问题
I know that if a char array is a global or a static local, its elements get initialized to \0's, but what if the char array is an extern variable?
回答1:
If the variable was declared as extern but is nonglobal, it too receives the same initialization handling. For instance
namespace A { extern int x; int x;}
This nonglobal variable will be initialized to zero. All namespace scope variables receive this handling.
回答2:
An extern variable is just a declaration. The variable is initialized in the module that defined it. Since in that module the variable is a global, it gets zero-initialized.
回答3:
extern is only a declaration.
Whether the variable will be initialized depends on the definition.
Also, the value of the variable will depend on type of initialization. The C++ standard defines 3 types of initialization:
- Zero-initialize
- Default-Initialize
- Value-Initialize
C++03 Standard 8.5/5 aptly defines each.
Good Read:
What is the difference between a definition and a declaration?
回答4:
The extern keyword only declares that the variable exists, it does not define its value.
because of global scope it initialised to 0
来源：https://stackoverflow.com/questions/13660085/are-extern-variables-initialized-to-their-default-value