vsprintf_s() should return 0 for "vsprintf_s: len exceeds dmax"

[Juno-Explorer]

According to standard:
If no runtime-constraint violation occurred, the vsprintf_s function returns the number of characters written in the array, not counting the terminating null character. If an encoding error occurred, vsprintf_s returns a negative value. If any other runtime-constraint violation occurred, vsprintf_s returns zero.

Scenario "vsprintf_s: len exceeds dmax" is run-time constraint violation & not encoding error so the return value should be 0.

Link to the code instance: https://github.com/rurban/safeclib/blob/master/src/str/vsprintf_s.c#L147

[rurban]

Yes, but in this case I (and all others) think the standard made an error. I'll have to check the history of that.
All existing implementations do return -1, all similar functions do return -1.

The revision and rationale for this change is: http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1141.pdf
keeping count += sprintf(buf + count, format_string, args); valid, when no encoding errors can occur.
google site:www.open-std.org vsprintf_s

I'll add a doc note that the spec is most likely wrong on this one, and keep the -1.
Even the author of this change itself, Microsoft, later changed its decision, and reverted back to -1.

[rurban]

Done with 345101c and 76bfbf3

When all other deviate from C11 and C11 is wrong so do we.