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4. Installing GNU CC

Note most of this information is out of date and superseded by the new GCC install manual `gcc/doc/install.texi'. It is provided for historical reference only.

4.1 Files Created by configure  Files created by running configure.
4.2 Configurations Supported by GNU CC  
4.3 Building and Installing a Cross-Compiler  Building and installing a cross-compiler.
4.4 Installing GNU CC on VMS  See below for installation on VMS.
4.5 collect2  How collect2 works; how it finds ld.
4.6 Standard Header File Directories  Understanding the standard header file directories.

Here is the procedure for installing GNU CC on a GNU or Unix system. See 4.4 Installing GNU CC on VMS, for VMS systems.

  1. If you have chosen a configuration for GNU CC which requires other GNU tools (such as GAS or the GNU linker) instead of the standard system tools, install the required tools in the build directory under the names `as', `ld' or whatever is appropriate. This will enable the compiler to find the proper tools for compilation of the program `enquire'.

    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.

  2. Specify the host, build and target machine configurations. You do this when you run the `configure' script.

    The build machine is the system which you are using, the host machine is the system where you want to run the resulting compiler (normally the build machine), and the target machine is the system for which you want the compiler to generate code.

    If you are building a compiler to produce code for the machine it runs on (a native compiler), you normally do not need to specify any operands to `configure'; it will try to guess the type of machine you are on and use that as the build, host and target machines. So you don't need to specify a configuration when building a native compiler unless `configure' cannot figure out what your configuration is or guesses wrong.

    In those cases, specify the build machine's configuration name with the `--host' option; the host and target will default to be the same as the host machine. (If you are building a cross-compiler, see 4.3 Building and Installing a Cross-Compiler.)

    Here is an example:

    ./configure --host=sparc-sun-sunos4.1

    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 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.

    See 4.2 Configurations Supported by GNU CC, for a list of supported configuration names and notes on many of the configurations. You should check the notes in that section before proceeding any further with the installation of GNU CC.

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4.1 Files Created by configure

Here we spell out what files will be set up by configure. Normally you need not be concerned with these files.

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4.2 Configurations Supported by GNU CC

Here are the possible CPU types:

1750a, a29k, alpha, arm, avr, cn, clipper, dsp16xx, elxsi, fr30, h8300, hppa1.0, hppa1.1, i370, i386, i486, i586, i686, i786, i860, i960, m32r, m68000, m68k, m6811, m6812, m88k, mcore, mips, mipsel, mips64, mips64el, mn10200, mn10300, ns32k, pdp11, powerpc, powerpcle, romp, rs6000, sh, sparc, sparclite, sparc64, v850, vax, we32k.

Here are the recognized company names. As you can see, customary abbreviations are used rather than the longer official names.

acorn, alliant, altos, apollo, apple, 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, wrs.

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:

386bsd, aix, acis, amigaos, aos, aout, aux, bosx, bsd, clix, coff, ctix, cxux, dgux, dynix, ebmon, ecoff, elf, esix, freebsd, hms, genix, gnu, linux, linux-gnu, hiux, hpux, iris, irix, isc, luna, lynxos, mach, minix, msdos, mvs, netbsd, newsos, nindy, ns, osf, osfrose, ptx, riscix, riscos, rtu, sco, sim, solaris, sunos, sym, sysv, udi, ultrix, unicos, uniplus, unos, vms, vsta, vxworks, winnt, xenix.

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.

`linux-gnu' is the canonical name for the GNU/Linux target; however GNU CC will also accept `linux'. The version of the kernel in use is not relevant on these systems. A suffix such as `libc1' or `aout' distinguishes major versions of the C library; all of the suffixed versions are obsolete.

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. GNU CC does not support all possible alternatives.

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, powerpc, powerpcle, 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. 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 `m68k.md', `local.h', `m68k.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:

See 4.4 Installing GNU CC on VMS, for details on how to install GNU CC on VMS.

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4.3 Building and Installing a Cross-Compiler

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.

4.3.1 Steps of Cross-Compilation  Using a cross-compiler involves several steps that may be carried out on different machines.
4.3.2 Configuring a Cross-Compiler  Configuring a cross-compiler.
4.3.3 Tools and Libraries for a Cross-Compiler  Where to put the linker and assembler, and the C library.
4.3.4 Cross-Compilers and Header Files  Finding and installing header files for a cross-compiler.
4.3.5 Actually Building the Cross-Compiler  Actually compiling the cross-compiler.

