Function libexpr_init 

pub unsafe extern "C" fn libexpr_init(context: *mut c_context) -> err

@brief Initialize the Nix language evaluator. @ingroup libexpr_init

This function must be called at least once, at some point before constructing a EvalState for the first time. This function can be called multiple times, and is idempotent.

@param[out] context Optional, stores error information @return NIX_OK if the initialization was successful, an error code otherwise.