gh-82616: Add Py_IS_TYPE_SIGNED() macro

[vstinner]

_posixsubprocess: add a static assertion to ensure that the pid_t
type is signed.

Replace _Py_IntegralTypeSigned() with Py_IS_TYPE_SIGNED().

[vstinner]

cc @serhiy-storchaka @erlend-aasland @corona10

[serhiy-storchaka]

I did not know about _Py_IntegralTypeSigned(). It could be used in Modules/posixmodule.c and other interfaces to OS.

But I hesitate about adding it to the public API. Compilers can complain about "always true/false" condition. And what to do with this in PyPy and bindings in other programming languages?

[serhiy-storchaka]

I did not know about _Py_IntegralTypeSigned(). It could be used in Modules/posixmodule.c and other interfaces to OS.

But I hesitate about adding it to the public API. Compilers can complain about "always true/false" condition. And what to do with this in PyPy and bindings in other programming languages?

[vstinner]

Ok, I add it as a private macro instead.

[vstinner]

Oh, the Ubtuntu job logs a compiler warning:

comparison of unsigned expression < 0 is always false [-Wtype-limits]

[erlend-aasland]

Neat trick to get rid of the compiler warning! LGTM, but I'd run it through the buildbots one more time before merging.

[bedevere-bot]

🤖 New build scheduled with the buildbot fleet by @vstinner for commit 786c514 🤖

If you want to schedule another build, you need to add the ":hammer: test-with-buildbots" label again.

[vstinner]

buildbot/PPC64 Fedora PR — Build done.

Unrelated error: ../configure: line 2692: cannot create temp file for here-document: No space left on device

[vstinner]

Merged, thanks for the reviews.