Jan Kiszka <jan.kis...@web.de> writes: > Markus Armbruster wrote: >> Jan Kiszka <jan.kis...@web.de> writes: >> >>> Markus Armbruster wrote: >>>> Jan Kiszka <jan.kis...@web.de> writes: >>>> >>>>> Luiz, >>>>> >>>>> I missed this when the API was first proposed: >>>>> >>>>> cur_mon is scheduled for removal (one day...). It's just an intermediate >>>>> step to convert all users to explicit 'mon' passing. Thus, new APIs >>>>> should not rely it. >>>>> >>>>> I just realized that monitor_cur_is_qmp() does so. It should be >>>>> refactored to monitor_is_qmp(Monitor *mon). And qerror should be enhance >>>>> by a 'mon' argument as well. Callers that aren't passed a 'mon' >>>>> themselves should either be fixed at this chance or could fall back to >>>>> cur_mon for the time being. >>>>> >>>>> So far for the theory - do you see any pitfalls in the existing usage? >>>> I put in the new uses of cur_mon, Luiz "only" ACKed them. >>>> >>>> At any point in the program execution, we have one current monitor, or >>>> none. Passing around the current monitor within monitor code is >>>> workable, if somewhat tedious. But we need it not just in monitor code, >>>> we need it anywhere where we report errors. In other words, pretty much >>>> everywhere. Including places that do not and should not know about the >>>> monitor. Handing a monitor parameter down pretty much every call chain >>>> is beyond tedious, it's impractical. >>> It's a process, but I don't think it's impractical per se. >>> >>>> The code reporting an error generally does not and should not know >>>> anything about *how* the error gets communicated to the user. >>>> Insulating it from that detail is proper separation of concerns, and >>>> global variable cur_mon is my tool to get it. Good software >>>> engineering. Like many powerful tools, global variables should be used >>>> sparingly and with care. I feel this use is well justified. >>>> >>>> Instead of eliminating cur_mon, I'd like it to be hidden within >>>> monitor.c. There are a few uses left outside it. >>> If we start to allow cur_mon for error reporting, there is no reason not >>> to convert monitor_printf back to where it came from. Back then we >>> agreed on the current path. If we now decide to roll back, then let's >>> make it consistently. >> >> Makes sense. >> >>> But we already refactored quite a lot of code for >>> explicit monitor passing... >>> >>> Jan >>> >>> PS: A patch for establishing monitor_is_qmp is in my queue. Holding it >>> back for now until we agreed how to proceed. >> >> monitor_is_qmp() is used only in a few places. The real troublemakers >> are error_report() & friends, and qerror_report(). These are all over >> the place, with more to come. > > Right, therefore we need a quick decision avoid introducing more > [q]error_report users without mon if cur_mon shall not stay.
We still report errors to stderr in many places that are reachable from the monitor, and fixing that will add error_report() calls. qerror_report() replaces error_report() as needed to provide sufficiently specific errors for QMP. Not relevant to the issue at hand, because both error_report() and qerror_report() use cur_mon the same way. > Just noticed: As long as we rely on cur_mon, user_monitor_complete and > qmp_monitor_complete need to establish this context just link the > command callers. Without this error messages and the qmp test use a > wrong monitor. Can they emit errors? If yes, we have a bug. Can you give an example? If no, we may want to set up cur_mon anyway, just for robustness.