When Are C Static Class Members Initialized?

Timing of Static Class Member Initialization in C

Determining when static class members in C are initialized can be a complex matter. However, there are certain assumptions that can guide developers in understanding the timing of such initialization.

The C Standard (3.6.2) provides two crucial guarantees regarding static initialization:

1. Ordered Initialization: Objects with static storage duration defined in the same translation unit (typically a .cpp file) are initialized in the order of their definitions, not their declarations.
2. Initialization Before Use: Static initialization of objects within a translation unit is guaranteed to complete before any object or function from that unit is used.

While these guarantees establish a general framework, it's important to note that:

• Intra-unit Ordering: The exact order of initialization for objects defined in a single translation unit is implementation-dependent.
• Inter-unit Ordering: The order of initialization for objects defined in different translation units is not specified by the Standard.

However, as a rule of thumb, if no static initializers rely on other static initializers, then accessing static members should not raise any concerns regarding initialization order.

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