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[wg14/wg21 liaison] C and C++ Compatibility Dec Agenda

From: Aaron Ballman <compatibility.sg.chair_at_[hidden]>
Date: Tue, 30 Nov 2021 13:10:52 -0500
Our next meeting will be on Thur Dec 9, 2021 at 18:00 UTC

You can join the meeting at https://iso.zoom.us/j/5513145100

**NEW PASSWORD: same as the old one, but spelled as a C reserved
identifier instead of a C++ keyword; contact Aaron Ballman if you have
questions **

We will be discussing the following papers:

WG14 N2808 (http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2808.htm)
Allow 16-bit ptrdiff_t again
Proposes changing the current minimum size for ptrdiff_t from 17 bits
down to 16 bits on both hosted and freestanding implementations. This
proposal was provisionally adopted for C23 and the author is
especially interested in feedback about blocking implementation or
compatibility concerns that WG14 should be aware of before formally
adopting the feature.

P2460 (https://wg21.link/P2460R0) Relax requirements on wchar_t to
match existing practices
Proposes to remove the constraint as to which encoding is associated
with wchar_t, as is commonly done in existing practice. The author
believes this should not have significant impact on cross-language
compatibility as it is relaxing a constraint, but is interested in
feedback confirming or refuting that belief.

P1494R2 (https://wg21.link/p1494r2) Partial program correctness
This paper proposes restricting "time-travel optimizations" with
"execution epochs" that have independent guarantees about their
observable behavior in the absence of undefined behavior. The proposal
introduces a new library facility (requiring compiler magic) to
specify the boundaries of these epochs. Examples, some of them of use
with contracts, are provided. The author is looking for information
about interest in the direction in the C community (which shares the
execution model) as well as implementation or compatibility concerns.



Received on 2021-11-30 12:11:09