What Guarantees Exist Regarding the Initialization Order of Static C Class Members?

Initialization of Static C Class Members

In C , it can be challenging to determine when static class members are initialized. However, some safe assumptions can be made.

Guaranteed Initialization Order Within a Translation Unit

The C standard specifies that for objects defined in the same translation unit:

• Their storage is zero-initialized before any other initialization.
• Objects with static storage duration initialized with constant expressions are initialized before dynamic initialization.
• Objects defined in namespace scope are initialized in the order of their definition.

Initialization Before Use

Secondly, the standard guarantees that the initialization of static objects in a translation unit will be completed before any object or function from that unit is used.

Example

Based on these principles, assume the following code:

struct A {
  static int x;
};

struct B {
  static int y;
};

int main() {
  return A::x + B::y;
}

In this case, you can safely assume that the initialization of A::x and B::y will occur before main() is called. This allows you to safely access these static variables within main(). However, note that the order of initialization between A::x and B::y is implementation-defined and may not be consistent across different compilers or architectures.

The above is the detailed content of What Guarantees Exist Regarding the Initialization Order of Static C Class Members?. For more information, please follow other related articles on the PHP Chinese website!