What is the meaning of prepended double colon “::”?

Question

I found this line of a code in a class which I have to modify:

::Configuration * tmpCo = m_configurationDB;//pointer to current db

and I do

Answer 1

:: is used to link something ( a variable, a function, a class, a typedef etc...) to a namespace, or to a class.

if there is no left hand side before ::, then it underlines the fact you are using the global namespace.

e.g.:

::doMyGlobalFunction();