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- This is Info file cfg-paper.info, produced by Makeinfo-1.55 from the
- input file ./cfg-paper.texi.
-
- This document attempts to describe the general concepts behind
- configuration of the GNU Development Tools. It also discusses common
- usage.
-
- Copyright (C) 1991, 1992, 1994 Cygnus Support Permission is granted
- to make and distribute verbatim copies of this manual provided the
- copyright notice and this permission notice are preserved on all copies.
-
- Permission is granted to copy and distribute modified versions of
- this manual under the conditions for verbatim copying, provided that
- the entire resulting derived work is distributed under the terms of a
- permission notice identical to this one.
-
- Permission is granted to copy and distribute translations of this
- manual into another language, under the above conditions for modified
- versions, except that this permission notice may be stated in a
- translation approved by Cygnus Support.
-
- START-INFO-DIR-ENTRY
- * configuration: (cfg-paper). Some theory on configuring source.
- END-INFO-DIR-ENTRY
-
- File: cfg-paper.info, Node: Top, Next: Some Basic Terms, Prev: (dir), Up: (dir)
-
- This document attempts to describe the general concepts behind
- configuration of the GNU Development Tools. It also discusses common
- usage.
-
- * Menu:
-
- * Some Basic Terms:: Some Basic Terms
- * Specifics.:: Specifics
- * Building Development Environments:: Building Development Environments
- * A Walk Through:: A Walk Through
- * Final Notes:: Final Notes
- * Index:: Index
-
- -- The Detailed Node Listing --
-
- Some Basic Terms
-
- * Host Environments:: Host Environments
- * Configuration Time Options:: Configuration Time Options
-
- A Walk Through
-
- * Native Development Environments:: Native Development Environments
- * Emulation Environments:: Emulation Environments
- * Simple Cross Environments:: Simple Cross Environments
- * Crossing Into Targets:: Crossing Into Targets
- * Canadian Cross:: Canadian Cross
-
- Final Notes
-
- * Hacking Configurations:: Hacking Configurations
-
- File: cfg-paper.info, Node: Some Basic Terms, Next: Specifics., Prev: Top, Up: Top
-
- Some Basic Terms
- ****************
-
- There are a lot of terms that are frequently used when discussing
- development tools. Most of the common terms have been used for many
- different concepts such that their meanings have become ambiguous to the
- point of being confusing. Typically, we only guess at their meanings
- from context and we frequently guess wrong.
-
- This document uses very few terms by comparison. The intent is to
- make the concepts as clear as possible in order to convey the usage and
- intent of these tools.
-
- *Programs* run on *machines*. Programs are very nearly always
- written in *source*. Programs are *built* from source. *Compilation*
- is a process that is frequently, but not always, used when building
- programs.
-
- * Menu:
-
- * Host Environments:: Host Environments
- * Configuration Time Options:: Configuration Time Options
-
- File: cfg-paper.info, Node: Host Environments, Next: Configuration Time Options, Prev: Some Basic Terms, Up: Some Basic Terms
-
- Host Environments
- =================
-
- In this document, the word *host* refers to the environment in which
- the source in question will be compiled. *host* and *host name* have
- nothing to do with the proper name of your host, like *ucbvax*,
- *prep.ai.mit.edu* or *att.com*. Instead they refer to things like
- *sun4* and *dec3100*.
-
- Forget for a moment that this particular directory of source is the
- source for a development environment. Instead, pretend that it is the
- source for a simpler, more mundane, application, say, a desk calculator.
-
- Source that can be compiled in more than one environment, generally
- needs to be set up for each environment explicitly. Here we refer to
- that process as configuration. That is, we configure the source for a
- host.
-
- For example, if we wanted to configure our mythical desk calculator
- to compile on a SparcStation, we might configure for host sun4. With
- our configuration system:
-
- cd desk-calculator ; ./configure sun4
-
- does the trick. `configure' is a shell script that sets up Makefiles,
- subdirectories, and symbolic links appropriate for compiling the source
- on a sun4.
