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=head1 NAME
makepp_compatibility -- Compatibility list for makepp
=for vc $Id: makepp_compatibility.pod,v 1.17 2008/08/09 09:34:03 pfeiffer Exp $
=head1 DESCRIPTION
=head2 Perl Version vs. System
The many Perl versions available and still installed on many machines come
with various subtle bugs.  We have tried to work around most of them, but a
few remain.  We have a test suite of around 75 tests, all of which usually
pass.  On some platforms lacking some features, notably Cygwin, a few tests
are explicitly skipped.  This table shows with what version this has been
tested where, and whether it was successful.  We would like to hear of your
results on other platforms too!
=for html
<style type="text/css">
.good { white-space: nowrap; font-family: sans-serif; background-image: url(pre.png); background-repeat: repeat-y }
.soso { white-space: nowrap; font-family: sans-serif; background-color: #c0d0ff }
.bad  { white-space: nowrap; font-family: sans-serif; background-color: #ff4000 }
</style>
<ul>
<li>successful: <b class="good">&nbsp;x&nbsp;</b></li>
<li>mostly successful with footnote: <b class="soso">&nbsp;x<sup>*)</sup></b></li>
<!--li>failed: <b class="bad">&nbsp;<i>/</i>&nbsp;</b></li-->
</ul>
<table border="1" cellspacing="3" cellpadding="3">
=for comment
The following table, where each table row must be separated by an empty line,
has the structure " OS#x|x|x#x|x|...#".  Here 'x' means success, '/' means
failure, empty means not tested, and anything else is a footnote link to the
list below.  The first two lines are special, based on the OS field being
empty.  This is converted to html by install.pl and readable as is in other
formats.
                #||     5.6             #||||||||                       5.8                                     # 5.10  #
                # .0    | .1    | .2    # .0    | .1    | .2    | .3    | .4    | .5    | .6    | .7    | .8    # .0    #
 GNU/Linux (x86)# x     | x     | req   # x     | x     | x     | x     | x     |       | x     | x     | x     # x     #
 GNU/Linux (amd64)#     |       |       #       |       |       |       |       | x     |       |       |       #       #
 GNU/Linux (alpha)#     | x     |       #       |       |       |       |       |       |       |       |       #       #
 FreeBSD (x86)  #       | x     | x     #       |       |       |       |       |       |       |       | x     # x     #
 NetBSD (alpha) #       |       |       #       |       |       |       |       |       |       |       |       # x     #
 OpenBSD (x86)  #       |       |       # x     |       |       |       |       |       |       |       |       #       #
 AIX (PPC)      #       |       |       #       | x     | x     |       |       |       |       | x     | x     #       #
 Darwin (PPC)   # x     |       |       #       |       |       |       |       |       |       |       |       #       #
 HP/UX (IA64)   #       |       |       # HPUX  |       |       | HPUX  |       |       |       |       |       #       #
 Irix           #       |       |       #       |       |       |       |       |       |       |       | x     #       #
 Reliant (Mips) # Nest  | Nest  |       #       |       |       |       |       |       |       |       |       #       #
 Solaris (Sparc)# x     | req   |       # x     | x     | x     | x     | x     | x     | x     | x     | x     # x     #
 Solaris (64bit)#       |       |       #       | x     |       |       |       |       |       |       | x     #       #
 Solaris (x86)  #       | x     |       #       | x     |       |       |       |       |       |       | x     #       #
 BS2000 (S/390) #       | x     |       #       | x     |       |       |       |       |       |       |       #       #
 z/OS USS (S/390)#      |       |       #       |       |       |       |       |       |       |       | zOS   #       #
 Cygwin (x86)   #       |       |       #       |       |       |       |       |       |       | Win   | x     # x     #
 MinGW MSYS     #       | Win   |       #       |       |       |       |       |       |       |       |       #       #
 Windows        # Win   | Win   |       # x     | x     | x     | x     | x     |       | x     | x     | x     # x     #
=for html </table>
=over
=item HPUX
Perl at least up to V5.8.8 has a 64bitall bug on HP/UX that hurts makepp
badly.  If it recognized that its running on a 64 bit Perl, it will rewrite
several sources so as to have a workaround for this problem.
