[2.4.1] False positive: danglingTempReference

[scott snyder]

hi -

This example gives a false positive with cppcheck 2.4.1:

struct Elt
{
  void foo();
};
template <class T>
struct Subset
{
  typedef Elt& Reference;
};
struct Cont
{
  Subset<Elt>::Reference get();
};


void f (Cont* c)
{
  Elt& e = c->get();
  e.foo();
}

$ cppcheck x.cc
Checking x.cc ...
x.cc:19:3: error: Using reference to dangling temporary. [danglingTempReference]
  e.foo();
  ^
x.cc:18:10: note: Assigned to reference.
  Elt& e = c->get();
         ^
x.cc:19:3: note: Using reference to dangling temporary.
  e.foo();
  ^

I can fix this with this change. I don't observe any changes to the
make test results.

diff --git a/lib/symboldatabase.cpp b/lib/symboldatabase.cpp
index 41498ae58..2a827b929 100644
--- a/lib/symboldatabase.cpp
+++ b/lib/symboldatabase.cpp
@@ -2642,7 +2642,10 @@ bool Function::returnsReference(const Function* function,
 bool unknown)
     const Token* start = function->retDef;
     while (Token::Match(start, "const|volatile"))
         start = start->next();
-    if (start->tokAt(1) == defEnd && !start->type() && !start->isStandardType()
)
+    int iat = 1;
+    while (start->tokAt(iat) && start->tokAt(iat)->str() == "::")
+      iat += 2;
+    if (start->tokAt(iat) == defEnd && !start->type() && !start->isStandardType())
         return unknown;
     // TODO: Try to deduce the type of the expression
     if (Token::Match(start, "decltype|typeof"))

[Daniel Marjamäki]

Thanks! I can reproduce.

Somehow the typedef should be handled better. From the --debug output:

12: Subset<Elt> :: Reference get ( ) ;

Since the typedefs are simplified it would have been better if that line said Elt& get ( ) ; instead. I have created https://trac.cppcheck.net/ticket/10239 for that.

I will look at the returnsReference also..

[Daniel Marjamäki]

I made a fix also inspired by your code eacc9e552ebcb0550cbec8f930e5ab72f58285c9