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[Python-Dev] Use C extensions compiled in release mode on a Python compiled in debug mode

Antoine Pitrou solipsis at pitrou.net
Wed Apr 24 10:03:22 EDT 2019 
On Wed, 24 Apr 2019 01:44:17 +0200
Victor Stinner <vstinner at redhat.com> wrote:
> 
> The first requirement for the use case is that a Python debug build
> supports the ABI of a release build. The current blocker issue is that
> the Py_DEBUG define imply the Py_TRACE_REFS define: PyObject gets 2
> extra fields (_ob_prev and _ob_next) which change the offset of all
> attributes of all objects and makes the ABI completely incompatible. I
> propose to no longer imply Py_TRACE_REFS *by default* (but keep the
> code):
> 
> https://bugs.python.org/issue36465
> https://github.com/python/cpython/pull/12615

+1 from me.

> The second issue is that library filenames are different for a debug
> build: SOABI gets an additional "d" flag for Py_DEBUG. A debug build
> should first look for "NAME.cpython-38dm.so" (flags: "dm"), but then
> also look for "NAME.cpython-38m.so" (flags: "m").

Sounds fair (but only on Unix, I guess).

> Maybe pip could be enhanced to support installing C extensions
> compiled in release mode when using a debug mode. But that's more for
> convenience, it's not really required, since it is easy to switch the
> Python runtime between release and debug build.

Not sure what you mean by "easy to switch the Python runtime".  As soon
as I want to use pip, I have to use a release build, right?

Regards

Antoine.
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