=item req
Some instances of 5.6 at least on Linux and Solaris will dump in a Perl
C<require> statement.  Strangely this only happens in one test, so you are
probably ok using these Perls.
=item Win
There are 3 different Perl environments on Windows, which normally extend one
another when installed in parallel.  Here they have been tested with a minimal
PATH, so as to separate them completely:
=over
=item *
Cygwin fairly closely emulates GNU/Linux and gives the best results.  Perl
5.8.7 has a small problem with environment vars, making one test fail.  In the
long gone past, parallel builds didn't work, but it hasn't be verified which
version of Cygwin or Perl made them usable.
=item *
MinGW stays close to Windows, giving it only a Unixy look and feel.  It has a
clever workaround for lack of symbolic links, namely copying instead (C<&ln>
has stolen this idea).  Alas this is not good enough for the B<repository>
mechanism, so that isn't available, in addition to the Cygwin deficiencies.
Strangely they are still rebuilding solely 5.6.1 (which fails only in the
makeppgraph test), at least with MD5 support.  But with very few packages
(MSYS) to install, this gives you a nice small Unix-like environment.
=item *
On ActiveState Perl with only native Windows most customary Unix commands are
missing, and the "shell" is extremely primitive.  A maximal use of makepp's
builtin commands and embedded Perl can increase makefile portability.  While
Windows programs can handle normal slashes as directory separators, this does
not work for command names.  Those should be written as F<dir$/command>, where
C<$/> is a forward or backward slash, depending on the environment.  If you
tell makepp, via the SHELL variable, where to find a a Unix-like Shell, you
don't have these worries.
It cannot do smart recursive makes (but who would want them, since they are
known to be a broken paradigm) and B<parallel> builds.  Perl 5.6.0 fails on
quite a few tests, especially with $SHELL, 5.6.1 fails on two tests.  It will
rewrite FileInfo.pm so as to have a needed workaround for an lstat bug.
=back
=item zOS
On z/OS Unix System Services smart recursive make doesn't work.  If your
compiler is picky about option order, you may have to write your own rules.
(Perl 5.10.0 is not compilable on an Ebcdic system and for 5.8.8 in
miniperlmain.c you may have to remove the silly "(void)env;".)
=item Nest
Some old compilers do not like nested comments.  Since
F<additional_tests/2006_03_23_c_comments.test> looks at all kinds of
constellations, and verifies it's conclusions with the compiler, this test can
fail if you do not use gcc.
=back
=head2 File Systems
Various special file systems have unusual properties, giving makepp a hard
time when working on them:
=over
=item NFS
NFS may reorder file operations at its discretion, leading to unexpected
relationships between time stamps.  This is relevant for the build info meta
files, which makepp stores alongside each file.  Especially in build caches,
with their concurrent access, some workaround handling was necessary, but it
seems to work fine.
=item Windows CIFS on Gnu/Linux
A few special characters are not allowed in filenames.  Links are emulated by
copying while symbolic linking fails.  Apparently write operations come back
before they are visible on disk, which confuses makepp about the success of
the commands it executes.  Several tests fail due to this.  On the bright
side, timestamps have a precision of 100 nanoseconds (though the observed
obtainable differences are only about a centisecond).  This is much better
than most older Unix file systems -- alas perl's C<stat> function has no
access to this very welcome precision.
=item Windows Server Share on Cygwin
The same CIFS disk that was works so badly on Linux, passes all tests on
Cygwin.  Possibly there are options that might improve something.
=item Unix SMBFS on Gnu/Linux
Linking and symbolic linking fails.  No other tests fail.  I have no access to
a more realistic Windows SMB server, where the situation might be different.
=item VFAT on Gnu/Linux
A few special characters are not allowed in filenames.  Linking and symbolic
linking fails.  The file permission mask and owner are mount options, while
the time stamps are not settable.  One test fails.
=back
=head1 AUTHOR
Daniel Pfeiffer (occitan@esperanto.org)