun’, so ‘sun3-sunos4.1’ is another way to specify a Sun 3. You can also use simply ‘sun3-sunos’, since the version of SunOS is assumed by default to be version 4. ‘sun3-bsd’ also works, since ‘configure’ knows that the only BSD variant on a Sun 3 is SunOS.
You can specify a version number after any of the system types, and some of the CPU types. In most cases, the version is irrelevant, and will be ignored. So you might as well specify the version if you know it.
Here are the possible CPU types:
a29k, alpha, arm, cn, clipper, elxsi, h8300, hppa1.0, hppa1.1, i370, i386, i486, i860, i960, m68000, m68k, m88k, mips, ns32k, pyramid, romp, rs6000, sh, sparc, sparclite, vax, we32k.
Here are the recognized company names. As you can see, customary abbreviations are used rather than the longer official names.
alliant, altos, apollo, att, bull, cbm, convergent, convex, crds, dec, dg, dolphin, elxsi, encore, harris, hitachi, hp, ibm, intergraph, isi, mips, motorola, ncr, next, ns, omron, plexus, sequent, sgi, sony, sun, tti, unicom.
The company name is meaningful only to disambiguate when the rest of the information supplied is insufficient. You can omit it, writing just ‘cpu-system’, if it is not needed. For example, ‘vax-ultrix4.2’ is equivalent to ‘vax-dec-ultrix4.2’.
Here is a list of system types:
aix, acis, aos, bsd, clix, ctix, dgux, dynix, genix, hpux, isc, linux, luna, lynxos, mach, minix, newsos, osf, osfrose, riscos, sco, solaris, sunos, sysv, ultrix, unos, vms.
You can omit the system type; then ‘configure’ guesses the operating system from the CPU and company.
You can add a version number to the system type; this may or may not make a difference. For example, you can write ‘bsd4.3’ or ‘bsd4.4’ to distinguish versions of BSD. In practice, the version number is most needed for ‘sysv3’ and ‘sysv4’, which are often treated differently.
If you specify an impossible combination such as ‘i860-dg-vms’, then you may get an error message from ‘configure’, or it may ignore part of the information and do the best it can with the rest. ‘configure’ always prints the canonical name for the alternative that it used.
Often a particular model of machine has a name. Many machine names are recognized as aliases for CPU/company combinations. Thus, the machine name ‘sun3’, mentioned above, is an alias for ‘m68k-sun’. Sometimes we accept a company name as a machine name, when the name is popularly used for a particular machine. Here is a table of the known machine names:
3300, 3b1, 3bn, 7300, altos3068, altos, apollo68, att-7300, balance, convex-cn, crds, decstation-3100, decstation, delta, encore, fx2800, gmicro, hp7nn, hp8nn, hp9k2nn, hp9k3nn, hp9k7nn, hp9k8nn, iris4d, iris, isi68, m3230, magnum, merlin, miniframe, mmax, news-3600, news800, news, next, pbd, pc532, pmax, ps2, risc-news, rtpc, sun2, sun386i, sun386, sun3, sun4, symmetry, tower-32, tower.
Remember that a machine name specifies both the cpu type and the company name.
There are four additional options you can specify independently to describe variant hardware and software configurations. These are ‘--with-gnu-as’, ‘--with-gnu-ld’, ‘--with-stabs’ and ‘--nfp’.
If you will use GNU CC with the GNU assembler (GAS), you should declare this by using the ‘--with-gnu-as’ option when you run ‘configure’.
Using this option does not install GAS. It only modifies the output of GNU CC to work with GAS. Building and installing GAS is up to you.
Conversely, if you do not wish to use GAS and do not specify
‘--with-gnu-as’ when building GNU CC, it is up to you to make sure
that GAS is not installed. GNU CC searches for a program named
as in various directories; if the program it finds is GAS, then
it runs GAS. If you are not sure where GNU CC finds the assembler it is
using, try specifying ‘-v’ when you run it.
The systems where it makes a difference whether you use GAS are
‘hppa1.0-any-any’, ‘hppa1.1-any-any’,
‘i386-any-sysv’, ‘i386-any-isc’,
‘i860-any-bsd’, ‘m68k-bull-sysv’, ‘m68k-hp-hpux’,
‘m68k-sony-bsd’,
‘m68k-altos-sysv’, ‘m68000-hp-hpux’, ‘m68000-att-sysv’,
and ‘mips-any’). On any other system, ‘--with-gnu-as’
has no effect.
On the systems listed above (except for the HP-PA and for ISC on the 386), if you use GAS, you should also use the GNU linker (and specify ‘--with-gnu-ld’).
Specify the option ‘--with-gnu-ld’ if you plan to use the GNU linker with GNU CC.
This option does not cause the GNU linker to be installed; it just
modifies the behavior of GNU CC to work with the GNU linker.
Specifically, it inhibits the installation of collect2, a program
which otherwise serves as a front-end for the system’s linker on most
configurations.
On MIPS based systems and on Alphas, you must specify whether you want GNU CC to create the normal ECOFF debugging format, or to use BSD-style stabs passed through the ECOFF symbol table. The normal ECOFF debug format cannot fully handle languages other than C. BSD stabs format can handle other languages, but it only works with the GNU debugger GDB.
Normally, GNU CC uses the ECOFF debugging format by default; if you prefer BSD stabs, specify ‘--with-stabs’ when you configure GNU CC.
No matter which default you choose when you configure GNU CC, the user can use the ‘-gcoff’ and ‘-gstabs+’ options to specify explicitly the debug format for a particular compilation.
‘--with-stabs’ is meaningful on the ISC system on the 386, also, if ‘--with-gas’ is used. It selects use of stabs debugging information embedded in COFF output. This kind of debugging information supports C++ well; ordinary COFF debugging information does not.
On certain systems, you must specify whether the machine has a floating point unit. These systems include ‘m68k-sun-sunosn’ and ‘m68k-isi-bsd’. On any other system, ‘--nfp’ currently has no effect, though perhaps there are other systems where it could usefully make a difference.
If you want to install your own homemade configuration files, you can use ‘local’ as the company name to access them. If you use configuration ‘cpu-local’, the configuration name without the cpu prefix is used to form the configuration file names.
