How does NV_FUNCT differ from NV_FUNCTION?

[krader1961]

Please explain to me the difference between NV_FUNCT in src/cmd/ksh93/include/nval.h and NV_FUNCTION in src/cmd/ksh93/include/name.h. It seems to me that everyplace that uses NV_FUNCT should be using NV_FUNCTION. Other than the definition of NV_FUNCTION which should be using NV_MISC (formerly NV_IDENT). This is another instance where symbols like NV_FUNCTION should be a distinct bit rather than a composite bit field. And the NV_ symbols in name.h should be in nval.h. See issue #1038.

I continue to be amazed that this code works as well as it does given such ambiguities that have already been shown to be the source of bugs.

[krader1961]

Please notice that expressions like this from src/cmd/ksh93/sh/name.c are fundamentally broken:

nv_isattr(np, NV_ARRAY | NV_INTEGER | NV_FUNCT | NV_REF)

That's because they can result in false positives if any of those symbols are defined in terms or more than a single bit. Which isn't true of that specific expression. However, note that NV_FUNCT, and some of the other symbols, are used in a multi-bit definition of a different symbol. And thus might be set as a side-effect of setting one of those other symbols. Furthermore, some of those symbols, such as NV_FUNCT, are defined defined in terms of a different namval attr bit. In this case NV_FUNCT is an alias for NV_IDENT which is now defined as an alias for NV_MISC. The latter being used for many other purposes.

This is related to #855. And this also probably accounts for some of the use-after-free and similar failures that are found when running the code under a debug malloc, ASAN, or valgrind.