In C++ classes/structs are identical (in terms of initialization).
A non POD struct may as well have a constructor so it can initialize members.
If your struct is a POD then you can use an initializer.
struct C
{
int x;
int y;
};
C c = {0}; // Zero initialize POD
Alternatively you can use the default constructor.
C c = C(); // Zero initialize using default constructor
C c{}; // Latest versions accept this syntax.
C* c = new C(); // Zero initialize a dynamically allocated object.
// Note the difference between the above and the initialize version of the constructor.
// Note: All above comments apply to POD structures.
C c; // members are random
C* c = new C; // members are random (more officially undefined).
I believe valgrind is complaining because that is how C++ used to work. (I am not exactly sure when C++ was upgraded with the zero initialization default construction). Your best bet is to add a constructor that initializes the object (structs are allowed constructors).
As a side note:
A lot of beginners try to value init:
C c(); // Unfortunately this is not a variable declaration.
C c{}; // This syntax was added to overcome this confusion.
// The correct way to do this is:
C c = C();
A quick search for the "Most Vexing Parse" will provide a better explanation than I can.