Thus, if you specify ‘m68k-local’, configuration uses files ‘local.md’, ‘local.h’, ‘local.c’, ‘xm-local.h’, ‘t-local’, and ‘x-local’, all in the directory ‘config/m68k’.
Here is a list of configurations that have special treatment or special things you must know:
Systems using processors that implement the DEC Alpha architecture and are running the OSF/1 operating system, for example the DEC Alpha AXP systems. (VMS on the Alpha is not currently supported by GNU CC.)
Objective C and C++ do not yet work on the Alpha. We hope to support C++ in version 2.6.
GNU CC writes a ‘.verstamp’ directive to the assembler output file unless it is built as a cross-compiler. It gets the version to use from the system header file ‘/usr/include/stamp.h’. If you install a new version of OSF/1, you should rebuild GCC to pick up the new version stamp.
Note that since the Alpha is a 64-bit architecture, cross-compilers from 32-bit machines will not generate as efficient code as that generated when the compiler is running on a 64-bit machine because many optimizations that depend on being able to represent a word on the target in an integral value on the host cannot be performed. Building cross-compilers on the Alpha for 32-bit machines has only been tested in a few cases and may not work properly.
make compare may fail on some versions of OSF/1 unless you add
‘-save-temps’ to CFLAGS. The same problem occurs on Irix
version 5.1.1. On these systems, the name of the assembler input file
is stored in the object file, and that makes comparison fail if it
differs between the stage1 and stage2 compilations. The
option ‘-save-temps’ forces a fixed name to be used for the
assembler input file, instead of a randomly chosen name in ‘/tmp’.
GNU CC now supports both the native (ECOFF) debugging format used by DBX and GDB and an encapsulated STABS format for use only with GDB. See the discussion of the ‘--with-stabs’ option of ‘configure’ above for more information on these formats and how to select them.
There is a bug in DEC’s assembler that produces incorrect line numbers for ECOFF format when the ‘.align’ directive is used. To work around this problem, GNU CC will not emit such alignment directives even if optimization is being performed if it is writing ECOFF format debugging information. Unfortunately, this has the very undesirable side-effect that code addresses when ‘-O’ is specified are different depending on whether or not ‘-g’ is also specified.
To avoid this behavior, specify ‘-gstabs+’ and use GDB instead of DBX. DEC is now aware of this problem with the assembler and hopes to provide a fix shortly.
AMD Am29k-family processors. These are normally used in embedded applications. There are no standard Unix configurations. This configuration corresponds to AMD’s standard calling sequence and binary interface and is compatible with other 29k tools.
You may need to make a variant of the file ‘a29k.h’ for your particular configuration.
AMD Am29050 used in a system running a variant of BSD Unix.
The Elxsi’s C compiler has known limitations that prevent it from
compiling GNU C. Please contact mrs@cygnus.com for more details.
Using GAS is highly recommended for all HP-PA configurations. See Installing on the HP Precision Architecture for the special procedures needed to compile GNU CC for the HP-PA.
Compilation with RCC is recommended. Also, it may be a good idea to link with GNU malloc instead of the malloc that comes with the system.
Use this configuration for SCO release 3.2 version 4.
It may be good idea to link with GNU malloc instead of the malloc that comes with the system.
It may be good idea to link with GNU malloc instead of the malloc that comes with the system.
You need to use GAS version 2.1 or later, and and LD from GNU binutils version 2.2 or later.
Go to the Berkeley universe before compiling. In addition, you probably need to create a file named ‘string.h’ containing just one line: ‘#include <strings.h>’.
You may find that you need another version of GNU CC to begin bootstrapping with, since the current version when built with the system’s own compiler seems to get an infinite loop compiling part of ‘libgcc2.c’. GNU CC version 2 compiled with GNU CC (any version) seems not to have this problem.
This is the Paragon. If you have version 1.0 of the operating system, see @ref{Installation Problems}, for special things you need to do to compensate for peculiarities in the system.
AT&T 3b1, a.k.a. 7300 PC. Special procedures are needed to compile GNU CC with this machine’s standard C compiler, due to bugs in that compiler. See section Installing GNU CC on the 3b1. You can bootstrap it more easily with previous versions of GNU CC if you have them.
HP 9000 series 200 running BSD. Note that the C compiler that comes
with this system cannot compile GNU CC; contact law@cs.utah.edu
to get binaries of GNU CC for bootstrapping.
Altos 3068. You must use the GNU assembler, linker and debugger. Also, you must fix a kernel bug. Details in the file ‘README.ALTOS’.
Bull DPX/2 series 200 and 300 with BOS-2.00.45 up to BOS-2.01. GNU CC works
either with native assembler or GNU assembler. You can use
GNU assembler with native coff generation by providing ‘--gas’ to
the configure script or use GNU assembler with dbx-in-coff encapsulation
by providing ‘--gas --stabs’. For any problem with native
assembler or for availability of the DPX/2 port of GAS, contact
F.Pierresteguy@frcl.bull.fr.
HP 9000 series 300 or 400 running HP-UX. HP-UX version 8.0 has a bug in the assembler that prevents compilation of GNU CC. To fix it, get patch PHCO_0800 from HP.
In addition, ‘--gas’ does not currently work with this configuration. Changes in HP-UX have broken the library conversion tool and the linker.
Sun 3. We do not provide a configuration file to use the Sun FPA by default, because programs that establish signal handlers for floating point traps inherently cannot work with the FPA.
Motorola m88k running the AT&T/Unisoft/Motorola V.3 reference port. These systems tend to use the Green Hills C, revision 1.8.5, as the standard C compiler. There are apparently bugs in this compiler that result in object files differences between stage 2 and stage 3. If this happens, make the stage 4 compiler and compare it to the stage 3 compiler. If the stage 3 and stage 4 object files are identical, this suggests you encountered a problem with the standard C compiler; the stage 3 and 4 compilers may be usable.
It is best, however, to use an older version of GNU CC for bootstrapping if you have one.