-
- The *host* environment does not necessarily refer to the machine on
- which the tools are built. It is possible to provide a sun3 development
- environment on a sun4. If we wanted to use a cross compiler on the sun4
- to build a program intended to be run on a sun3, we would configure the
- source for sun3.
-
- cd desk-calculator ; ./configure sun3
-
- The fact that we are actually building the program on a sun4 makes no
- difference if the sun3 cross compiler presents an environment that looks
- like a sun3 from the point of view of the desk calculator source code.
- Specifically, the environment is a sun3 environment if the header files,
- predefined symbols, and libraries appear as they do on a sun3.
-
- Nor does the host environment refer to the the machine on which the
- program to be built will run. It is possible to provide a sun3
- emulation environment on a sun4 such that programs built in a sun3
- development environment actually run on the sun4. This technique is
- often used within individual programs to remedy deficiencies in the host
- operating system. For example, some operating systems do not provide
- the `bcopy' function and so it is emulated using the `memcpy' funtion.
-
- Host environment simply refers to the environment in which the
- program will be built from the source.
-
- File: cfg-paper.info, Node: Configuration Time Options, Prev: Host Environments, Up: Some Basic Terms
-
- Configuration Time Options
- ==========================
-
- Many programs have compile time options. That is, features of the
- program that are either compiled into the program or not based on a
- choice made by the person who builds the program. We refer to these as
- *configuration options*. For example, our desk calculator might be
- capable of being compiled into a program that either uses infix notation
- or postfix as a configuration option. For a sun3, to choose infix you
- might use:
-
- ./configure sun3 --enable-notation=infix
-
- while for a sun4 with postfix you might use:
-
- ./configure sun4 --enable-notation=postfix
-
- If we wanted to build both at the same time, the intermediate pieces
- used in the build process must be kept separate.
-
- mkdir ../objdir.sun4
- (cd ../objdir.sun4 ; ../configure sun4 --enable-notation=postfix --srcdir=../src)
- mkdir ../objdir.sun3
- (cd ../objdir.sun3 ; ../configure sun3 --enable-notation=infix --srcdir=../src)
-
- will create subdirectories for the intermediate pieces of the sun4 and
- sun3 configurations. This is necessary as previous systems were only
- capable of one configuration at a time. Otherwise, a second
- configuration would write over the first. We've chosen to retain this
- behaviour so the obj directories and the `--srcdir' configuration
- option are necessary to get the new behaviour. The order of the
- arguments doesn't matter. There should be exactly one argument without
- a leading `-' and that argument will be assumed to be the host name.
-
- From here on the examples will assume that you want to build the
- tools *in place* and won't show the `--srcdir' option, but remember
- that it is available.
-
- In order to actually install the program, the configuration system
- needs to know where you would like the program installed. The default
- location is `/usr/local'. We refer to this location as `$(prefix)'.
- All user visible programs will be installed in ``$(prefix)'/bin'. All
- other programs and files will be installed in a subdirectory of
- ``$(prefix)'/lib'.
-
- You can only change `$(prefix)' as a configuration time option.
-
- ./configure sun4 --enable-notation=postfix --prefix=/local
-
- Will configure the source such that:
-
- make install
-
- will put its programs in `/local/bin' and `/local/lib/gcc'. If you
- change `$(prefix)' after building the source, you will need to:
-
- make clean
-
- before the change will be propogated properly. This is because some
- tools need to know the locations of other tools.
-
- With these concepts in mind, we can drop the desk calculator example
- and move on to the application that resides in these directories,
- namely, the source to a development environment.
-
- File: cfg-paper.info, Node: Specifics., Next: Building Development Environments, Prev: Some Basic Terms, Up: Top
-
- Specifics
- *********
-
- The GNU Development Tools can be built on a wide variety of hosts.
- So, of course, they must be configured. Like the last example,
-
- ./configure sun4 --prefix=/local
- ./configure sun3 --prefix=/local
-
- will configure the source to be built in subdirectories, in order to
- keep the intermediate pieces separate, and to be installed in `/local'.
