[m-rev.] For review: Have configure decide whether to install the Java grade

[James Goddard]

> We currently rely on some features of J2SE 1.2, right?
> 
> I think it would be a good idea for configure to test
> that you can compile and run a simple test program conftest.java
> which uses those features, similar to the way we check $BOOTSTRAP_MC.

I've added such a program, but instead of checking for each required
feature we use from J2SE 1.2 (of which I believe there are many many)
I've got it just checking the appropriate runtime constant for the
version (java.specification.version) is  >= 1.2.  All 'compatible' Java
implementations should have this constant, since it's part of the API
specification.
I've also added a check for the java interpreter.

--------------------------------------------------------------------
diff -u aclocal.m4 aclocal.m4
--- aclocal.m4	9 Feb 2004 07:12:48 -0000
+++ aclocal.m4	10 Feb 2004 05:41:14 -0000
@@ -286,18 +286,61 @@
 AC_DEFUN(MERCURY_CHECK_JAVA,
 [
 AC_PATH_PROG(JAVAC, javac)
+AC_PATH_PROG(JAVAI, java)
 
-AC_MSG_CHECKING(for Java SDK)
 AC_CACHE_VAL(mercury_cv_java, [
-if test "$JAVAC" != ""; then
-        mercury_cv_java="yes"
+if test "$JAVAC" != "" -a "$JAVAI" != ""; then
+	AC_MSG_CHECKING(if the above Java SDK works and is sufficiently recent)
+	cat > conftest.java << EOF
+		// This program simply retrieves the constant
+		// specifying the version number of the Java SDK and
+		// checks it is at least 1.2, printing "Hello, world"
+		// if successful.
+		public class conftest {
+		    public static void main (String[[]] args) {
+			float	version;
+			String	strVer = System.getProperty(
+					"java.specification.version");
+
+			try {
+				version = Float.valueOf(strVer).floatValue();
+			}
+			catch (NumberFormatException e) {
+				System.out.println("ERROR: \"java." +
+						"specification.version\" " +
+						"constant has incorrect " +
+						"format.\nGot \"" + strVer +
+						"\", expected a number.");
+				version = 0f;
+			}
+
+			if (version >= 1.2f) {
+				System.out.println("Hello, world\n");
+			} else {
+				System.out.println("Nope, sorry.\n");
+			}
+		    }
+		}
+EOF
+	if
+		echo $JAVAC conftest.java >&AC_FD_CC 2>&1 &&
+		$JAVAC conftest.java >&AC_FD_CC 2>&1 &&
+		echo $JAVAI conftest > conftest.out 2>&AC_FD_CC &&
+		$JAVAI conftest > conftest.out 2>&AC_FD_CC &&
+		test "`tr -d '\015' < conftest.out`" = "Hello, world"
+	then
+		mercury_cv_java="yes"
+	else
+		mercury_cv_java="no"
+	fi
+	AC_MSG_RESULT($mercury_cv_java)
 else
-        mercury_cv_java="no"
+	mercury_cv_java="no"
 fi
 ])
-AC_MSG_RESULT($mercury_cv_java)
 
 AC_SUBST(JAVAC)
+AC_SUBST(JAVAI)
 ])
 
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