Easy way find uninitialized member variables

c++ findbugs initialization
user254669 picture user254669 · Jan 20, 2010 · Viewed 40.7k times · Source

I am looking for an easy way to find uninitialized class member variables.

Finding them in either runtime or compile time is OK.

Currently I have a breakpoint in the class constructor and examine the member variables one by one.

Answer

Grumbel picture Grumbel · May 26, 2010

If you use GCC you can use the -Weffc++ flag, which generates a warnings when a variable isn't initialized in the member initialisation list. This:

class Foo
{
  int v;
  Foo() {}
};

Leads to:

$ g++ -c -Weffc++ foo.cpp -o foo.o
foo.cpp: In constructor ‘Foo::Foo()’:
foo.cpp:4: warning: ‘Foo::v’ should be initialized in the member initialization list

One downside is that -Weffc++ will also warn you when a variable has a proper default constructor and initialisation thus wouldn't be necessary. It will also warn you when you initialize a variable in the constructor, but not in the member initialisation list. And it warns on many other C++ style issues, such as missing copy-constructors, so you might need to clean up your code a bit when you want to use -Weffc++ on a regular basis.

There is also a bug that causes it to always give you a warning when using anonymous unions, which you currently can't work around other then switching off the warning, which can be done with:

#pragma GCC diagnostic ignored "-Weffc++"

Overall however I have found -Weffc++ to be incredible useful in catching lots of common C++ mistakes.

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