autoconf: Create disconnected branch for CI scripts.

https://github.com/libsdl-org/autoconf/commit/c2e8b0ee81e9f523a1aebaa4a80cba1af660395a

From c2e8b0ee81e9f523a1aebaa4a80cba1af660395a Mon Sep 17 00:00:00 2001
From: Zack Weinberg <[EMAIL REDACTED]>
Date: Wed, 15 Sep 2021 17:15:19 -0400
Subject: [PATCH] Create disconnected branch for CI scripts.
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
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I don’t know if this will be the way to maintain them long term, but
this keeps them out of the hair of people working on trunk while
they’re experimental.

Currently only has metainformation and a script to produce a report on
how a CI environment is set up (vital for debugging).

BuildCommon.pm was originally written by me for
libxcrypt (https://github.com/besser82/libxcrypt).  That project uses
very permissive licensing when possible, so it is under CC0 rather
than GPL.
---
 BuildCommon.pm  | 304 ++++++++++++++++++++++
 COPYINGv3       | 674 ++++++++++++++++++++++++++++++++++++++++++++++++
 README          |  53 ++++
 log_environment | 101 ++++++++
 4 files changed, 1132 insertions(+)
 create mode 100644 BuildCommon.pm
 create mode 100644 COPYINGv3
 create mode 100644 README
 create mode 100755 log_environment

diff --git a/BuildCommon.pm b/BuildCommon.pm
new file mode 100644
index 00000000..2f598c42
--- /dev/null
+++ b/BuildCommon.pm
@@ -0,0 +1,304 @@
+# Written by Zack Weinberg <zackw at panix.com> in 2017, 2020, 2021.
+# To the extent possible under law, Zack Weinberg has waived all
+# copyright and related or neighboring rights to this work.
+#
+# See https://creativecommons.org/publicdomain/zero/1.0/ for further
+# details.
+
+package BuildCommon;
+
+use v5.14;    # implicit use strict, use feature ':5.14'
+use warnings FATAL => 'all';
+use utf8;
+use open qw(:utf8);
+no  if $] >= 5.018, warnings => 'experimental::smartmatch';
+no  if $] >= 5.022, warnings => 'experimental::re_strict';
+use if $] >= 5.022, re       => 'strict';
+
+use Cwd qw(realpath);
+use File::Spec::Functions qw(
+    catfile
+    catpath
+    file_name_is_absolute
+    path
+    splitpath
+);
+use FindBin ();
+use POSIX   ();
+
+our @EXPORT_OK;
+use Exporter qw(import);
+
+BEGIN {
+    @EXPORT_OK = qw(
+        ensure_C_locale
+        error
+        popen
+        run
+        sh_split
+        sh_quote
+        subprocess_error
+        which
+    );
+}
+
+#
+# Utilities for dealing with subprocesses.
+#
+
+# Diagnostics: report some kind of catastrophic internal error.
+# Exit code 99 tells the Automake test driver to mark a test as
+# 'errored' rather than 'failed'.
+sub error {    ## no critic (Subroutines::RequireArgUnpacking)
+    my $msg = join q{ }, @_;
+    print {*STDERR} $FindBin::Script, ': ERROR: ', $msg, "\n";
+    exit 99;
+}
+
+# Like 'error', but the problem was with a subprocess, detected upon
+# trying to start the program named as @_.
+sub invocation_error {    ## no critic (Subroutines::RequireArgUnpacking)
+    my $err = "$!";
+    my $cmd = join q{ }, @_;
+    error("failed to invoke $cmd: $err");
+}
+
+# Like 'error', but the problem was with a subprocess, detected upon
+# termination of the program named as @_; interpret both $! and $?
+# appropriately.