Motorola m88k running DG/UX. To build native or cross compilers on DG/UX, you must first change to the 88open BCS software development environment. This is done by issuing this command:
eval `sde-target m88kbcs`
Tektronix XD88 running UTekV 3.2e. Do not turn on optimization while building stage1 if you bootstrap with the buggy Green Hills compiler. Also, The bundled LAI System V NFS is buggy so if you build in an NFS mounted directory, start from a fresh reboot, or avoid NFS all together. Otherwise you may have trouble getting clean comparisons between stages.
MIPS machines running the MIPS operating system in BSD mode. It’s
possible that some old versions of the system lack the functions
memcpy, memcmp, and memset. If your system lacks
these, you must remove or undo the definition of
TARGET_MEM_FUNCTIONS in ‘mips-bsd.h’.
Silicon Graphics MIPS machines running IRIX. In order to compile GCC on an SGI the "c.hdr.lib" option must be installed from the CD-ROM supplied from Silicon Graphics. This is found on the 2nd CD in release 4.0.1.
Sony MIPS NEWS. This works in NEWSOS 5.0.1, but not in 5.0.2 (which uses ELF instead of COFF). Support for 5.0.2 will probably be provided soon by volunteers. In particular, the linker does not like the code generated by GCC when shared libraries are linked in.
Encore ns32000 system. Encore systems are supported only under BSD.
National Semiconductor ns32000 system. Genix has bugs in alloca
and malloc; you must get the compiled versions of these from GNU
Emacs.
Go to the Berkeley universe before compiling. In addition, you probably need to create a file named ‘string.h’ containing just one line: ‘#include <strings.h>’.
UTEK ns32000 system (“merlin”). The C compiler that comes with this system cannot compile GNU CC; contact ‘tektronix!reed!mason’ to get binaries of GNU CC for bootstrapping.
The only operating systems supported for the IBM RT PC are AOS and
MACH. GNU CC does not support AIX running on the RT. We recommend you
compile GNU CC with an earlier version of itself; if you compile GNU CC
with hc, the Metaware compiler, it will work, but you will get
mismatches between the stage 2 and stage 3 compilers in various files.
These errors are minor differences in some floating-point constants and
can be safely ignored; the stage 3 compiler is correct.
Read the file ‘README.RS6000’ for information on how to get a fix for problems in the IBM assembler that interfere with GNU CC. You must either obtain the new assembler or avoid using the ‘-g’ switch. Note that ‘Makefile.in’ uses ‘-g’ by default when compiling ‘libgcc2.c’.
The PowerPC and POWER2 architectures are now supported, but have not been extensively tested due to lack of appropriate systems. Only AIX is supported on the PowerPC.
Objective C does not work on this architecture.
XLC version 1.3.0.0 will miscompile ‘jump.c’. XLC version 1.3.0.1 or later fixes this problem. We do not yet have a PTF number for this fix.
Don’t try compiling with Vax C (vcc). It produces incorrect code
in some cases (for example, when alloca is used).
Meanwhile, compiling ‘cp-parse.c’ with pcc does not work because of an internal table size limitation in that compiler. To avoid this problem, compile just the GNU C compiler first, and use it to recompile building all the languages that you want to run.
Here we spell out what files will be set up by configure. Normally
you need not be concerned with these files.
The top-level config file is located in the subdirectory ‘config’. Its name is always ‘xm-something.h’; usually ‘xm-machine.h’, but there are some exceptions.
If your system does not support symbolic links, you might want to set up ‘config.h’ to contain a ‘#include’ command which refers to the appropriate file.
Unless you have a convention other than ‘/gnu’ for site-specific files, it is a bad idea to specify ‘--local-prefix’.
Bison versions older than Sept 8, 1988 will produce incorrect output for ‘c-parse.c’.
Alternatively, you can do subsequent compilation using a value of the
PATH environment variable such that the necessary GNU tools come
before the standard system tools.
‘LANGUAGES=c’ specifies that only the C compiler should be compiled. The makefile normally builds compilers for all the supported languages; currently, C, C++ and Objective C. However, C is the only language that is sure to work when you build with other non-GNU C compilers. In addition, building anything but C at this stage is a waste of time.
In general, you can specify the languages to build by typing the argument ‘LANGUAGES="list"’, where list is one or more words from the list ‘c’, ‘c++’, and ‘objective-c’.
Ignore any warnings you may see about “statement not reached” in ‘insn-emit.c’; they are normal. Also, warnings about “unknown escape sequence” are normal in ‘genopinit.c’ and perhaps some other files. Any other compilation errors may represent bugs in the port to your machine or operating system, and should be investigated and reported (@pxref{Bugs}).
Some commercial compilers fail to compile GNU CC because they have bugs or limitations. For example, the Microsoft compiler is said to run out of macro space. Some Ultrix compilers run out of expression space; then you need to break up the statement where the problem happens.
If you are building with a previous GNU C compiler, do not use ‘CC=gcc’ on the make command or by editing the Makefile. Instead, use a full pathname to specify the compiler, such as ‘CC=/gnu/bin/gcc’. This is because make might execute the ‘gcc’ in the current directory before all of the compiler components have been built.
make stage1
The files are moved into a subdirectory named ‘stage1’.
Once installation is complete, you may wish to delete these files
with rm -r stage1.
Alternatively, you can do subsequent compilation using a value of the
PATH environment variable such that the necessary GNU tools come
before the standard system tools.
make CC="stage1/xgcc -Bstage1/" CFLAGS="-g -O"
This is called making the stage 2 compiler.
The command shown above builds compilers for all the supported
languages. If you don’t want them all, you can specify the languages to
build by typing the argument ‘LANGUAGES="list"’. list
should contain one or more words from the list ‘c’, ‘c++’,
‘objective-c’, and ‘proto’. Separate the words with spaces.
‘proto’ stands for the programs protoize and
unprotoize; they are not a separate language, but you use
LANGUAGES to enable or disable their installation.
If you are going to build the stage 3 compiler, then you might want to build only the C language in stage 2.
Once you have built the stage 2 compiler, if you are short of disk space, you can delete the subdirectory ‘stage1’.
