eThe The C++ Standard, [stmt.dcl], paragraph 4 [ISO/IEC 14882-2014], states:
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This compliant solution uses the "construct on first use" idiom to resolve the static initialization order issue. The code for file.h and file2.c are unchanged; only the static numWheels in file1.c is moved into the body of a function. Consequently the initialization Consequently, the initialization of numWheels is guaranteed to happen when control flows over the point of declaration, ensuring control over the order. The global object c is initialized before execution of main() begins, so by the time get_num_wheels() is called, c is guaranteed to have already been dynamically initialized.
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