-
- When built with suitable development environments, these will be
- native tools. We'll explain the term *native* later.
-
- File: cfg-paper.info, Node: Building Development Environments, Next: A Walk Through, Prev: Specifics., Up: Top
-
- Building Development Environments
- *********************************
-
- The GNU development tools can not only be built in a number of host
- development environments, they can also be configured to create a
- number of different development environments on each of those hosts.
- We refer to a specific development environment created as a *target*.
- That is, the word *target* refers to the development environment
- produced by compiling this source and installing the resulting programs.
-
- For the GNU development tools, the default target is the same as the
- host. That is, the development environment produced is intended to be
- compatible with the environment used to build the tools.
-
- In the example above, we created two configurations, one for sun4 and
- one for sun3. The first configuration is expecting to be built in a
- sun4 development environment, to create a sun4 development environment.
- It doesn't necessarily need to be built on a sun4 if a sun4 development
- environment is available elsewhere. Likewise, if the available sun4
- development environment produces executables intended for something
- other than sun4, then the development environment built from this sun4
- configuration will run on something other than a sun4. From the point
- of view of the configuration system and the GNU development tools
- source, this doesn't matter. What matters is that they will be built in
- a sun4 environment.
-
- Similarly, the second configuration given above is expecting to be
- built in a sun3 development environment, to create a sun3 development
- environment.
-
- The development environment produced is a configuration time option,
- just like `$(prefix)'.
-
- ./configure sun4 --prefix=/local --target=sun3
- ./configure sun3 --prefix=/local --target=sun4
-
- In this example, like before, we create two configurations. The
- first is intended to be built in a sun4 environment, in subdirectories,
- to be installed in `/local'. The second is intended to be built in a
- sun3 environment, in subdirectories, to be installed in `/local'.
-
- Unlike the previous example, the first configuration will produce a
- sun3 development environment, perhaps even suitable for building the
- second configuration. Likewise, the second configuration will produce
- a sun4 development environment, perhaps even suitable for building the
- first configuration.
-
- The development environment used to build these configurations will
- determine the machines on which the resulting development environments
- can be used.
-
- File: cfg-paper.info, Node: A Walk Through, Next: Final Notes, Prev: Building Development Environments, Up: Top
-
- A Walk Through
- **************
-
- * Menu:
-
- * Native Development Environments:: Native Development Environments
- * Emulation Environments:: Emulation Environments
- * Simple Cross Environments:: Simple Cross Environments
- * Crossing Into Targets:: Crossing Into Targets
- * Canadian Cross:: Canadian Cross
-
- File: cfg-paper.info, Node: Native Development Environments, Next: Emulation Environments, Prev: A Walk Through, Up: A Walk Through
-
- Native Development Environments
- ===============================
-
- Let us assume for a moment that you have a sun4 and that with your
- sun4 you received a development environment. This development
- environment is intended to be run on your sun4 to build programs that
- can be run on your sun4. You could, for instance, run this development
- environment on your sun4 to build our example desk calculator program.
- You could then run the desk calculator program on your sun4.
-
- The resulting desk calculator program is referred to as a *native*
- program. The development environment itself is composed of native
- programs that, when run, build other native programs. Any other program
- is referred to as *foreign*. Programs intended for other machines are
- foreign programs.
-
- This type of development environment, which is by far the most
- common, is refered to as *native*. That is, a native development
- environment runs on some machine to build programs for that same
- machine. The process of using a native development environment to
- build native programs is called a *native* build.
-
- ./configure sun4
-
- will configure this source such that when built in a sun4 development
- environment, with a development environment that builds programs
- intended to be run on sun4 machines, the programs built will be native
- programs and the resulting development environment will be a native
- development environment.
-
- The development system that came with your sun4 is one such
- environment. Using it to build the GNU Development Tools is a very
- common activity and the resulting development environment is quite
- popular.
