alt Hacker NewsBecause it imagines that no library other than libc has an ABI that depends on intmax_t.
Suppose I have a libfoo that has a public function that takes an intmax_t parameter. Or that has a public struct with an intmax_t field. It will be compiled for a particular definition of intmax_t. If you try to link it with a program that uses a different definition, it will fail.
The article's solution with the "MY_LIBC_NEW_CODE" define cannot work because no existing C code knows about "MY_LIBC_NEW_CODE".
The proposed mechanism is somewhat useful to a library that wants to provide multiple incompatible implementations of a function. (But this is mostly only interesting for libc implementations that need to handle historic incompatibilities between all the various Unix specs. Other libraries can just give their new, incompatible function a new name.) It's useless if you want to make an incompatible change to a type definition.
> Because it imagines that no library other than libc has an ABI that depends on intmax_t.
I don't get quite the same impression. The sense I get is more that such a change would basically need to happen "bottom-up":
> Some of [the scenarios that aren't fixed by this proposal] are just the normal dependency management issues. If you build a library on top of something else that uses one of the changed types (such as intmax_t or something else), then you can’t really upgrade until your dependents do.
> <snip>
> For those of us in large ecosystems who have to write plugins or play nice with other applications and system libraries, we’re generally the last to get the benefits.
In which case the benefit of the proposal (as far as I understand) is that such bottom-up changes can occur without forcibly breaking other consumers.