What would be an inherently constrained API, then? I've successfully managed to create circular dependencies in quite a few different styles, so I'd love to find one that saves me from myself ;)
typedef enum {
CONSOLE_LOGGER,
DATABASE_LOGGER,
/* etc. */
} LoggerType;
void add_logger(LoggerType);
In this API you're constrained by what loggers you can add. It's not the totally unchecked free-for-all that a callback-based API provides. The user is strictly unable to shoot themselves in the foot.But this limits the expressive power that callbacks provide. Sorry I don't have any other API recommendations. The only way I can think of to stay expressive while safeguarding against unintended abuse is to include code analysis.