Fun fact: naming identifiers with leading underscores in C conflicts with reserved use and should always be avoided. I noticed Gobee declares double-underscores liberally.

Per 6.4.3 (Identifiers) of C23 (ISO/IEC 9899:202y N3886):

  — All identifiers that begin with a double underscore (__) or begin with an underscore (_) followed by an uppercase letter are reserved for any use, except those identifiers which are lexically identical to keywords.
  — All identifiers that begin with an underscore are reserved for use as identifiers with file scope in both the ordinary and tag name spaces.

And per 7.1.3 (Reserved identifiers) of C11 (ISO/IEC 9899:201x N1570):

  — All identifiers that begin with an underscore and either an uppercase letter or another underscore are always reserved for any use.