On a 68000 or 68020 system lacking floating point hardware, unless you have selected a ‘tm.h’ file that expects by default that there is no such hardware, do this instead:
make CC="stage1/xgcc -Bstage1/" CFLAGS="-g -O -msoft-float"
make stage2 make CC="stage2/xgcc -Bstage2/" CFLAGS="-g -O"
This is called making the stage 3 compiler. Aside from the ‘-B’
option, the compiler options should be the same as when you made the
stage 2 compiler. But the LANGUAGES option need not be the
same. The command shown above builds compilers for all the supported
languages; if you don’t want them all, you can specify the languages to
build by typing the argument ‘LANGUAGES="list"’, as described
above.
Then compare the latest object files with the stage 2 object files—they ought to be identical, aside from time stamps (if any).
On some systems, meaningful comparison of object files is impossible; they always appear “different.” This is currently true on Solaris and probably on all systems that use ELF object file format. Some other systems where this is so are listed below.
Use this command to compare the files:
make compare
This will mention any object files that differ between stage 2 and stage 3. Any difference, no matter how innocuous, indicates that the stage 2 compiler has compiled GNU CC incorrectly, and is therefore a potentially serious bug which you should investigate and report (@pxref{Bugs}).
If your system does not put time stamps in the object files, then this is a faster way to compare them (using the Bourne shell):
for file in *.o; do cmp $file stage2/$file done
If you have built the compiler with the ‘-mno-mips-tfile’ option on MIPS machines, you will not be able to compare the files.
The Alpha stores file names of internal temporary files in the object files and ‘make compare’ does not know how to ignore them, so normally you cannot compare on the Alpha. However, if you use the ‘-save-temps’ option when compiling both stage 2 and stage 3, this causes the same file names to be used in both stages; then you can do the comparison.
make objc-runtime CC="stage2/xgcc -Bstage2/" CFLAGS="-g -O"
CC,
CFLAGS and LANGUAGES that you used when compiling the
files that are being installed. One reason this is necessary is that
some versions of Make have bugs and recompile files gratuitously when
you do this step. If you use the same variable values, those files will
be recompiled properly.
For example, if you have built the stage 2 compiler, you can use the following command:
make install CC="stage2/xgcc -Bstage2/" CFLAGS="-g -O" LANGUAGES="list"
This copies the files ‘cc1’, ‘cpp’ and ‘libgcc.a’ to files ‘cc1’, ‘cpp’ and ‘libgcc.a’ in the directory ‘/gnu/lib/gcc-lib/target/version’, which is where the compiler driver program looks for them. Here target is the target machine type specified when you ran ‘configure’, and version is the version number of GNU CC. This naming scheme permits various versions and/or cross-compilers to coexist.
This also copies the driver program ‘xgcc’ into ‘/gnu/bin/gcc’, so that it appears in typical execution search paths.
On some systems, this command causes recompilation of some files. This
is usually due to bugs in make. You should either ignore this
problem, or use GNU Make.
Warning: there is a bug in alloca in the Sun library. To
avoid this bug, be sure to install the executables of GNU CC that were
compiled by GNU CC. (That is, the executables from stage 2 or 3, not
stage 1.) They use alloca as a built-in function and never the
one in the library.
(It is usually better to install GNU CC executables from stage 2 or 3, since they usually run faster than the ones compiled with some other compiler.)
make install-libobjc CC="stage2/xgcc -Bstage2/" CFLAGS="-g -O"
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If you wish to build the object files and executables in a directory other than the one containing the source files, here is what you must do differently:
VPATH
feature. (GNU Make supports it, as do Make versions on most BSD
systems.)
make distclean
mkdir gcc-sun3 cd gcc-sun3
On systems that do not support symbolic links, this directory must be on the same file system as the source code directory.
../gcc/configure …
This also tells configure where to find the compiler sources;
configure takes the directory from the file name that was used to
invoke it. But if you want to be sure, you can specify the source
directory with the ‘--srcdir’ option, like this:
../gcc/configure --srcdir=../gcc sun3
The directory you specify with ‘--srcdir’ need not be the same
as the one that configure is found in.
Now, you can run make in that directory. You need not repeat the
configuration steps shown above, when ordinary source files change. You
must, however, run configure again when the configuration files
change, if your system does not support symbolic links.
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GNU CC can function as a cross-compiler for many machines, but not all.
Since GNU CC generates assembler code, you probably need a cross-assembler that GNU CC can run, in order to produce object files. If you want to link on other than the target machine, you need a cross-linker as well. You also need header files and libraries suitable for the target machine that you can install on the host machine.
| 1.2.1 Steps of Cross-Compilation | Using a cross-compiler involves several steps that may be carried out on different machines. | |
| 1.2.2 Configuring a Cross-Compiler | Configuring a cross-compiler. | |
| 1.2.3 Tools and Libraries for a Cross-Compiler | Where to put the linker and assembler, and the C library. | |
| 1.2.5 Cross-Compilers and Header Files | Finding and installing header files for a cross-compiler. | |
| 1.2.4 ‘libgcc.a’ and Cross-Compilers | Supplying arithmetic runtime routines (‘libgcc1.a’). | |
| 1.2.6 Actually Building the Cross-Compiler | Actually compiling the cross-compiler. |
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To compile and run a program using a cross-compiler involves several steps:
It is most convenient to do all of these steps on the same host machine, since then you can do it all with a single invocation of GNU CC. This requires a suitable cross-assembler and cross-linker. For some targets, the GNU assembler and linker are available.
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To build GNU CC as a cross-compiler, you start out by running
configure. You must specify two different configurations, the
host and the target. Use the ‘--host=host’ option for the
host and ‘--target=target’ to specify the target type. For
example, here is how to configure for a cross-compiler that runs on a
hypothetical Intel 386 system and produces code for an HP 68030 system
running BSD:
configure --target=m68k-hp-bsd4.3 --host=i386-bozotheclone-bsd4.3
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If you have a cross-assembler and cross-linker available, you should install them now. Put them in the directory ‘/gnu/target/bin’. Here is a table of the tools you should put in this directory:
This should be the cross-assembler.
This should be the cross-linker.
This should be the cross-archiver: a program which can manipulate archive files (linker libraries) in the target machine’s format.
