[issue30104] clang 4.0 miscompiles dtoa.c, giving broken float parsing and printing

Change by Eitan Adler : -- nosy: +eitan.adler ___ Python tracker ___ ___

[issue30104] clang 4.0 miscompiles dtoa.c, giving broken float parsing and printing

STINNER Victor added the comment: dtoa.c is now compiled with -fno-string-aliasing (for any clang version, not only clang 4.0) on Python 3.5, 3.6 and 3.7. It was decided to not touch dtoa.c to not diverge from upstream. Thanks Dimitry Andric and Mark Dickinson for your reviews and support in

[issue30104] clang 4.0 miscompiles dtoa.c, giving broken float parsing and printing

STINNER Victor added the comment: New changeset 03a7ab77d2f75323e1f3e8b6a1c164e701d58bfb by Victor Stinner in branch '3.5': bpo-30104: Use -fno-strict-aliasing on clang (#1376) (#1377) https://github.com/python/cpython/commit/03a7ab77d2f75323e1f3e8b6a1c164e701d58bfb --

[issue30104] clang 4.0 miscompiles dtoa.c, giving broken float parsing and printing

Changes by STINNER Victor : -- pull_requests: +1485 ___ Python tracker ___ ___

[issue30104] clang 4.0 miscompiles dtoa.c, giving broken float parsing and printing

STINNER Victor added the comment: New changeset 809101f14f27ddb394cd77c477470761ecf99f41 by Victor Stinner in branch '3.6': bpo-30104: Use -fno-strict-aliasing on clang (#1376) https://github.com/python/cpython/commit/809101f14f27ddb394cd77c477470761ecf99f41 --

[issue30104] clang 4.0 miscompiles dtoa.c, giving broken float parsing and printing

Changes by STINNER Victor : -- pull_requests: +1484 ___ Python tracker ___ ___

[issue30104] clang 4.0 miscompiles dtoa.c, giving broken float parsing and printing

STINNER Victor added the comment: New changeset 826f83f1d562a7b878499bc3af2267cfdfe5f2f9 by Victor Stinner in branch 'master': bpo-30104: Only use -fno-strict-aliasing on dtoa.c (#1340) https://github.com/python/cpython/commit/826f83f1d562a7b878499bc3af2267cfdfe5f2f9 --

[issue30104] clang 4.0 miscompiles dtoa.c, giving broken float parsing and printing

STINNER Victor added the comment: I would like to fix FreeBSD CURRENT buildbots of Python 2.7, 3.5 and 3.6, so here my attempt to restrict the -fno-strict-aliasing option to the dtoa.c file: https://github.com/python/cpython/pull/1340 I chose to add the flag for any C compiler. If you think

[issue30104] clang 4.0 miscompiles dtoa.c, giving broken float parsing and printing

Changes by STINNER Victor : -- pull_requests: +1451 ___ Python tracker ___ ___

[issue30104] clang 4.0 miscompiles dtoa.c, giving broken float parsing and printing

STINNER Victor added the comment: > I also note that -fno-strict-aliasing is being included in 2.7's compile > arguments Ah right, PyObject structures of Python 2 doesn't respect strict aliasing... -- ___ Python tracker

[issue30104] clang 4.0 miscompiles dtoa.c, giving broken float parsing and printing

Kubilay Kocak added the comment: 2.7 branch on koobs-freebsd-current worker doesn't appear to be failing currently, but there may be differences in (or a lack of equivalent) coverage compared to 3.*. I also note that -fno-strict-aliasing is being included in 2.7's compile arguments: cc

[issue30104] clang 4.0 miscompiles dtoa.c, giving broken float parsing and printing

STINNER Victor added the comment: > This appears to require backporting to 3.6 and 3.5 which are also failing: I'm aware of that and I plan to fix these versions as well (2.7 also, no?), but I would like to first decide if we "fix" dtoa.c aliasing, or if we restrict -fno-strict-aliasing flag

[issue30104] clang 4.0 miscompiles dtoa.c, giving broken float parsing and printing

Changes by Kubilay Kocak : -- stage: -> backport needed type: -> behavior ___ Python tracker ___

[issue30104] clang 4.0 miscompiles dtoa.c, giving broken float parsing and printing

Kubilay Kocak added the comment: Thank you for investigating Victor. This appears to require backporting to 3.6 and 3.5 which are also failing: FAIL: test_repr (test.test_float.ReprTestCase) -- Traceback (most recent call

[issue30104] clang 4.0 miscompiles dtoa.c, giving broken float parsing and printing

STINNER Victor added the comment: Ok, the FreeBSD CURRENT buildbot is repaired: "AMD64 FreeBSD CURRENT Debug 3.x is complete: Success". -- ___ Python tracker

[issue30104] clang 4.0 miscompiles dtoa.c, giving broken float parsing and printing

STINNER Victor added the comment: New changeset 35f3d240ee5f0958034bd500949b08764e36f4dc by Victor Stinner in branch 'master': bpo-30104: configure now detects when cc is clang (#1233) https://github.com/python/cpython/commit/35f3d240ee5f0958034bd500949b08764e36f4dc --

[issue30104] clang 4.0 miscompiles dtoa.c, giving broken float parsing and printing

STINNER Victor added the comment: Oh... I only tested my configure patch on Linux using ./configure CC=clang, but the change has no effect on FreeBSD where $CC is /usr/bin/cc and so my code doesn't detect clang correctly. I proposed https://github.com/python/cpython/pull/1233 which runs "cc

[issue30104] clang 4.0 miscompiles dtoa.c, giving broken float parsing and printing

Changes by STINNER Victor : -- pull_requests: +1351 ___ Python tracker ___ ___

[issue30104] clang 4.0 miscompiles dtoa.c, giving broken float parsing and printing

Changes by Eric V. Smith : -- nosy: +eric.smith ___ Python tracker ___ ___

[issue30104] clang 4.0 miscompiles dtoa.c, giving broken float parsing and printing

Mark Dickinson added the comment: FWIW, I can confirm that adding `-fno-strict-aliasing` fixes all failing float-related tests on OS X. -- ___ Python tracker

[issue30104] clang 4.0 miscompiles dtoa.c, giving broken float parsing and printing

STINNER Victor added the comment: Mark: "I seem the same issues on OS X (10.9.5) when compiling with clang 4.0 from MacPorts. So this doesn't seem to be FreeBSD-specific." I confirm, I reproduced the bug on Linux using Clang 4.0. Mark: "But if that's what we have to do to maintain correctness

[issue30104] clang 4.0 miscompiles dtoa.c, giving broken float parsing and printing

STINNER Victor added the comment: New changeset 28205b203a4742c40080b4a2b4b2dcd800716edc by Victor Stinner in branch 'master': bpo-30104: Use -fno-strict-aliasing on clang (#1221) https://github.com/python/cpython/commit/28205b203a4742c40080b4a2b4b2dcd800716edc --

[issue30104] clang 4.0 miscompiles dtoa.c, giving broken float parsing and printing

Changes by Mark Dickinson : -- components: +Build ___ Python tracker ___ ___

[issue30104] clang 4.0 miscompiles dtoa.c, giving broken float parsing and printing

Mark Dickinson added the comment: I seem the same issues on OS X (10.9.5) when compiling with clang 4.0 from MacPorts. So this doesn't seem to be FreeBSD-specific. Changing title and raising priority: failure for repr (and marshal, JSON, etc.) to roundtrip seems like a critical breakage to