[python-committers] Py_UNREACHABLE

[Victor Stinner]

The good news is that other C macros are now documented as well!

https://docs.python.org/dev/c-api/intro.html#useful-macros

If you look at Include/pymacro.h there are even more crazy macros
which are not documented yet, like Py_BUILD_ASSERT().

I like Py_ARRAY_LENGTH() which gives the length of an array and not
its size in bytes. The macro is nice because it fails with a
compilation error if the argument is not an array! For example, it
fails on "char *not_an_array" or "char not_an_array_neither[];".

Victor

2017-09-15 20:59 GMT+02:00 Barry Warsaw <barry at python.org>:
> I landed bpo-31338 / PR #3374 which adds a Py_UNREACHABLE() macro to master, along with some additional documentation in the C API describing this and a few other common macros.  If you’re writing or reviewing C changes that include unreachable code paths, please use this macro for consistency, instead of other approaches like assert() (which can be compiled out) and `return NULL`, etc.
>
> As part of the PR, I changed a bunch of existing instances in the code:
>
> https://github.com/python/cpython/pull/3374/files
>
> If you find any cases I’ve missed, feel free to submit a PR and I will happily review it.  I think this makes our code more consistent and ultimately safer.
>
> (Thanks Victor for the PR review!)
>
> Cheers,
> -Barry
>
>
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