+sub subprocess_error {    ## no critic (Subroutines::RequireArgUnpacking)
+    my $syserr = $!;
+    my $status = $?;
+    my $cmd    = join q{ }, @_;
+    if ($syserr) {
+        error("system error with pipe to $cmd: $syserr");
+
+    } elsif ($status == 0) {
+        return;
+
+    } elsif (($status & 0xFF) == 0) {
+        # we wouldn't be here if the exit status was zero
+        error("$cmd: exit " . ($status >> 8));
+
+    } else {
+        my $sig = ($status & 0x7F);
+        # Neither Perl core nor the POSIX module exposes strsignal.
+        # This is the least terrible kludge I can presently find;
+        # it decodes the numbers to their <signal.h> constant names
+        # (e.g. "SIGKILL" instead of "Killed" for signal 9).
+        # Linear search through POSIX's hundreds of symbols is
+        # acceptable because this function terminates the process,
+        # so it can only ever be called once per run.
+        my $signame;
+        while (my ($name, $glob) = each %{'POSIX::'}) {
+            if ($name =~ /^SIG(?!_|RT)/ && (${$glob} // -1) == $sig) {
+                $signame = $name;
+                last;
+            }
+        }
+        $signame //= "signal $sig";
+        error("$cmd: killed by $signame");
+    }
+}
+
+# Split a string into words, exactly the way the Bourne shell would do
+# it, with the default setting of IFS, when the string is the result
+# of a variable expansion.  If any of the resulting words would be
+# changed by filename expansion, throw an exception, otherwise return
+# a list of the words.
+#
+# Note: the word splitting process does *not* look for nested
+# quotation, substitutions, or operators.  For instance, if a
+# shell variable was set with
+#    var='"ab cd"'
+# then './a.out $var' would pass two arguments to a.out:
+# '"ab' and 'cd"'.
+sub sh_split {
+    my @words = split /[ \t\n]+/, shift;
+    for my $w (@words) {
+        die "sh_split: '$w' could be changed by filename expansion"
+            if $w =~ / (?<! \\) [\[?*] /ax;
+    }
+    return @words;
+}
+
+# Quote a string, or list of strings, so that they will pass
+# unmolested through the shell.  Avoids adding quotation whenever
+# possible.  Algorithm copied from Python's shlex.quote.
+sub sh_quote {    ## no critic (Subroutines::RequireArgUnpacking)
+    my @quoted;
+    for my $w (@_) {
+        if ($w =~ m{[^\w@%+=:,./-]}a) {
+            my $q = $w;
+            $q =~ s/'/'\\''/g;
+            $q =~ s/^/'/;
+            $q =~ s/$/'/;
+            push @quoted, $q;
+        } else {
+            push @quoted, $w;
+        }
+    }
+    return wantarray ? @quoted : $quoted[0];
+}
+
+# Emit a logging message for the execution of a subprocess whose
+# argument vector is @_.
+sub log_execution {    ## no critic (Subroutines::RequireArgUnpacking)
+    print {*STDERR} '+ ', join(q{ }, sh_quote(@_)), "\n";
+    return;
+}
+
+# Run, and log execution of, a subprocess, with no I/O redirection.
+# @_ should be an argument vector.
+# Calls invocation_error() and/or subprocess_error() as appropriate.
+# Does *not* call which(); do that yourself if you need it.
+sub run {    ## no critic (Subroutines::RequireArgUnpacking)
+    die 'run: no command to execute'
+        if scalar(@_) == 0;
+    log_execution(@_);
+    my $status = system { $_[0] } @_;
+
+    return                  if $status == 0;
+    invocation_error($_[0]) if $status == -1;
+    subprocess_error(@_);
+}
+
+# Run, and log execution of, a subprocess.  @_ should be one of the
+# open modes that creates a pipe, followed by an argument vector.
+# An anonymous filehandle for the pipe is returned.
+# Calls invocation_error() if open() fails.
+# Does *not* call which(); do that yourself if you need it.
