Gamedev forum software crapped its pants again, so can not use any formatting. Did my best to make it readable.
frob: "4201 is valid unless you told the compiler to use c++11."
VC++ does not have such a specific switch - all that it is capable of supporting is enabled by default. And i use a lot of c++11 features. One might say that vc++ is not really c11 - but that is not an useful distinction as it tries to be everywhere else.
frob: "The invalid automatic functions are correct, these are not things the compiler can automatically generate."
_Nor does it need to_. The warning is a very low priority bug in the compiler: http://connect.microsoft.com/VisualStudio/feedback/details/488660/improper-issuance-of-c4610
Even so, it is still an useless warning as the language does not allow improper use anyway (ie. more than it normally does) - there is nothing worth warning about.
And yes, one should generally avoid such structures. Exceptions excepted (funny: commented out the warning to see where i use them => apparently i do not use them at all anymore [except a few of the assignment ones - adding "=delete" assignments]).
frob: "4100 is a fun one that requires an understanding of the language history."
Interesting. I did not know that backstory. Thanks.
frob: "The 4310 case is VERY valid in this case. int16(0x8000) is an overflow"
Exactly. Which is why it is tagged "UNHELPFUL" instead of "BOGUS" or "USELESS". Unhelpful is a fairly subjective tag (*).
I use, in every language, hex-notation to signify bit-patterns. Ie. "int16(0x8000)" should be interpreted as bit-pattern 0x8000 in int16 storage (_ie. platform dependently interpreted as some 16 bit integer_). Obviously, C does not interpret it that way and never will - not a problem here.
The warning is very rare.
I have only a few of them from various macro-driven tests. Platform specific integer conversion ... the only place where anyone would write stuff like "int16(0x8000)". Hm, i should move the pragma there and undo it after the test section - much more sane. Thanks.
(*) I copy pasted thous few example lines out - leaving out some less likely useful ones (and commented out unused ones) and a few comments. One of them probably bited here. Pragma reminder-comment in split with "//": left of it is about the warning - to the right is for use-case reminders of how one might get the warning etc. So, BOGUS for "int16(0x8000)" does not mean the warning is bogus! - it signifies that it is UNHELPFUL as it is BOGUS for the use-case (the bit pattern fits nicely).
Perhaps i should have left out all the UNHELPFUL tagged ones here due of their high subjectivity.