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4.3.1 Steps of Cross-Compilation

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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4.3.2 Configuring a Cross-Compiler

To build GNU CC as a cross-compiler, you start out by running `configure'. Use the `--target=target' to specify the target type. If `configure' was unable to correctly identify the system you are running on, also specify the `--build=build' option. For example, here is how to configure for a cross-compiler that produces code for an HP 68030 system running BSD on a system that `configure' can correctly identify:

./configure --target=m68k-hp-bsd4.3

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4.3.3 Tools and Libraries for a Cross-Compiler

If you have a cross-assembler and cross-linker available, you should install them now. Put them in the directory `/usr/local/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 `/usr/local/target/lib'; installation of GNU CC copies 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 /usr/local/target/lib
cd /lib
get libc.a
cd /usr/lib
get libg.a
get libm.a

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 `/usr/local/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 /usr/local/target/lib
cd /lib
mget *crt*.o
cd /usr/lib
mget *crt*.o

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4.3.4 Cross-Compilers and Header Files

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 the directory `/usr/local/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 /usr/local/target/include
get tarfile
tar xf tarfile

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4.3.5 Actually Building the Cross-Compiler

Now you can proceed just as for compiling a single-machine compiler through the step of building stage 1.

If your target is exotic, you may need to provide the header file `float.h'.One way to do this is to compile `enquire' and run it on your target machine. 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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4.4 Installing GNU CC on VMS

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:

  1. Define the VMS logical names `GNU_CC' and `GNU_CC_INCLUDE' to point to the directories where the GNU CC executables (`gcc-cpp.exe', `gcc-cc1.exe', etc.) and the C include files are kept respectively. This should be done with the commands:

    $ 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.

  2. Install the `GCC' command with the command line:

    $ set command /table=sys$common:[syslib]dcltables -
      /output=sys$common:[syslib]dcltables gnu_cc:[000000]gcc
    $ install replace sys$common:[syslib]dcltables

  3. To install the help file, do the following:

    $ 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:

  1. Define the VMS logical name `GNU_GXX_INCLUDE' to point to the directory where the preprocessor will search for the C++ header files. This can be done with the command:

    $ 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 a C++ runtime library, this is where its install procedure will install its header files.

  2. Obtain the file `gcc-cc1plus.exe', and place this in the same directory that `gcc-cc1.exe' is kept.

    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:

  1. Execute the command procedure `vmsconfig.com' to set up the files `tm.h', `config.h', `aux-output.c', and `md.', and to create files `tconfig.h' and `hconfig.h'. This procedure also creates several linker option files used by `make-cc1.com' and a data file used by `make-l2.com'.

    $ @vmsconfig.com

  2. Setup the logical names and command tables as defined above. In addition, define the VMS logical name `GNU_BISON' to point at the to the directories where the Bison executable is kept. This should be done with the command:

    $ assign /system /translation=concealed -
      disk:[bison.] gnu_bison

    You may, if you choose, use the `INSTALL_BISON.COM' script in the `[BISON]' directory.

  3. Install the `BISON' command with the command line:

    $ set command /table=sys$common:[syslib]dcltables -
      /output=sys$common:[syslib]dcltables -
    $ install replace sys$common:[syslib]dcltables

  4. Type `@make-gcc' to recompile everything (alternatively, submit the file `make-gcc.com' to a batch queue). If you wish to build the GNU C++ compiler as well as the GNU CC compiler, you must first edit `make-gcc.com' and follow the instructions that appear in the comments.

  5. In order to use GCC, you need a library of functions which GCC compiled code will call to perform certain tasks, and these functions are defined in the file `libgcc2.c'. To compile this you should use the command procedure `make-l2.com', which will generate the library `libgcc2.olb'. `libgcc2.olb' should be built using the compiler built from the same distribution that `libgcc2.c' came from, and `make-gcc.com' will automatically do all of this for you.

    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.

  6. You may wish to build GCC in such a way that no files are written to the directory where the source files reside. An example would be the when the source files are on a read-only disk. In these cases, execute the following DCL commands (substituting your actual path names):

    $ 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).

  7. If you are building GNU CC with a previous version of GNU CC, you also should check to see that you have the newest version of the assembler. In particular, GNU CC version 2 treats global constant variables slightly differently from GNU CC version 1, and GAS version 1.38.1 does not have the patches required to work with GCC version 2. If you use GAS 1.38.1, then 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.

  8. If you want to build GNU CC with the VAX C compiler, you will need to make minor changes in `make-cccp.com' and `make-cc1.com' to choose alternate definitions of 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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4.5 collect2

GNU CC uses a utility called collect2 on nearly all systems to arrange to call various initialization 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). Calling __main is necessary, even when compiling C code, to allow linking C and C++ object code together. (If you use `-nostdlib', you get an unresolved reference to __main, since it's defined in the standard GCC library. Include `-lgcc' at the end of your compiler command line to resolve this reference.)

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:

"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:

collect2 explicitly avoids running ld using the file name under which collect2 itself was invoked. In fact, it remembers up a list of 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.

collect2 searches for the utilities nm and strip using the same algorithm as above for ld.

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4.6 Standard Header File Directories

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 ISO C and GNU CC, nothing special need be done).

GPLUSPLUS_INCLUDE_DIR means the same thing for native and cross. It is where g++ looks first for header files. The C++ library installs only target independent header files in that directory.

LOCAL_INCLUDE_DIR is used only for a native compiler. It is normally `/usr/local/include'. GNU CC searches this directory so that users can install header files in `/usr/local/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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