+sub popen {
+    my ($mode, @args) = @_;
+    die "popen: inappropriate mode argument '$mode'"
+        unless $mode eq '-|' || $mode eq '|-';
+    die 'popen: no command to execute'
+        if scalar(@args) == 0;
+
+    log_execution(@args);
+    open my $fh, $mode, @args
+        or invocation_error($args[0]);
+    return $fh;
+}
+
+# Force use of the C locale for this process and all subprocesses.
+# This is necessary because subprocesses' output may be locale-
+# dependent.  If the C.UTF-8 locale is available, it is used,
+# otherwise the plain C locale.  Note that we do *not*
+# 'use locale' here or anywhere else!
+sub ensure_C_locale {
+    use POSIX qw(setlocale LC_ALL);
+
+    for my $k (keys %ENV) {
+        if ($k eq 'LANG' || $k eq 'LANGUAGE' || $k =~ /^LC_/) {
+            delete $ENV{$k};
+        }
+    }
+    if (defined(setlocale(LC_ALL, 'C.UTF-8'))) {
+        $ENV{LC_ALL} = 'C.UTF-8'; ## no critic (RequireLocalizedPunctuationVars)
+    } elsif (defined(setlocale(LC_ALL, 'C'))) {
+        $ENV{LC_ALL} = 'C';       ## no critic (RequireLocalizedPunctuationVars)
+    } else {
+        error("could not set 'C' locale: $!");
+    }
+    return;
+}
+
+# Clean up $ENV{PATH}, and return the cleaned path as a list.
+sub clean_PATH {
+    state @path;
+    if (!@path) {
+        for my $d (path()) {
+            # Discard all entries that are not absolute paths.
+            next unless file_name_is_absolute($d);
+            # Discard all entries that are not directories, or don't
+            # exist.  (This is not just for tidiness; realpath()
+            # behaves unpredictably if called on a nonexistent
+            # pathname.)
+            next unless -d $d;
+            # Resolve symlinks in all remaining entries.
+            $d = realpath($d);
+            # Discard duplicates.
+            push @path, $d unless grep { $_ eq $d } @path;
+        }
+        error('nothing left after cleaning PATH')
+            unless @path;
+
+        # File::Spec knows internally whether $PATH is colon-separated
+        # or semicolon-separated, but it won't tell us.  Assume it's
+        # colon-separated unless the first element of $PATH has a
+        # colon in it (and is therefore probably a DOS-style absolute
+        # path, with a drive letter).
+        my $newpath;
+        if ($path[0] =~ /:/) {
+            $newpath = join ';', @path;
+        } else {
+            $newpath = join ':', @path;
+        }
+        $ENV{PATH} = $newpath;    ## no critic (RequireLocalizedPunctuationVars)
+    }
+    return @path;
+}
+
+# Locate a program that we need.
+# $_[0] is the name of the program along with any options that are
+# required to use it correctly.  Split this into an argument list,
+# exactly as /bin/sh would do it, and then search $PATH for the
+# executable.  If we find it, return a list whose first element is
+# the absolute pathname of the executable, followed by any options.
+# Otherwise return an empty list.
+sub which {
+    my ($command) = @_;
+    my @PATH = clean_PATH();
+
+    # Split the command name from any options attached to it.
+    my ($cmd, @options) = sh_split($command);
+    my ($vol, $path, $file) = splitpath($cmd);
+
+    if ($file eq 'false') {
+        # Special case: the command 'false' is never considered to be
+        # available.  Autoconf sets config variables like $CC and $NM to
+        # 'false' if it can't find the requested tool.
+        return ();
+
+    } elsif ($file ne $cmd) {
+        # $cmd was not a bare filename.  Do not do path search, but do
+        # verify that $cmd exists and is executable, then convert it
+        # to a canonical absolute path.
+        #
+        # Note: the result of realpath() is unspecified if its
+        # argument does not exist, so we must test its existence
+        # first.
+        #
+        # Note: if $file is a symlink, we must *not* resolve that
+        # symlink, because that may change the name of the program,
+        # which in turn may change what the program does.
