Admin/PLATFORMS
author wenzelm
Wed Sep 30 21:32:44 2015 +0200 (2015-09-30)
changeset 61294 2d3d26e9b191
parent 59114 8281f83d286f
child 61741 adf6dd1d490e
permissions -rw-r--r--
renamed jvmpath to platform_path;
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Some notes on multi-platform support of Isabelle
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================================================
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Preamble
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--------
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The general programming model is that of a stylized ML + Scala + POSIX
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environment, with as little system-specific code in user-space tools
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as possible.
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The basic Isabelle system infrastructure provides some facilities to
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make this work, e.g. see the ML and Scala modules File and Path, or
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functions like Isabelle_System.bash.  The settings environment also
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provides some means for portability, e.g. the bash function
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"platform_path" to keep the impression that Windows/Cygwin adheres to
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Isabelle/POSIX standards, although Poly/ML and the JVM are
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Windows-specific things.
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When producing add-on tools, it is important to stay within this clean
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room of Isabelle, and refrain from overly ambitious system hacking.
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The existing Isabelle scripts follow a peculiar style that reflects
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long years of experience in getting system plumbing right.
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Supported platforms
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-------------------
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The following hardware and operating system platforms are officially
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supported by the Isabelle distribution (and bundled tools), with the
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following reference versions (which have been selected to be neither
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too old nor too new):
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  x86-linux         Ubuntu 10.04 LTS
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  x86_64-linux      Ubuntu 10.04 LTS
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  x86_64-darwin     Mac OS X 10.7 Lion (macbroy6)
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                    Mac OS X 10.8 Mountain Lion (macbroy30)
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                    Mac OS X 10.9 Mavericks (macbroy2)
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                    Mac OS X 10.10 Yosemite (macbroy31)
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  x86-cygwin        Cygwin 1.7 (vmbroy9)
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All of the above platforms are 100% supported by Isabelle -- end-users
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should not have to care about the differences (at least in theory).
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Fringe platforms like BSD or Solaris are unsupported.
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32 bit vs. 64 bit platforms
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---------------------------
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Most users have 64 bit hardware and are running a 64 bit operating
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system by default.  For Linux this usually means missing 32 bit shared
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libraries, so native x86_64-linux needs to be used by default, despite
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its doubled space requirements for Poly/ML heaps.  For Mac OS X, the
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x86-darwin personality usually works seamlessly for C/C++ programs,
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but the Java 7 platform is only available for x86_64-darwin.
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Add-on executables are expected to work without manual user
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configuration.  Each component settings script needs to determine the
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platform details appropriately.
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The Isabelle settings environment provides the following variables to
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help configuring platform-dependent tools:
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  ISABELLE_PLATFORM64  (potentially empty)
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  ISABELLE_PLATFORM32
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  ISABELLE_PLATFORM
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The ISABELLE_PLATFORM setting variable refers to the 32 bit version of
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the platform, even on 64 bit hardware.  Using regular bash notation,
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tools may express their preference for 64 bit with a fall-back for 32
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bit as follows:
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  "${ISABELLE_PLATFORM64:-$ISABELLE_PLATFORM32}"
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Moreover note that ML and JVM usually have a different idea of the
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platform, depending on the respective binaries that are actually run.
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Poly/ML 5.5.x performs best in 32 bit mode, even for large
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applications, thanks to its sophisticated heap management.  The JVM
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usually works better in 64 bit mode, which allows its heap to grow
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beyond 2 GB.
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The traditional "uname" Unix tool usually only tells about its own
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executable format, not the underlying platform!
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Dependable system tools
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-----------------------
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The following portable system tools can be taken for granted:
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* GNU bash as uniform shell on all platforms.  The POSIX "standard"
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  shell /bin/sh is *not* appropriate, because there are too many
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  non-standard implementations of it.
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* Perl as largely portable system programming language, with its
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  fairly robust support for processes, signals, sockets etc.
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* Scala with Java 1.8.  Isabelle/Scala irons out many oddities and
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  portability issues of the Java platform.
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Known problems
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--------------
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* Mac OS X: If MacPorts is installed there is some danger that
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  accidental references to its shared libraries are created
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  (e.g. libgmp).  Use otool -L to check if compiled binaries also work
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  without MacPorts.
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* Mac OS X: If MacPorts is installed and its version of Perl takes
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  precedence over /usr/bin/perl in the PATH, then the end-user needs
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  to take care of installing extra modules, e.g. for HTTP support.
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  Such add-ons are usually included in Apple's /usr/bin/perl by
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  default.
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* The Java runtime has its own idea about the underlying platform,
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  which affects Java native libraries in particular.  In
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  Isabelle/Scala the function isabelle.Platform.jvm_platform
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  identifies the JVM platform.  Since a particular Java version is
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  always bundled with Isabelle, the resulting settings also provide
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  some clues about its platform, without running it.
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* Common Unix tools like /bin/sh, /bin/kill, sed, ulimit are
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  notoriously non-portable an should be avoided.