On 2013.01.12 03:23, Jie Zhang wrote: > But this warning is introduced by libusb, not by user
Not really. The warning is introduced by the compiler as a result of libusbx using zero sized arrays, which may *or may not* be OK with regards to what the user is planning to do, to which we have no insight on. > so we should > hide from user. And we know this piece of code is safe, so we can > disable the warning. I disagree. We have no way of "knowing" that the code is 100% safe. The only thing we are assuming is that the using zero-sized arrays should be OK when compiling our library using the MSVC compilers we support, and therefore we disable the warning there. "Knowing" that zero-sized arrays will be 100% safe when used with code that we didn't write ourselves, and MSVC compilers that aren't under our control, is something that we would need to prove, which I don't think you or anyone can do. So, to reiterate what I was trying to say earlier, the Microsoft engineers did put a warning when zero-sized arrays are in use for a reason, most likely because they have experienced situations where zero-sized arrays resulted in issues that developers would need to be alerted on. While we have some idea, we do not know precisely what these reasons were, therefore I don't think it is safe for us, who didn't build the compiler, to assume that for code that isn't under our control, those warnings are benign and can safely be ignored. >> I will assume that the warning is there for a legitimate reason and >> therefore that some libusbx users do want to be alerted for a >> nonstandard extension used. I think I can see a scenario for it if >> they're going to interop with a library or app where 1 sized arrays were >> used instead of zero sized arrays, in which case they may get very bad >> surprises when using sizeof on the structs they going to interchange, >> whereas this is probably what the warning is meant to alert against. >> > Sorry, I don't understand this part. I'm just trying to provide an example where someone might be putting a library that was compiled with nonstandard C extensions (libusbx) and an application or library that uses a stricter C standard together. Most likely compilation should fail when libusb.h is parsed, but it may not, and if that user, is using equivalent structures that use 1 sized arrays rather than zero sized arrays, in order to comply with a more stringent C standard, when they try to interchange their 1 sized arrays based structs with libusbx's zero sized ones, they may encounter issues. > libusb.h is a public header, so this is not an internal affair. I agree with that. As such, I would state that our goal is to make sure that libusbx users are alerted to potential issues. > As I said above, this piece of code is safe. Can you prove it? If you state that the code is safe, then you must be able to demonstrate that every single Microsoft compiler a libusbx application can be compiled with, and every kind of libusbx application one can think of, will not have an issue with zero sized arrays, ever. Personally, I don't believe you or anyone can do that, which is why I will continue to advise caution. > We don't need this warning to > warn user. As you said, this piece of code is directly under out > control, so we have the responsibility to take care of the warning for > user. Not really, what I tried to say is that the libusbx library code is under our control, and only that code. But libusbx, and the libusb.h header, are meant to be used in applications and with code that are not under our control at all, and who might be using our structures in way we haven't anticipated. As such, my opinion is that we should not risk silencing that warning, in case we are wrong and it does serve a legitimate purpose that we simply haven't foreseen yet, due to lack of experience or imagination. I wish I could have your confidence in stating that "the zero sized arrays used in the libusb.h header are never going to be an issue with MS compilers", but to me that's akin to predicting the future, which is a bit too much of a stretch. Finally, I also fail to see why disabling this warning should be that much of a priority. It's not like we're preventing anyone to disable it should they choose so, and it shouldn't take an experienced developer more than 30 seconds to do just that in their application. Regards, /Pete ------------------------------------------------------------------------------ Master Visual Studio, SharePoint, SQL, ASP.NET, C# 2012, HTML5, CSS, MVC, Windows 8 Apps, JavaScript and much more. Keep your skills current with LearnDevNow - 3,200 step-by-step video tutorials by Microsoft MVPs and experts. SALE $99.99 this month only -- learn more at: http://p.sf.net/sfu/learnmore_122912 _______________________________________________ libusbx-devel mailing list libusbx-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/libusbx-devel
