Merge pull request #5334 from Marcono1234/marcono1234/improve-constant-loop-condition

Java: Improve constant-loop-condition

Author: aschackmull

java/ql/src/Likely Bugs/Termination/ConstantLoopCondition.ql

@@ -79,7 +79,11 @@ where
   ) and
   // And `cond` does not use method calls, field reads, or array reads.
   not exists(MethodAccess ma | ma.getParent*() = cond) and
-  not exists(FieldRead fa | fa.getParent*() = cond) and
+  not exists(FieldRead fa |
+    // Ignore if field is final
+    not fa.getField().isFinal() and
+    fa.getParent*() = cond
+  ) and
   not exists(ArrayAccess aa | aa.getParent*() = cond)
 select cond, "$@ might not terminate, as this loop condition is constant within the loop.", loop,
   "Loop"

java/ql/test/query-tests/ConstantLoopCondition/A.java

@@ -1,4 +1,6 @@
 class A {
+  final boolean cond = otherCond();
+
   boolean otherCond() { return 3 > 5; }
 
   void f(int initx) {
@@ -30,5 +32,9 @@ void f(int initx) {
     while(initx > 0) { // OK: loop used as an if-statement
       break;
     }
+
+    while (cond) { // BAD: read of final field
+      i++;
+    }
   }
 }

java/ql/test/query-tests/ConstantLoopCondition/ConstantLoopCondition.expected

@@ -1,3 +1,4 @@
-| A.java:6:11:6:15 | !... | $@ might not terminate, as this loop condition is constant within the loop. | A.java:6:5:6:16 | stmt | Loop |
-| A.java:13:11:13:15 | ... > ... | $@ might not terminate, as this loop condition is constant within the loop. | A.java:12:5:12:19 | stmt | Loop |
-| A.java:27:20:27:32 | ... < ... | $@ might not terminate, as this loop condition is constant within the loop. | A.java:27:5:27:38 | stmt | Loop |
+| A.java:8:11:8:15 | !... | $@ might not terminate, as this loop condition is constant within the loop. | A.java:8:5:8:16 | stmt | Loop |
+| A.java:15:11:15:15 | ... > ... | $@ might not terminate, as this loop condition is constant within the loop. | A.java:14:5:14:19 | stmt | Loop |
+| A.java:29:20:29:32 | ... < ... | $@ might not terminate, as this loop condition is constant within the loop. | A.java:29:5:29:38 | stmt | Loop |
+| A.java:36:12:36:15 | cond | $@ might not terminate, as this loop condition is constant within the loop. | A.java:36:5:36:16 | stmt | Loop |