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
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@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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On Sep 15, 2017, at 12:36, Victor Stinner victor.stinner@gmail.com wrote:
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[];".
PRs anyone? :)
-Barry
participants (2)
-
Barry Warsaw -
Victor Stinner