This should be a program to construct a symbol table in an archive file.
The installation of GNU CC will find these programs in that directory, and copy or link them to the proper place to for the cross-compiler to find them when run later.
The easiest way to provide these files is to build the Binutils package and GAS. Configure them with the same ‘--host’ and ‘--target’ options that you use for configuring GNU CC, then build and install them. They install their executables automatically into the proper directory. Alas, they do not support all the targets that GNU CC supports.
If you want to install libraries to use with the cross-compiler, such as a standard C library, put them in the directory ‘/gnu/target/lib’; installation of GNU CC copies all all the files in that subdirectory into the proper place for GNU CC to find them and link with them. Here’s an example of copying some libraries from a target machine:
ftp target-machine lcd /gnu/target/lib cd /lib get libc.a cd /usr/lib get libg.a get libm.a quit
The precise set of libraries you’ll need, and their locations on the target machine, vary depending on its operating system.
Many targets require “start files” such as ‘crt0.o’ and
‘crtn.o’ which are linked into each executable; these too should be
placed in ‘/gnu/target/lib’. There may be several
alternatives for ‘crt0.o’, for use with profiling or other
compilation options. Check your target’s definition of
STARTFILE_SPEC to find out what start files it uses.
Here’s an example of copying these files from a target machine:
ftp target-machine lcd /gnu/target/lib prompt cd /lib mget *crt*.o cd /usr/lib mget *crt*.o quit
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Code compiled by GNU CC uses certain runtime support functions implicitly. Some of these functions can be compiled successfully with GNU CC itself, but a few cannot be. These problem functions are in the source file ‘libgcc1.c’; the library made from them is called ‘libgcc1.a’.
When you build a native compiler, these functions are compiled with some other compiler–the one that you use for bootstrapping GNU CC. Presumably it knows how to open code these operations, or else knows how to call the run-time emulation facilities that the machine comes with. But this approach doesn’t work for building a cross-compiler. The compiler that you use for building knows about the host system, not the target system.
So, when you build a cross-compiler you have to supply a suitable library ‘libgcc1.a’ that does the job it is expected to do.
To compile ‘libgcc1.c’ with the cross-compiler itself does not work. The functions in this file are supposed to implement arithmetic operations that GNU CC does not know how to open code, for your target machine. If these functions are compiled with GNU CC itself, they will compile into infinite recursion.
On any given target, most of these functions are not needed. If GNU CC can open code an arithmetic operation, it will not call these functions to perform the operation. It is possible that on your target machine, none of these functions is needed. If so, you can supply an empty library as ‘libgcc1.a’.
Many targets need library support only for multiplication and division.
If you are linking with a library that contains functions for
multiplication and division, you can tell GNU CC to call them directly
by defining the macros MULSI3_LIBCALL, and the like. These
macros need to be defined in the target description macro file. For
some targets, they are defined already. This may be sufficient to
avoid the need for libgcc1.a; if so, you can supply an empty library.
Some targets do not have floating point instructions; they need other functions in ‘libgcc1.a’, which do floating arithmetic. Recent versions of GNU CC have a file which emulates floating point. With a certain amount of work, you should be able to construct a floating point emulator that can be used as ‘libgcc1.a’. Perhaps future versions will contain code to do this automatically and conveniently. That depends on whether someone wants to implement it.
If your target system has another C compiler, you can configure GNU CC as a native compiler on that machine, build just ‘libgcc1.a’ with ‘make libgcc1.a’ on that machine, and use the resulting file with the cross-compiler. To do this, execute the following on the target machine:
cd target-build-dir configure --host=sparc --target=sun3 make libgcc1.a
And then this on the host machine:
ftp target-machine binary cd target-build-dir get libgcc1.a quit
Another way to provide the functions you need in ‘libgcc1.a’ is to
define the appropriate perform_… macros for those
functions. If these definitions do not use the C arithmetic operators
that they are meant to implement, you should be able to compile them
with the cross-compiler you are building. (If these definitions already
exist for your target file, then you are all set.)
To build ‘libgcc1.a’ using the perform macros, use
‘LIBGCC1=libgcc1.a OLDCC=./xgcc’ when building the compiler.
Otherwise, you should place your replacement library under the name
‘libgcc1.a’ in the directory in which you will build the
cross-compiler, before you run make.
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If you are cross-compiling a standalone program or a program for an embedded system, then you may not need any header files except the few that are part of GNU CC (and those of your program). However, if you intend to link your program with a standard C library such as ‘libc.a’, then you probably need to compile with the header files that go with the library you use.
The GNU C compiler does not come with these files, because (1) they are system-specific, and (2) they belong in a C library, not in a compiler.
If the GNU C library supports your target machine, then you can get the header files from there (assuming you actually use the GNU library when you link your program).
If your target machine comes with a C compiler, it probably comes with suitable header files also. If you make these files accessible from the host machine, the cross-compiler can use them also.
Otherwise, you’re on your own in finding header files to use when cross-compiling.
When you have found suitable header files, put them in ‘/gnu/target/include’, before building the cross compiler. Then installation will run fixincludes properly and install the corrected versions of the header files where the compiler will use them.
Provide the header files before you build the cross-compiler, because the build stage actually runs the cross-compiler to produce parts of ‘libgcc.a’. (These are the parts that can be compiled with GNU CC.) Some of them need suitable header files.
Here’s an example showing how to copy the header files from a target machine. On the target machine, do this:
(cd /usr/include; tar cf - .) > tarfile
Then, on the host machine, do this:
ftp target-machine lcd /gnu/target/include get tarfile quit tar xf tarfile
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Now you can proceed just as for compiling a single-machine compiler through the step of building stage 1. If you have not provided some sort of ‘libgcc1.a’, then compilation will give up at the point where it needs that file, printing a suitable error message. If you do provide ‘libgcc1.a’, then building the compiler will automatically compile and link a test program called ‘cross-test’; if you get errors in the linking, it means that not all of the necessary routines in ‘libgcc1.a’ are available.
