C++: Fix another implicit/explicit this FP

Author: d10c

cpp/ql/src/Best Practices/Likely Errors/CommaBeforeMisleadingIndentation.ql

@@ -11,12 +11,35 @@
 import cpp
 import semmle.code.cpp.commons.Exclusions
 
+/**
+ * Holds if this is an implicit `this`.
+ *
+ * ThisExpr.isCompilerGenerated() is currently not being extracted, so use a heuristic.
+ */
+predicate isCompilerGenerated(ThisExpr te) {
+  exists(
+    string filepath, int line, int colStart, int colEnd, boolean zeroDiff, boolean sameLocAsCall
+  |
+    te.getLocation().hasLocationInfo(filepath, line, colStart, line, colEnd) and
+    (if colStart = colEnd then zeroDiff = true else zeroDiff = false) and
+    (
+      if exists(Call c | c.getQualifier() = te | c.getLocation() = te.getLocation())
+      then sameLocAsCall = true
+      else sameLocAsCall = false
+    )
+  |
+    zeroDiff = true
+    or
+    zeroDiff = false and sameLocAsCall = true
+  )
+}
+
 /** Gets the sub-expression of 'e' with the earliest-starting Location */
 Expr normalizeExpr(Expr e) {
-  if forex(Expr q | q = e.(Call).getQualifier() | not q.(ThisExpr).isCompilerGenerated())
+  if forex(Expr q | q = e.(Call).getQualifier() | not isCompilerGenerated(q.(ThisExpr)))
   then result = normalizeExpr(e.(Call).getQualifier())
   else
-    if forex(Expr q | q = e.(FieldAccess).getQualifier() | not q.(ThisExpr).isCompilerGenerated())
+    if forex(Expr q | q = e.(FieldAccess).getQualifier() | not isCompilerGenerated(q.(ThisExpr)))
     then result = normalizeExpr(e.(FieldAccess).getQualifier())
     else
       if e.hasExplicitConversion()

cpp/ql/test/query-tests/Best Practices/Likely Errors/CommaBeforeMisleadingIndentation/test.cpp

@@ -16,7 +16,7 @@ struct X {
 #define BAZ //printf
 
 struct Foo {
-	int i;
+	int i, i_array[3];
 	int j;
 	virtual int foo(int) = 0;
 	virtual int bar(int, int) = 0;
@@ -27,9 +27,9 @@ struct Foo {
 			void tutu() {}
 			long toto() { return 42; }
 		} titi;
-	} *tata;
 
-	Tata::Titi **titi_ptr_ptr;
+		Titi *operator->() { return &titi; }
+	} *tata;
 };
 
 int Foo::test(int (*baz)(int))
@@ -38,7 +38,7 @@ int Foo::test(int (*baz)(int))
 
 	if (i)
 		(void)i,	// GOOD
-		(void)j;
+		j++;
 
 	if (i)
 		this->foo(i),	// GOOD
@@ -181,8 +181,8 @@ int Foo::test(int (*baz)(int))
       (tata->titi.tutu(),
        foo(tata->titi.toto())); // GOOD
 
-	(*titi_ptr_ptr)->tutu(), // GOOD
-	(&i)[0] += (int)(*titi_ptr_ptr)->toto();
+	(*tata)->toto(), // GOOD
+	i_array[i] += (int)(*tata)->toto();
 
 	return quux;
 }