Use loop counter definition from CERT

Author: rvermeulen

c/cert/src/rules/FLP30-C/FloatingPointLoopCounters.ql

@@ -16,15 +16,36 @@ import cpp
 import codingstandards.c.cert
 import codingstandards.cpp.Loops
 
-from Loop loop
+/*
+ *  A variable that is increased or decreased by a fixed amount on each iteration.
+ */
+
+class InductionVariable extends Variable {
+  Loop loop;
+  Expr update;
+
+  InductionVariable() {
+    update.getParent+() = loop and
+    (
+      update.(AssignArithmeticOperation).getRValue().isConstant() and
+      update.(AssignArithmeticOperation).getLValue() = this.getAnAccess()
+      or
+      exists(BinaryArithmeticOperation binop |
+        update.(Assignment).getLValue() = this.getAnAccess() and
+        update.(Assignment).getRValue() = binop and
+        binop.getAnOperand() = this.getAnAccess() and
+        binop.getAnOperand().isConstant()
+      )
+      or
+      update.(CrementOperation).getOperand() = this.getAnAccess()
+    )
+  }
+}
+
+from Loop loop, InductionVariable loopCounter, ComparisonOperation comparison
 where
   not isExcluded(loop, Statements4Package::floatingPointLoopCountersQuery()) and
-  exists(WhileStmt while |
-    while.getCondition().getType() instanceof FloatType and
-    loop = while
-  )
-  or
-  exists(ForStmt for, Variable counter |
-    isForLoopWithFloatingPointCounters(for, counter) and for = loop
-  )
-select loop, "Loop $@ has a floating-point type.", loop.getControllingExpr(), "counter"
+  loop.getControllingExpr() = comparison and
+  comparison.getAnOperand() = loopCounter.getAnAccess() and
+  loopCounter.getType() instanceof FloatingPointType
+select loop, "Loop using a $@ of type floating-point.", loopCounter, "loop counter"

c/cert/test/rules/FLP30-C/FloatingPointLoopCounters.expected

@@ -1,2 +1,3 @@
-| test.c:3:3:4:3 | for(...;...;...) ... | Loop $@ has a floating-point type. | test.c:3:18:3:26 | ... < ... | counter |
-| test.c:5:3:6:3 | while (...) ... | Loop $@ has a floating-point type. | test.c:5:10:5:17 | ... - ... | counter |
+| test.c:3:3:4:3 | for(...;...;...) ... | Loop using a $@ of type floating-point. | test.c:2:9:2:9 | f | loop counter |
+| test.c:5:3:7:3 | while (...) ... | Loop using a $@ of type floating-point. | test.c:2:9:2:9 | f | loop counter |
+| test.c:9:3:11:22 | do (...) ... | Loop using a $@ of type floating-point. | test.c:2:9:2:9 | f | loop counter |

c/cert/test/rules/FLP30-C/test.c

@@ -2,14 +2,25 @@ void f1() {
   float f = 0.0F;
   for (f = 0.0F; f < 10.0F; f += 0.2F) { // NON_COMPLIANT
   }
-  while (f - 0.0F) { // NON_COMPLIANT
+  while (f < 10.0F) { // NON_COMPLIANT
+    f = f * 2.0F;
   }
+
+  do {
+    f *= 2.0F;
+  } while (f < 10.0F); // NON_COMPLIANT
 }
 
 void f2() {
 
   for (int i = 0; i < 10; i++) { // COMPLIANT
   }
-  while (4 - 4) { // COMPLIANT
+  int j = 0;
+  while (j < 10) { // COMPLIANT
+    j = j * 2;
   }
+
+  do {
+    j++;
+  } while (j < 10); // COMPLIANT
 }