+        # For instance, suppose $CC is /usr/lib/ccache/cc, and this
+        # 'cc' is a symlink to /usr/bin/ccache.  Resolving the symlink
+        # will cause ccache to be invoked as 'ccache' instead of 'cc'
+        # and it will error out because it's no longer being told
+        # it's supposed to run the compiler.
+        if (-f -x $cmd) {
+            return (catfile(realpath(catpath($vol, $path, q{})), $file),
+                @options);
+        } else {
+            return ();
+        }
+
+    } else {
+        for my $d (@PATH) {
+            my $cand = catfile($d, $cmd);
+            if (-f -x $cand) {
+                # @PATH came from clean_PATH, so all of the directories
+                # have already been canonicalized.  If the last element
+                # of $cand is a symlink, we should *not* resolve it (see
+                # above).  Therefore, we do not call realpath here.
+                return ($cand, @options);
+            }
+        }
+        return ();
+
+    }
+}
+
+1;
diff --git a/COPYINGv3 b/COPYINGv3
new file mode 100644
index 00000000..f288702d
--- /dev/null
+++ b/COPYINGv3
@@ -0,0 +1,674 @@
+                    GNU GENERAL PUBLIC LICENSE
+                       Version 3, 29 June 2007
+
+ Copyright (C) 2007 Free Software Foundation, Inc. <https://fsf.org/>
+ Everyone is permitted to copy and distribute verbatim copies
+ of this license document, but changing it is not allowed.
+
+                            Preamble
+
+  The GNU General Public License is a free, copyleft license for
+software and other kinds of works.
+
+  The licenses for most software and other practical works are designed
+to take away your freedom to share and change the works.  By contrast,
+the GNU General Public License is intended to guarantee your freedom to
+share and change all versions of a program--to make sure it remains free
+software for all its users.  We, the Free Software Foundation, use the
+GNU General Public License for most of our software; it applies also to
+any other work released this way by its authors.  You can apply it to
+your programs, too.
+
+  When we speak of free software, we are referring to freedom, not
+price.  Our General Public Licenses are designed to make sure that you
+have the freedom to distribute copies of free software (and charge for
+them if you wish), that you receive source code or can get it if you
+want it, that you can change the software or use pieces of it in new
+free programs, and that you know you can do these things.
+
+  To protect your rights, we need to prevent others from denying you
+these rights or asking you to surrender the rights.  Therefore, you have
+certain responsibilities if you distribute copies of the software, or if
+you modify it: responsibilities to respect the freedom of others.
+
+  For example, if you distribute copies of such a program, whether
+gratis or for a fee, you must pass on to the recipients the same
+freedoms that you received.  You must make sure that they, too, receive
+or can get the source code.  And you must show them these terms so they
+know their rights.
+
+  Developers that use the GNU GPL protect your rights with two steps:
+(1) assert copyright on the software, and (2) offer you this License
+giving you legal permission to copy, distribute and/or modify it.
+
+  For the developers' and authors' protection, the GPL clearly explains
+that there is no warranty for this free software.  For both users' and
+authors' sake, the GPL requires that modified versions be marked as
+changed, so that their problems will not be attributed erroneously to
+authors of previous versions.
+
+  Some devices are designed to deny users access to install or run
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+  The precise terms and conditions for copying, distribution and
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+  "This License" refers to version 3 of the GNU General Public License.
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+includes interface definition files associated with source files for
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+subprograms and other parts of the work.
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+Source.
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+same work.
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+covered work is covered by this License only if the output, given its
+content, constitutes a covered work.  This License acknowledges your
+rights of fair use or other equivalent, as provided by copyright law.
+
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+convey, without conditions so long as your license otherwise remains
+in force.  You may convey covered works to others for the sole purpose
+of having them make modifications exclusively for you, or provide you
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+circumvention of technological measures to the extent such circumvention
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+  You may convey verbatim copies of the Program's source code as you
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+  "Additional permissions" are terms that supplement the terms of this
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(Patch may be truncated, please check the link at the top of this post.)