Parser: don't issue a bounds warning for trailing one-element array access

[ehaas]

Closes #327

[ehaas]

After this change we're down to 19 warnings in sqlite.

2 from overflow due to incorrect sizeof calculations
2 from #328
4 from #325
11 from unreachable code warnings

[Vexu]

This does seem to work with everything I try but it feels a bit odd having it be part of the global state of the Parser. Is there some specific reason why you chose this approach instead of something more confined in checkArrayBounds?

[ehaas]

I'd prefer to do it in checkArrayBounds but I couldn't think of a way to tell if I was dealing with a trailing one-element array field. GCC doesn't seem to do any bounds checking at all; clang will issue a warning if it's a standalone array or non-trailing one-element field, but no warning if it's a trailing one element field.

[Vexu]

Seems to me that if you pass checkArrayBounds the array Result instead of just the type, then you could inline Parser.getNode and move the logic you currently have in fieldAccessExtra there.

[Vexu]

Accidentally pushed unrelated changes to this branch, reverted now.

[InKryption]

Is there/will there be an option to enable a warning for this?

[ehaas]

Is there/will there be an option to enable a warning for this?

I don't think Clang has an option to enable a warning for this (didn't see any here https://clang.llvm.org/docs/DiagnosticsReference.html) so we could create our own. Any suggestions for the name?

[Vexu]

I couldn't find anything either, my suggestion is -Wold-style-flexible-struct default warning with the same message as .array_after.

[ehaas]

Updated to keep the check local to checkArrayBounds, removed bounds checking for zero-element arrays, added a warning for zero-element arrays (at creation time) and added the -Wold-style-flexible-struct warning. I set it to default off since clang doesn't issue that warning by default but I can switch it to warn by default if you want.

[Vexu]

I'm fine with default off but it should be part of all, extra, or pedantic. Whichever you deem best fit.