-
- make all
-
- will build the tools as configured and will assume that you want to use
- the native development environment that came with your machine.
-
- Using a development environment to build a development environment is
- called *bootstrapping*. The release of the GNU Development Tools is
- capable of bootstrapping itself. This is a very powerful feature that
- we'll return to later. For now, let's pretend that you used the native
- development environment that came with your sun4 to bootstrap the
- release and let's call the new development environment *stage1*.
-
- Why bother? Well, most people find that the GNU development
- environment builds programs that run faster and take up less space than
- the native development environments that came with their machines. Some
- people didn't get development environments with their machines and some
- people just like using the GNU tools better than using other tools.
-
- While you're at it, if the GNU tools produce better programs, maybe
- you should use them to build the GNU tools. So let's pretend that you
- do. Let's call the new development environment *stage2*.
-
- So far you've built a development environment, stage1, and you've
- used stage1 to build a new, faster and smaller development environment,
- stage2, but you haven't run any of the programs that the GNU tools have
- built. You really don't yet know if these tools work. Do you have any
- programs built with the GNU tools? Yes, you do. stage2. What does
- that program do? It builds programs. Ok, do you have any source handy
- to build into a program? Yes, you do. The GNU tools themselves. In
- fact, if you use stage2 to build the GNU tools again the resulting
- programs should be identical to stage2. Let's pretend that you do and
- call the new development environment *stage3*.
-
- You've just completed what's called a *three stage boot*. You now
- have a small, fast, somewhat tested, development environment.
-
- make bootstrap
-
- will do a three stage boot across all tools and will compare stage2 to
- stage3 and complain if they are not identical.
-
- Once built,
-
- make install
-
- will install the development environment in the default location, or in
- `$(prefix)' if you specified an alternate when you configured.
-
- Any development environment that is not a native development
- environment is refered to as a *cross* development environment. There
- are many different types of cross development environments but most
- fall into one of three basic categories.
-
- File: cfg-paper.info, Node: Emulation Environments, Next: Simple Cross Environments, Prev: Native Development Environments, Up: A Walk Through
-
- Emulation Environments
- ======================
-
- The first category of cross development environment is called
- *emulation*. There are two primary types of emulation, but both types
- result in programs that run on the native host.
-
- The first type is *software emulation*. This form of cross
- development environment involves a native program that when run on the
- native host, is capable of interpreting, and in most aspects running, a
- program intended for some other machine. This technique is typically
- used when the other machine is either too expensive, too slow, too fast,
- or not available, perhaps because it hasn't yet been built. The native,
- interpreting program is called a *software emulator*.
-
- The GNU Development Tools do not currently include any software
- emulators. Some do exist and the GNU Development Tools can be
- configured to create simple cross development environments for with
- these emulators. More on this later.
-
- The second type of emulation is when source intended for some other
- development environment is built into a program intended for the native
- host. The concepts of operating system universes and hosted operating
- systems are two such development environments.
-
- File: cfg-paper.info, Node: Simple Cross Environments, Next: Crossing Into Targets, Prev: Emulation Environments, Up: A Walk Through
-
- Simple Cross Environments
- =========================
-
- ./configure sun4 --target=a29k
-
- will configure the tools such that when compiled in a sun4 development
- environment the resulting development environment can be used to create
- programs intended for an a29k. Again, this does not necessarily mean
- that the new development environment can be run on a sun4. That would
- depend on the development environment used to build these tools.
-
- Earlier you saw how to configure the tools to build a native
- development environment, that is, a development environment that runs
- on your sun4 and builds programs for your sun4. Let's pretend that you
- use stage3 to build this simple cross configuration and let's call the
- new development environment gcc-a29k. Remember that this is a native
- build. Gcc-a29k is a collection of native programs intended to run on
- your sun4. That's what stage3 builds, programs for your sun4.
- Gcc-a29k represents an a29k development environment that builds
- programs intended to run on an a29k. But, remember, gcc-a29k runs on
- your sun4. Programs built with gcc-a29k will run on your sun4 only
- with the help of an appropriate software emulator.
