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-rw-r--r--Build/source/texk/web2c/web2c-sh.in58
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diff --git a/Build/source/texk/web2c/web2c-sh.in b/Build/source/texk/web2c/web2c-sh.in
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+#! @SHELL@
+# web2c-sh: shell script to invoke ${srcdir}/web2c/convert.
+#
+# Copyright (C) 2009 Peter Breitenlohner <tex-live@tug.org>
+#
+# This file is free software; the copyright holder
+# gives unlimited permission to copy and/or distribute it,
+# with or without modifications, as long as this notice is preserved.
+#
+# Convert creates several files, e.g., FOO.c and FOO.h from FOO.p.
+# The naive rule
+# FOO.c FOO.h: FOO.p $(web2c_depend)
+# srcdir=$(srcdir) $(SHELL) $(srcdir)/web2c/convert FOO
+# could run 'convert FOO' twice in parallel and fail. To avoid this
+# and yet recover from removal of FOO.c and/or FOO.h, we use an auxiliary
+# stamp file FOO-web2c and the two rules
+# FOO.c FOO.h: FOO-web2c
+# $(SHELL) ./web2c-sh $@ FOO
+# FOO-web2c: FOO.p $(web2c_depend)
+# $(SHELL) ./web2c-sh $@ FOO
+# Compare Automake manual (info Automake) 27.9: Multiple Outputs
+#
+srcdir=@srcdir@; export srcdir
+target=$1
+base=$2
+stamp=$base-web2c
+case $target in
+ $stamp)
+ # Normal build.
+ rm -f $stamp.tmp
+ echo timestamp >$stamp.tmp
+ echo "@SHELL@ $srcdir/web2c/convert $base"
+ @SHELL@ $srcdir/web2c/convert $base || exit 1
+ mv -f $stamp.tmp $stamp
+ ;;
+ *)
+ # Recover from removal of $target
+ test -f $target && exit 0
+ trap "rm -rf $stamp $stamp.lock" 1 2 13 15
+ if mkdir $stamp.lock 2>/dev/null; then
+ # Code executed by the first process.
+ rm -f $stamp $stamp.tmp
+ echo timestamp >$stamp.tmp
+ echo "@SHELL@ $srcdir/web2c/convert $base"
+ @SHELL@ $srcdir/web2c/convert $base || exit 1
+ mv -f $stamp.tmp $stamp
+ rmdir $stamp.lock
+ else
+ # Code executed by the follower processes.
+ # Wait until the first process is done.
+ while test -d $stamp.lock; do sleep 1; done
+ # Succeed if and only if the first process succeeded.
+ test -f $stamp; exit $?
+ fi
+ ;;
+esac
+
+exit 0