6882235: invalid exponent causes silent javac crash

Reviewed-by: darcy

src/share/classes/com/sun/tools/javac/parser/JavacParser.java

@@ -593,7 +593,7 @@ public class JavacParser implements Parser {
 //where
         boolean isZero(String s) {
             char[] cs = s.toCharArray();
-            int base = ((Character.toLowerCase(s.charAt(1)) == 'x') ? 16 : 10);
+            int base = ((cs.length > 1 && Character.toLowerCase(cs[1]) == 'x') ? 16 : 10);
             int i = ((base==16) ? 2 : 0);
             while (i < cs.length && (cs[i] == '0' || cs[i] == '.')) i++;
             return !(i < cs.length && (Character.digit(cs[i], base) > 0));

test/tools/javac/T6882235.java

+/*
+ * @test /nodynamiccopyright/
+ * @bug 6882235
+ * @summary invalid exponent causes silent javac crash
+ *
+ * @compile/fail T6882235.java
+ * @compile/fail/ref=T6882235.out -XDrawDiagnostics T6882235.java
+ */
+
+class T6882235 {
+    int i = ;           // invalid expression
+    float f = 0e*;      // invalid exponent, should not crash compiler
+    int j = ;           // invalid expression
+}

test/tools/javac/T6882235.out

+T6882235.java:11:13: compiler.err.illegal.start.of.expr
+T6882235.java:12:15: compiler.err.malformed.fp.lit
+T6882235.java:12:18: compiler.err.illegal.start.of.expr
+T6882235.java:13:13: compiler.err.illegal.start.of.expr
+4 errors