-
- Building gcc-a29k is also a bootstrap but of a slightly different
- sort. We call gcc-a29k a *simple cross* environment and using gcc-a29k
- to build a program intended for a29k is called *crossing to* a29k.
- Simple cross environments are the second category of cross development
- environments.
-
- File: cfg-paper.info, Node: Crossing Into Targets, Next: Canadian Cross, Prev: Simple Cross Environments, Up: A Walk Through
-
- Crossing Into Targets
- =====================
-
- ./configure a29k --target=a29k
-
- will configure the tools such that when compiled in an a29k development
- environment, the resulting development environment can be used to create
- programs intended for an a29k. Again, this does not necessarily mean
- that the new development environment can be run on an a29k. That would
- depend on the development environment used to build these tools.
-
- If you've been following along this walk through, then you've already
- built an a29k environment, namely gcc-a29k. Let's pretend you use
- gcc-a29k to build the current configuration.
-
- Gcc-a29k builds programs intended for the a29k so the new development
- environment will be intended for use on an a29k. That is, this new gcc
- consists of programs that are foreign to your sun4. They cannot be run
- on your sun4.
-
- The process of building this configuration is a another bootstrap.
- This bootstrap is also a cross to a29k. Because this type of build is
- both a bootstrap and a cross to a29k, it is sometimes referred to as a
- *cross into* a29k. This new development environment isn't really a
- cross development environment at all. It is intended to run on an a29k
- to produce programs for an a29k. You'll remember that this makes it, by
- definition, an a29k native compiler. *Crossing into* has been
- introduced here not because it is a type of cross development
- environment, but because it is frequently mistaken as one. The process
- is *a cross* but the resulting development environment is a native
- development environment.
-
- You could not have built this configuration with stage3, because
- stage3 doesn't provide an a29k environment. Instead it provides a sun4
- environment.
-
- If you happen to have an a29k lying around, you could now use this
- fresh development environment on the a29k to three-stage these tools
- all over again. This process would look just like it did when we built
- the native sun4 development environment because we would be building
- another native development environment, this one on a29k.
-
- File: cfg-paper.info, Node: Canadian Cross, Prev: Crossing Into Targets, Up: A Walk Through
-
- Canadian Cross
- ==============
-
- So far you've seen that our development environment source must be
- configured for a specific host and for a specific target. You've also
- seen that the resulting development environment depends on the
- development environment used in the build process.
-
- When all four match identically, that is, the configured host, the
- configured target, the environment presented by the development
- environment used in the build, and the machine on which the resulting
- development environment is intended to run, then the new development
- environment will be a native development environment.
-
- When all four match except the configured host, then we can assume
- that the development environment used in the build is some form of
- library emulation.
-
- When all four match except for the configured target, then the
- resulting development environment will be a simple cross development
- environment.
-
- When all four match except for the host on which the development
- environment used in the build runs, the build process is a *cross into*
- and the resulting development environment will be native to some other
- machine.
-
- Most of the other permutations do exist in some form, but only one
- more is interesting to the current discussion.
-
- ./configure a29k --target=sun3
-
- will configure the tools such that when compiled in an a29k development
- environment, the resulting development environment can be used to create
- programs intended for a sun3. Again, this does not necessarily mean
- that the new development environment can be run on an a29k. That would
- depend on the development environment used to build these tools.
-
- If you are still following along, then you have two a29k development
- environments, the native development environment that runs on a29k, and
- the simple cross that runs on your sun4. If you use the a29k native
- development environment on the a29k, you will be doing the same thing we
- did a while back, namely building a simple cross from a29k to sun3.
- Let's pretend that instead, you use gcc-a29k, the simple cross
- development environment that runs on sun4 but produces programs for
- a29k.
-
- The resulting development environment will run on a29k because that's
- what gcc-a29k builds, a29k programs. This development environment will
- produce programs for a sun3 because that is how it was configured. This
- means that the resulting development environment is a simple cross.
