Implement INT34-C

Author: jeongsoolee09

c/cert/src/rules/INT34-C/ExprShiftedbyNegativeOrGreaterPrecisionOperand.ql

@@ -13,7 +13,65 @@
 import cpp
 import codingstandards.c.cert
 
-from
+/* Precision predicate based on a sample implementaion from https://wiki.sei.cmu.edu/confluence/display/c/INT35-C.+Use+correct+integer+precisions */
+int getPrecision(BuiltInType type) {
+  type.(CharType).isExplicitlyUnsigned() and result = 8
+  or
+  type.(ShortType).isExplicitlyUnsigned() and result = 16
+  or
+  type.(IntType).isExplicitlyUnsigned() and result = 32
+  or
+  type.(LongType).isExplicitlyUnsigned() and result = 32
+  or
+  type.(LongLongType).isExplicitlyUnsigned() and result = 64
+  or
+  type instanceof CharType and not type.(CharType).isExplicitlyUnsigned() and result = 7
+  or
+  type instanceof ShortType and not type.(ShortType).isExplicitlyUnsigned() and result = 15
+  or
+  type instanceof IntType and not type.(IntType).isExplicitlyUnsigned() and result = 31
+  or
+  type instanceof LongType and not type.(LongType).isExplicitlyUnsigned() and result = 31
+  or
+  type instanceof LongLongType and not type.(LongLongType).isExplicitlyUnsigned() and result = 63
+}
+
+class MinusNumberLiteral extends UnaryMinusExpr {
+  MinusNumberLiteral() { this.getOperand() instanceof Literal }
+
+  override string toString() { result = "-" + this.getOperand().toString() }
+}
+
+class ForbiddenShiftExpr extends BinaryBitwiseOperation {
+  ForbiddenShiftExpr() {
+    (
+      /* Precision mismatch between operands */
+      getPrecision(this.(LShiftExpr).getLeftOperand().getUnderlyingType()) <=
+        getPrecision(this.(LShiftExpr).getRightOperand().getUnderlyingType()) or
+      getPrecision(this.(RShiftExpr).getLeftOperand().getUnderlyingType()) <=
+        getPrecision(this.(RShiftExpr).getRightOperand().getUnderlyingType()) or
+      /* Shifting by a negative number literal */
+      this.(LShiftExpr).getRightOperand() instanceof MinusNumberLiteral or
+      this.(RShiftExpr).getRightOperand() instanceof MinusNumberLiteral
+    )
+  }
+
+  predicate hasNegativeOperand() {
+    this.(LShiftExpr).getRightOperand() instanceof MinusNumberLiteral or
+    this.(RShiftExpr).getRightOperand() instanceof MinusNumberLiteral
+  }
+}
+
+from ForbiddenShiftExpr badShift, string message
 where
-  not isExcluded(x, TypesPackage::exprShiftedbyNegativeOrGreaterPrecisionOperandQuery()) and
-select
+  not isExcluded(badShift, TypesPackage::exprShiftedbyNegativeOrGreaterPrecisionOperandQuery()) and
+  if badShift.hasNegativeOperand()
+  then
+    message =
+      "The operand " + badShift.getLeftOperand() + " is shifted by a negative expression " +
+        badShift.getRightOperand() + "."
+  else
+    message =
+      "The operand " + badShift.getLeftOperand() + " is shifted by an expression " +
+        badShift.getRightOperand() + " which is greater than or equal to in precision."
+select badShift, message