If you are making a cross-compiler for an embedded system, and there is no ‘stdio.h’ header for it, then the compilation of ‘enquire’ will probably fail. The job of ‘enquire’ is to run on the target machine and figure out by experiment the nature of its floating point representation. ‘enquire’ records its findings in the header file ‘float.h’. If you can’t produce this file by running ‘enquire’ on the target machine, then you will need to come up with a suitable ‘float.h’ in some other way (or else, avoid using it in your programs).
Do not try to build stage 2 for a cross-compiler. It doesn’t work to rebuild GNU CC as a cross-compiler using the cross-compiler, because that would produce a program that runs on the target machine, not on the host. For example, if you compile a 386-to-68030 cross-compiler with itself, the result will not be right either for the 386 (because it was compiled into 68030 code) or for the 68030 (because it was configured for a 386 as the host). If you want to compile GNU CC into 68030 code, whether you compile it on a 68030 or with a cross-compiler on a 386, you must specify a 68030 as the host when you configure it.
To install the cross-compiler, use ‘make install’, as usual.
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There are two variants of this CPU, called 1.0 and 1.1, which have different machine descriptions. You must use the right one for your machine. All 7nn machines and 8n7 machines use 1.1, while all other 8nn machines use 1.0.
The easiest way to handle this problem is to use ‘configure hpnnn’ or ‘configure hpnnn-hpux’, where nnn is the model number of the machine. Then ‘configure’ will figure out if the machine is a 1.0 or 1.1. Use ‘uname -a’ to find out the model number of your machine.
‘-g’ does not work on HP-UX, since that system uses a peculiar
debugging format which GNU CC does not know about. There are preliminary
versions of GAS and GDB for the HP-PA which do work with GNU CC for
debugging. You can get them by anonymous ftp from jaguar.cs.utah.edu
‘dist’ subdirectory. You would need to install GAS in the file
/gnu/lib/gcc-lib/configuration/gccversion/as
where configuration is the configuration name (perhaps ‘hpnnn-hpux’) and gccversion is the GNU CC version number. Do this before starting the build process, otherwise you will get errors from the HPUX assembler while building ‘libgcc2.a’. The command
make install-dir
will create the necessary directory hierarchy so you can install GAS before building GCC.
If you obtained GAS before October 6, 1992 it is highly recommended you get a new one to avoid several bugs which have been discovered recently.
To enable debugging, configure GNU CC with the ‘--gas’ option before building.
It has been reported that GNU CC produces invalid assembly code for 1.1 machines running HP-UX 8.02 when using the HP assembler. Typically the errors look like this:
as: bug.s @line#15 [err#1060]
Argument 0 or 2 in FARG upper
- lookahead = ARGW1=FR,RTNVAL=GR
as: foo.s @line#28 [err#1060]
Argument 0 or 2 in FARG upper
- lookahead = ARGW1=FR
You can check the version of HP-UX you are running by executing the command ‘uname -r’. If you are indeed running HP-UX 8.02 on a PA and using the HP assembler then configure GCC with "hpnnn-hpux8.02".
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On Solaris (version 2.1), do not use the linker or other tools in
‘/usr/ucb’ to build GNU CC. Use /usr/ccs/bin.
Make sure the environment variable FLOAT_OPTION is not set when
you compile ‘libgcc.a’. If this option were set to f68881
when ‘libgcc.a’ is compiled, the resulting code would demand to be
linked with a special startup file and would not link properly without
special pains.
The GNU compiler does not really support the Super SPARC processor that is used in SPARC Station 10 and similar class machines. You can get code that runs by specifying ‘sparc’ as the cpu type; however, its performance is not very good, and may vary widely according to the compiler version and optimization options used. This is because the instruction scheduling parameters designed for the Sparc are not correct for the Super SPARC. Implementing scheduling parameters for the Super SPARC might be a good project for someone who is willing to learn a great deal about instruction scheduling in GNU CC.
There is a bug in alloca in certain versions of the Sun library.
To avoid this bug, install the binaries of GNU CC that were compiled by
GNU CC. They use alloca as a built-in function and never the one
in the library.
Some versions of the Sun compiler crash when compiling GNU CC. The problem is a segmentation fault in cpp. This problem seems to be due to the bulk of data in the environment variables. You may be able to avoid it by using the following command to compile GNU CC with Sun CC:
make CC="TERMCAP=x OBJS=x LIBFUNCS=x STAGESTUFF=x cc"
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Installing GNU CC on the 3b1 is difficult if you do not already have GNU CC running, due to bugs in the installed C compiler. However, the following procedure might work. We are unable to test it.
obstack_free in the file
‘tree.c’ with _obstack_free.
make to get the first-stage GNU CC.
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Use ‘configure unos’ for building on Unos.
The Unos assembler is named casm instead of as. For some
strange reason linking ‘/bin/as’ to ‘/bin/casm’ changes the
behavior, and does not work. So, when installing GNU CC, you should
install the following script as ‘as’ in the subdirectory where
the passes of GCC are installed:
#!/bin/sh casm $*
The default Unos library is named ‘libunos.a’ instead of ‘libc.a’. To allow GNU CC to function, either change all references to ‘-lc’ in ‘gcc.c’ to ‘-lunos’ or link ‘/lib/libc.a’ to ‘/lib/libunos.a’.
When compiling GNU CC with the standard compiler, to overcome bugs in
the support of alloca, do not use ‘-O’ when making stage 2.
Then use the stage 2 compiler with ‘-O’ to make the stage 3
compiler. This compiler will have the same characteristics as the usual
stage 2 compiler on other systems. Use it to make a stage 4 compiler
and compare that with stage 3 to verify proper compilation.
(Perhaps simply defining ALLOCA in ‘x-crds’ as described in
the comments there will make the above paragraph superfluous. Please
inform us of whether this works.)
Unos uses memory segmentation instead of demand paging, so you will need a lot of memory. 5 Mb is barely enough if no other tasks are running. If linking ‘cc1’ fails, try putting the object files into a library and linking from that library.
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The VMS version of GNU CC is distributed in a backup saveset containing both source code and precompiled binaries.
