False positive 'value is always true/false'

[Istvan Eperjesy]

cppcheck seems to incorrectly handle local structs/classes, w.r.t. default initialized members.

See following example:

bool testCppCheck()
{
  struct TestLocalStruct
  {
    bool b {true};
    bool get() const{ return b;} // CppCheck assumes b is always true
  };

  TestLocalStruct s;

  bool b0 = s.get();  // b0 will be true (default initialized value of s.b) 

  s.b = false;
  bool b1 = s.get();  // b1 will be false, but cppcheck says it will be 1

  // cppcheck concludes, in the return statement below, that b0 and b1 
  // are always true and true will be returned.
  // But in fact, false will be returned (always), because b1 is false.
  return b0 && b1;
}

will generate the following cppcheck output (using version 2.14.1):

Checking testCppCheck.cpp ...
testCppCheck.cpp:22:10: style: Return value 'b0' is always true [knownConditionTrueFalse]
  return b0 && b1;
         ^
testCppCheck.cpp:5:13: note: Assignment 'b{true}', assigned value is 1
    bool b {true};
            ^
testCppCheck.cpp:14:18: note: Calling function 'get' returns 1
  bool b0 = s.get();  // b0 will be true (default initialized value of s.b)
                 ^
testCppCheck.cpp:14:18: note: Assignment 'b0=s.get()', assigned value is 1
  bool b0 = s.get();  // b0 will be true (default initialized value of s.b)
                 ^
testCppCheck.cpp:22:10: note: Return value 'b0' is always true
  return b0 && b1;
         ^
testCppCheck.cpp:22:16: style: Return value 'b1' is always true [knownConditionTrueFalse]
  return b0 && b1;
               ^
testCppCheck.cpp:5:13: note: Assignment 'b{true}', assigned value is 1
    bool b {true};
            ^
testCppCheck.cpp:17:18: note: Calling function 'get' returns 1
  bool b1 = s.get();  // b1 will be false, but cppcheck says it will be 1
                 ^
testCppCheck.cpp:17:18: note: Assignment 'b1=s.get()', assigned value is 1
  bool b1 = s.get();  // b1 will be false, but cppcheck says it will be 1
                 ^
testCppCheck.cpp:22:16: note: Return value 'b1' is always true
  return b0 && b1;
               ^

This will not be reported if the member TestLocalStruct::b is defined after method TestLocalStruct::get().

Can this issue be followed up (create a bugreport), if it is not already?

Thanx,
Istvan

[CHR]

Thanks for reporting, ticket is here: https://trac.cppcheck.net/ticket/13208