-
- There really isn't a common name for this process because very few
- development environments are capable of being configured this
- extensively. For the sake of discussion, let's call this process a
- *Canadian cross*. It's a three party cross, Canada has a three party
- system, hence Canadian Cross.
-
- File: cfg-paper.info, Node: Final Notes, Next: Index, Prev: A Walk Through, Up: Top
-
- Final Notes
- ***********
-
- By *configures*, I mean that links, Makefile, .gdbinit, and
- config.status are built. Configuration is always done from the source
- directory.
-
- `./configure NAME'
- configures this directory, perhaps recursively, for a single
- host+target pair where the host and target are both NAME. If a
- previous configuration existed, it will be overwritten.
-
- `./configure HOSTNAME --target=TARGETNAME'
- configures this directory, perhaps recursively, for a single
- host+target pair where the host is HOSTNAME and target is
- TARGETNAME. If a previous configuration existed, it will be
- overwritten.
-
- * Menu:
-
- * Hacking Configurations:: Hacking Configurations
-
- File: cfg-paper.info, Node: Hacking Configurations, Prev: Final Notes, Up: Final Notes
-
- Hacking Configurations
- ======================
-
- The configure scripts essentially do three things, create
- subdirectories if appropriate, build a `Makefile', and create links to
- files, all based on and tailored to, a specific host+target pair. The
- scripts also create a `.gdbinit' if appropriate but this is not
- tailored.
-
- The Makefile is created by prepending some variable definitions to a
- Makefile template called `Makefile.in' and then inserting host and
- target specific Makefile fragments. The variables are set based on the
- chosen host+target pair and build style, that is, if you use `--srcdir'
- or not. The host and target specific Makefile may or may not exist.
-
- * Makefiles can be edited directly, but those changes will
- eventually be lost. Changes intended to be permanent for a
- specific host should be made to the host specific Makefile
- fragment. This should be in `./config/mh-HOST' if it exists.
- Changes intended to be permanent for a specific target should be
- made to the target specific Makefile fragment. This should be in
- `./config/mt-TARGET' if it exists. Changes intended to be
- permanent for the directory should be made in `Makefile.in'. To
- propogate changes to any of these, either use `make Makefile' or
- `./config.status' or re-configure.
-
- File: cfg-paper.info, Node: Index, Prev: Final Notes, Up: Top
-
- Index
- *****
-
- * Menu:
-
- * Bootstrapping: Native Development Environments.
- * Building: Some Basic Terms.
- * Canadian Cross: Canadian Cross.
- * Compilation: Some Basic Terms.
- * Cross: Native Development Environments.
- * Crossing into: Crossing Into Targets.
- * Crossing to: Simple Cross Environments.
- * Emulation: Emulation Environments.
- * Foreign: Native Development Environments.
- * host: Host Environments.
- * Machines: Some Basic Terms.
- * Native: Native Development Environments.
- * Programs: Some Basic Terms.
- * Simple cross: Simple Cross Environments.
- * Software emulation: Emulation Environments.
- * Software emulator: Emulation Environments.
- * Source: Some Basic Terms.
- * Stage1: Native Development Environments.
- * Stage2: Native Development Environments.
- * Stage3: Native Development Environments.
- * Target: Building Development Environments.
- * Three party cross: Canadian Cross.
- * Three stage boot: Native Development Environments.
-
-
- Tag Table:
- Node: Top1055
- Node: Some Basic Terms2009
- Node: Host Environments2951
- Node: Configuration Time Options5513
- Node: Specifics.8316
- Node: Building Development Environments8934
- Node: A Walk Through11554
- Node: Native Development Environments11972
- Node: Emulation Environments16221
- Node: Simple Cross Environments17579
- Node: Crossing Into Targets19188
- Node: Canadian Cross21381
- Node: Final Notes24208
- Node: Hacking Configurations25003
- Node: Index26418
- End Tag Table
-