CPP: Fix false positive.

geoffw0 · geoffw0 · commit cbe69f2daf80 · 2019-01-09T13:59:24.000Z
diff --git a/cpp/ql/src/Likely Bugs/Conversion/LossyFunctionResultCast.ql b/cpp/ql/src/Likely Bugs/Conversion/LossyFunctionResultCast.ql
@@ -10,11 +10,30 @@
  */
 import cpp
 
+predicate whitelist(string fName) {
+  fName = "ceil" or
+  fName = "ceilf" or
+  fName = "ceill" or
+  fName = "floor" or
+  fName = "floorf" or
+  fName = "floorl" or
+  fName = "nearbyint" or
+  fName = "nearbyintf" or
+  fName = "nearbyintl" or
+  fName = "rint" or
+  fName = "rintf" or
+  fName = "rintl" or
+  fName = "round" or
+  fName = "roundf" or
+  fName = "roundl" or
+  fName = "trunc" or
+  fName = "truncf" or
+  fName = "truncl"
+}
+
 from FunctionCall c, FloatingPointType t1, IntegralType t2
 where t1 = c.getTarget().getType().getUnderlyingType() and
       t2 = c.getActualType() and
       c.hasImplicitConversion() and
-      not c.getTarget().getName() = "ceil" and
-      not c.getTarget().getName() = "floor" and
-      not c.getTarget().getName() = "round"
+      not whitelist(c.getTarget().getName())
 select c, "Return value of type " + t1.toString() + " is implicitly converted to " + t2.toString() + " here."
diff --git a/cpp/ql/test/query-tests/Likely Bugs/Conversion/LossyFunctionResultCast/ImplicitDowncastFromBitfield.expected b/cpp/ql/test/query-tests/Likely Bugs/Conversion/LossyFunctionResultCast/ImplicitDowncastFromBitfield.expected
@@ -4,5 +4,3 @@
 | test.cpp:40:13:40:21 | call to getDouble | Return value of type double is implicitly converted to int here. |
 | test.cpp:43:6:43:12 | call to getMyLD | Return value of type long double is implicitly converted to bool here. |
 | test.cpp:45:13:45:19 | call to getMyLD | Return value of type long double is implicitly converted to int here. |
-| test.cpp:78:6:78:11 | call to roundf | Return value of type float is implicitly converted to bool here. |
-| test.cpp:80:13:80:18 | call to roundf | Return value of type float is implicitly converted to int here. |
diff --git a/cpp/ql/test/query-tests/Likely Bugs/Conversion/LossyFunctionResultCast/test.cpp b/cpp/ql/test/query-tests/Likely Bugs/Conversion/LossyFunctionResultCast/test.cpp
@@ -75,9 +75,9 @@ void test1()
 
 	// explicit rounding
 
-	if (roundf(getFloat())) // [FALSE POSITIVE]
+	if (roundf(getFloat()))
 	{
-		setPosInt(roundf(getFloat())); // [FALSE POSITIVE]
+		setPosInt(roundf(getFloat()));
 		setPosFloat(roundf(getFloat()));
 	}
 	if (round(getDouble()))

Original file line number	Diff line number	Diff line change
`@@ -75,9 +75,9 @@ void test1()`
`75`	`75`
`76`	`76`	`// explicit rounding`
`77`	`77`
`78`		`- if (roundf(getFloat())) // [FALSE POSITIVE]`
	`78`	`+ if (roundf(getFloat()))`
`79`	`79`	`{`
`80`		`- setPosInt(roundf(getFloat())); // [FALSE POSITIVE]`
	`80`	`+ setPosInt(roundf(getFloat()));`
`81`	`81`	`setPosFloat(roundf(getFloat()));`
`82`	`82`	`}`
`83`	`83`	`if (round(getDouble()))`