c-vsemi-status-unknown-p-fn is a variable defined in `cc-engine.el'.
Its value is

  • Automatically becomes buffer-local when set.

Contains a function "are we unsure whether there is a virtual semicolon on this line?".
The (admittedly kludgy) purpose of such a function is to prevent an infinite
recursion in c-beginning-of-statement-1 when point starts at a `while' token.
The function MUST NOT UNDER ANY CIRCUMSTANCES call c-beginning-of-statement-1,
even indirectly. This variable contains nil for languages which don't have
EOL terminated statements.