Can Global Variable Initialization in C Ignore Dependencies?

Global Initialization Order in C : Ignoring Dependencies

Problem:

In a code snippet provided, the order of global variable initialization appears to ignore dependencies. Specifically, the constructor method of a struct is being called before the struct instance is declared.

Answer:

1. Initialization Order of Globals:

• Global variables in a single translation unit (source file) are initialized in the order in which they are defined.
• However, the initialization order of global variables in different translation units is unspecified.

2. Dependency Ignorace in Initialization:

Yes, the order of initialization of globals ignores dependencies. This means that a global variable may be initialized before another global variable on which it depends.

3. Ensuring Proper Initialization Order:

To ensure that the constructor of Foo is called before initializing dummy, the following steps can be taken:

• Define globalFoo before dummy in the same translation unit.
• Use a static pointer to the global instance. The pointer will be initialized to null before any dynamic initialization occurs.
• In addToGlobal, check if the pointer is null. If it is, then addToGlobal creates the global Foo instance.

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