To install the ‘gcc’ command so you can use the compiler easily, in the same manner as you use the VMS C compiler, you must install the VMS CLD file for GNU CC as follows:
$ assign /system /translation=concealed - disk:[gcc.] gnu_cc $ assign /system /translation=concealed - disk:[gcc.include.] gnu_cc_include
with the appropriate disk and directory names. These commands can be placed in your system startup file so they will be executed whenever the machine is rebooted. You may, if you choose, do this via the ‘GCC_INSTALL.COM’ script in the ‘[GCC]’ directory.
$ set command /table=sys$common:[syslib]dcltables - /output=sys$common:[syslib]dcltables gnu_cc:[000000]gcc $ install replace sys$common:[syslib]dcltables
$ library/help sys$library:helplib.hlb gcc.hlp
Now you can invoke the compiler with a command like ‘gcc /verbose file.c’, which is equivalent to the command ‘gcc -v -c file.c’ in Unix.
If you wish to use GNU C++ you must first install GNU CC, and then perform the following steps:
$ assign /system /translation=concealed - disk:[gcc.gxx_include.] gnu_gxx_include
with the appropriate disk and directory name. If you are going to be using libg++, this is where the libg++ install procedure will install the libg++ header files.
The GNU C++ compiler can be invoked with a command like ‘gcc /plus /verbose file.cc’, which is equivalent to the command ‘g++ -v -c file.cc’ in Unix.
We try to put corresponding binaries and sources on the VMS distribution tape. But sometimes the binaries will be from an older version than the sources, because we don’t always have time to update them. (Use the ‘/version’ option to determine the version number of the binaries and compare it with the source file ‘version.c’ to tell whether this is so.) In this case, you should use the binaries you get to recompile the sources. If you must recompile, here is how:
$ @vmsconfig.com
$ assign /system /translation=concealed - disk:[bison.] gnu_bison
You may, if you choose, use the ‘INSTALL_BISON.COM’ script in the ‘[BISON]’ directory.
$ set command /table=sys$common:[syslib]dcltables - /output=sys$common:[syslib]dcltables - gnu_bison:[000000]bison $ install replace sys$common:[syslib]dcltables
To install the library, use the following commands:
$ library gnu_cc:[000000]gcclib/delete=(new,eprintf) $ library gnu_cc:[000000]gcclib/delete=L_* $ library libgcc2/extract=*/output=libgcc2.obj $ library gnu_cc:[000000]gcclib libgcc2.obj
The first command simply removes old modules that will be replaced with
modules from ‘libgcc2’ under different module names. The modules
new and eprintf may not actually be present in your
‘gcclib.olb’—if the VMS librarian complains about those modules
not being present, simply ignore the message and continue on with the
next command. The second command removes the modules that came from the
previous version of the library ‘libgcc2.c’.
Whenever you update the compiler on your system, you should also update the library with the above procedure.
$ assign dua0:[gcc.build_dir.]/translation=concealed, -
dua1:[gcc.source_dir.]/translation=concealed gcc_build
$ set default gcc_build:[000000]
where the directory ‘dua1:[gcc.source_dir]’ contains the source code, and the directory ‘dua0:[gcc.build_dir]’ is meant to contain all of the generated object files and executables. Once you have done this, you can proceed building GCC as described above. (Keep in mind that ‘gcc_build’ is a rooted logical name, and thus the device names in each element of the search list must be an actual physical device name rather than another rooted logical name).
extern const variables will not have
the read-only bit set, and the linker will generate warning messages
about mismatched psect attributes for these variables. These warning
messages are merely a nuisance, and can safely be ignored.
If you are compiling with a version of GNU CC older than 1.33, specify
‘/DEFINE=("inline=")’ as an option in all the compilations. This
requires editing all the gcc commands in ‘make-cc1.com’.
(The older versions had problems supporting inline.) Once you
have a working 1.33 or newer GNU CC, you can change this file back.
CC, CFLAGS, and
LIBS. See comments in those files. However, you must
also have a working version of the GNU assembler (GNU as, aka GAS) as
it is used as the back-end for GNU CC to produce binary object modules
and is not included in the GNU CC sources. GAS is also needed to
compile ‘libgcc2’ in order to build ‘gcclib’ (see above);
‘make-l2.com’ expects to be able to find it operational in
‘gnu_cc:[000000]gnu-as.exe’.
To use GNU CC on VMS, you need the VMS driver programs ‘gcc.exe’, ‘gcc.com’, and ‘gcc.cld’. They are distributed with the VMS binaries (‘gcc-vms’) rather than the GNU CC sources. GAS is also included in ‘gcc-vms’, as is Bison.
Once you have successfully built GNU CC with VAX C, you should use the
resulting compiler to rebuild itself. Before doing this, be sure to
restore the CC, CFLAGS, and LIBS definitions in
‘make-cccp.com’ and ‘make-cc1.com’. The second generation
compiler will be able to take advantage of many optimizations that must
be suppressed when building with other compilers.
Under previous versions of GNU CC, the generated code would occasionally give strange results when linked with the sharable ‘VAXCRTL’ library. Now this should work.
Even with this version, however, GNU CC itself should not be linked with
the sharable ‘VAXCRTL’. The version of qsort in
‘VAXCRTL’ has a bug (known to be present in VMS versions V4.6
through V5.5) which causes the compiler to fail.
The executables are generated by ‘make-cc1.com’ and
‘make-cccp.com’ use the object library version of ‘VAXCRTL’ in
order to make use of the qsort routine in ‘gcclib.olb’. If
you wish to link the compiler executables with the shareable image
version of ‘VAXCRTL’, you should edit the file ‘tm.h’ (created
by ‘vmsconfig.com’) to define the macro QSORT_WORKAROUND.
QSORT_WORKAROUND is always defined when GNU CC is compiled with
VAX C, to avoid a problem in case ‘gcclib.olb’ is not yet
available.
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These computers are also known as the 3b2, 3b5, 3b20 and other similar names. (However, the 3b1 is actually a 68000; see Installing GNU CC on the 3b1.)
Don’t use ‘-g’ when compiling with the system’s compiler. The system’s linker seems to be unable to handle such a large program with debugging information.
