LXR perl/Cross/README.new

   1You're reading ./Cross/README.new, describing Perl cross-compilation process.
   2NOTE: this file will replace ./Cross/README, after the cross-compilation scheme
   3is stabilized.
   4
   5=head1 NAME
   6
   7README.new - Cross-compilation for linux
   8
   9=head1 DESCRIPTION
  10
  11This is second approach to linux cross-compilation, which should allow
  12building full perl and entensions for target platform. Cross-compilation
  13for linux uses similar approach and shares the same files as
  14cross-compilation for WinCE.
  15
  16We refer to HOST as the platform where the build is performed, and to
  17TARGET as where final executables will run.
  18
  19=head2 Basic ideas
  20
  21=head3 common
  22
  23Unlike WinCE, output files from GCC cross-compiler are produced in the same
  24directory where C files are. All TARGET binaries have different extensions
  25so to distinguish HOST and TARGET binaries. Namely, object files for C<arm>
  26cross-compilation will have extension C<.armo>, executable files will have
  27C<.arm>.
  28
  29After typical cross-compilation the following files will be built, among
  30others:
  31
  32  sv.c
  33  sv.o
  34  sv.armo
  35  libperl.arma
  36
  37(this approach may be reconsidered, however.)
  38
  39=head3 build process
  40
  41C<miniperl> is built. This executable is intended to run on HOST, and it
  42will facilitate the remaining build process; all binaries built after it are
  43foreign (TARGET) and should not run locally (HOST).
  44
  45Unlike HOST build, miniperl will not have C<Config.pm> of HOST within reach;
  46it rather will use the C<Config.pm> from the cross-compilation directories.
  47In fact, if the build process does have Config.pm within reach, this is only
  48an indication of a mistake somewhere in the middle.
  49
  50  # following command is okay:
  51  ./miniperl -Ilib -MCross -MConfig -e 1
  52  # following command should cluck, and it is bad if it does not:
  53  ./miniperl -Ilib -MConfig -e 1
  54
  55After C<miniperl> is built, C<configpm> is invoked to create an
  56appropriate C<Config.pm> in the right place and its corresponding
  57C<Cross.pm>.
  58
  59File C<Cross.pm> is dead simple: for given cross-architecture places in @INC
  60a path where perl modules are, and right C<Config.pm> in that place.
  61
  62That said, C<miniperl -Ilib -MConfig -we 1> should report an error, because
  63it cannot find C<Config.pm>. If it does not give an error, a wrong C<Config.pm>
  64is substituted, and resulting binaries will be a mess.
  65
  66C<miniperl -MCross -MConfig -we 1> should run okay, and it will provide a
  67correct C<Config.pm> for further compilations.
  68
  69During extensions build phase, the script C<./ext/util/make_ext_cross> is
  70invoked.
  71
  72All invocations of C<Makefile.PL> are provided with C<-MCross> so to enable
  73cross-compilation.
  74
  75=head2 BUILD
  76
  77=head3 Tools & SDK
  78
  79To compile, you need the following:
  80
  81=over 4
  82
  83=item * TODO
  84
  85=back
  86
  87=head1 Things to be done
  88
  89=over 4
  90
  91=item * better distinguishing of config.h/xconfig.h, dependencies
  92
  93=item * object files created in ./xlib/cross-name/ ?
  94
  95=back
  96