The system’s compiler runs out of capacity when compiling ‘stmt.c’ in GNU CC. You can work around this by building ‘cpp’ in GNU CC first, then use that instead of the system’s preprocessor with the system’s C compiler to compile ‘stmt.c’. Here is how:
mv /lib/cpp /lib/cpp.att
cp cpp /lib/cpp.gnu
echo '/lib/cpp.gnu -traditional ${1+"$@"}' > /lib/cpp
chmod +x /lib/cpp
The system’s compiler produces bad code for some of the GNU CC optimization files. So you must build the stage 2 compiler without optimization. Then build a stage 3 compiler with optimization. That executable should work. Here are the necessary commands:
make LANGUAGES=c CC=stage1/xgcc CFLAGS="-Bstage1/ -g" make stage2 make CC=stage2/xgcc CFLAGS="-Bstage2/ -g -O"
You may need to raise the ULIMIT setting to build a C++ compiler, as the file ‘cc1plus’ is larger than one megabyte.
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See Installing GNU CC about whether to use either of the options ‘--with-stabs’ or ‘--with-gnu-as’.
The MIPS C compiler needs to be told to increase its table size
for switch statements with the ‘-Wf,-XNg1500’ option in
order to compile ‘cp-parse.c’. If you use the ‘-O2’
optimization option, you also need to use ‘-Olimit 3000’.
Both of these options are automatically generated in the
‘Makefile’ that the shell script ‘configure’ builds.
If you override the CC make variable and use the MIPS
compilers, you may need to add ‘-Wf,-XNg1500 -Olimit 3000’.
MIPS computers running RISC-OS can support four different personalities: default, BSD 4.3, System V.3, and System V.4 (older versions of RISC-OS don’t support V.4). To configure GCC for these platforms use the following configurations:
rev’Default configuration for RISC-OS, revision rev.
revbsd’BSD 4.3 configuration for RISC-OS, revision rev.
revsysv4’System V.4 configuration for RISC-OS, revision rev.
revsysv’System V.3 configuration for RISC-OS, revision rev.
The revision rev mentioned above is the revision of
RISC-OS to use. You must reconfigure GCC when going from a
RISC-OS revision 4 to RISC-OS revision 5. This has the effect of
avoiding a linker
bug (see @ref{Installation Problems} for more details).
DECstations can support three different personalities: Ultrix, DEC OSF/1, and OSF/rose. To configure GCC for these platforms use the following configurations:
Ultrix configuration.
Dec’s version of OSF/1.
Open Software Foundation reference port of OSF/1 which uses the OSF/rose object file format instead of ECOFF. Normally, you would not select this configuration.
On Irix version 4.0.5F, and perhaps on some other versions as well, there is an assembler bug that reorders instructions incorrectly. To work around it, specify the target configuration ‘mips-sgi-irix4loser’. This configuration inhibits assembler optimization.
You can turn off assembler optimization in a compiler configured with target ‘mips-sgi-irix4’ using the ‘-noasmopt’ option. This compiler option passes the option ‘-O0’ to the assembler, to inhibit reordering.
The ‘-noasmopt’ option can be useful for testing whether a problem is due to erroneous assembler reordering. Even if a problem does not go away with ‘-noasmopt’, it may still be due to assembler reordering—perhaps GNU CC itself was miscompiled as a result.
We know this is inconvenient, but it’s the best that can be done at the last minute.
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collect2Many target systems do not have support in the assembler and linker for
“constructors”—initialization functions to be called before the
official “start” of main. On such systems, GNU CC uses a
utility called collect2 to arrange to call these functions at
start time.
The program collect2 works by linking the program once and
looking through the linker output file for symbols with particular names
indicating they are constructor functions. If it finds any, it
creates a new temporary ‘.c’ file containing a table of them,
compiles it, and links the program a second time including that file.
The actual calls to the constructors are carried out by a subroutine
called __main, which is called (automatically) at the beginning
of the body of main (provided main was compiled with GNU
CC).
The program collect2 is installed as ld in the directory
where the passes of the compiler are installed. When collect2
needs to find the real ld, it tries the following file
names:
PATH.
PATH.
PATH.
“The compiler’s search directories” means all the directories where
gcc searches for passes of the compiler. This includes
directories that you specify with ‘-B’.
Cross-compilers search a little differently:
PATH.
PATH.
PATH.
collect2 does not search for ‘ld’ using the compiler’s
search directories, because if it did, it would find itself—not the
real ld—and this could lead to infinite recursion. However,
the directory where collect2 is installed might happen to be in
PATH. That could lead collect2 to invoke itself anyway.
when looking for ld.
To prevent this, collect2 explicitly avoids running ld
using the file name under which collect2 itself was invoked. In
fact, it remembers up to two such names—in case one copy of
collect2 finds another copy (or version) of collect2
installed as ld in a second place in the search path.
If two file names to avoid are not sufficient, you may still encounter
an infinite recursion of collect2 processes. When this happens.
check all the files installed as ‘ld’ in any of the directories
searched, and straighten out the situation.
(In a future version, we will probably change collect2 to avoid
any reinvocation of a file from which any parent collect2 was
run.)
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GCC_INCLUDE_DIR means the same thing for native and cross. It is
where GNU CC stores its private include files, and also where GNU CC
stores the fixed include files. A cross compiled GNU CC runs
fixincludes on the header files in ‘$(tooldir)/include’.
(If the cross compilation header files need to be fixed, they must be
installed before GNU CC is built. If the cross compilation header files
are already suitable for ANSI C and GNU CC, nothing special need be
done).
GPLUS_INCLUDE_DIR means the same thing for native and cross. It
is where g++ looks first for header files. libg++
installs only target independent header files in that directory.
LOCAL_INCLUDE_DIR is used only for a native compiler. It is
normally ‘/gnu/include’. GNU CC searches this directory so
that users can install header files in ‘/gnu/include’.
CROSS_INCLUDE_DIR is used only for a cross compiler. GNU CC
doesn’t install anything there.
TOOL_INCLUDE_DIR is used for both native and cross compilers. It
is the place for other packages to install header files that GNU CC will
use. For a cross-compiler, this is the equivalent of
‘/usr/include’. When you build a cross-compiler,
fixincludes processes any header files in this directory.
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