| msg245879 - (view) |
Author: Andrew Turner (Andrew Turner) |
Date: 2015-06-27 15:08 |
| The attached patch moves to use the fenv functions on FreeBSD to control the floating-point environment. This will be needed as I don't expect FreeBSD will have these functions on arm64. I would expect a similar change should be applied to any supported development branch. |
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| msg251221 - (view) |
Author: STINNER Victor (vstinner) *  |
Date: 2015-09-21 12:12 |
| It looks like fpsetmask() was deprecated since many years, and that fedisableexcept() is available since FreeBSD 5.3. Since we try to support FreeBSD 9, it's fine to drop support of FreeBSD < 5.3. I'm concerned by the "CAVEATS" section below. Should we put "#pragma STDC FENV_ACCESS ON" in all .c file using a C double? @skrah: I saw this pragma in Modules/_decimal/libmpdec/mpdecimal.c. Any idea if applying this patch is fine? Maybe we can start by applying it to the default branch? If this patch is required to support arm64, I think that it's ok to apply it to 2.7, 3.4 and 3.5 since we still accept changes to fix platform compatibility issues. http://www.unix.com/man-page/freebsd/3/fpsetmask/ --- DESCRIPTION The routines described herein are deprecated. New code should use the functionality provided by fenv(3). --- http://www.unix.com/man-page/freebsd/3/fenv/ --- HISTORY The <fenv.h> header first appeared in FreeBSD 5.3. It supersedes the non-standard routines defined in <ieeefp.h> and documented in fpgetround(3). CAVEATS The FENV_ACCESS pragma can be enabled with #pragma STDC FENV_ACCESS ON --- |
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| msg251227 - (view) |
Author: Stefan Krah (skrah) * |
Date: 2015-09-21 14:42 |
| In theory we should set FENV_ACCESS whenever the control word is changed (C99): "If part of a program tests floating-point status flags, sets floating-point control modes, or runs under non-default mode settings, but was translated with the state for the FENV_ACCESS pragma "off", the behavior is undefined." In practice gcc ignores the pragma, icc and cl.exe use it, not sure about clang. |
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| msg251228 - (view) |
Author: STINNER Victor (vstinner) * |
Date: 2015-09-21 14:53 |
| FYI in Python/pytime.c, I put a lot of "volatile double" when tests started to fail on some platforms. It's inefficient, but it's easier than teaching how to disable optimizations on each different compiler :-p |
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| msg251230 - (view) |
Author: Stefan Krah (skrah) * |
Date: 2015-09-21 14:58 |
| Ok, clang does not support it either: https://llvm.org/bugs/show_bug.cgi?id=10409 |
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| msg251231 - (view) |
Author: Stefan Krah (skrah) * |
Date: 2015-09-21 15:20 |
| Regarding volatile: gcc/clang seem to honor *some* changes to the control word. At least in libmpdec both compilers have always left the settings 80bit-prec/ROUND_CHOP intact, even though it's not the default. Let's rewrite Python in asm to avoid these issues. :) |
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| msg251258 - (view) |
Author: STINNER Victor (vstinner) * |
Date: 2015-09-21 20:48 |
| Sorry, I don't understand if we should apply or not the patch :-/ |
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| msg257429 - (view) |
Author: Andrew Turner (Andrew Turner) |
Date: 2016-01-03 21:49 |
| Can this be applied? |
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| msg258690 - (view) |
Author: Kubilay Kocak (koobs)  |
Date: 2016-01-20 16:23 |
| This issue is becoming increasingly important as FreeBSD 11.0-RELEASE time nears. What remains to be done/identified/answers here to make progress? |
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| msg258691 - (view) |
Author: STINNER Victor (vstinner) * |
Date: 2016-01-20 16:27 |
| Andrew Turner: "Can this be applied?" koobs: "What remains to be done/identified/answers here to make progress?" *I* don't understand if replacing fpsetmask() with fedisableexcept() is enough, or if we also need to starting putting "#pragma STDC FENV_ACCESS ON" in all .c file using a C double? It's not a rhetorical question, I don't understand the consequence of the attached patch. If two FreeBSD developers (Andrew Turner and koobs) are confident, maybe I should trust them and apply blindly the patch without trying to understand it :-D |
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| msg258692 - (view) |
Author: Stefan Krah (skrah) * |
Date: 2016-01-20 16:30 |
| 1) Feedback whether the compiler used on FreeBSD recognizes FENV_ACCESS. 2) If not, an indication why the man page mentions it. |
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| msg258694 - (view) |
Author: Andrew Turner (Andrew Turner) |
Date: 2016-01-20 17:03 |
| I think this patch is correct. Clang, as shipped by FreeBSD, doesn't support FENV_ACCESS. It raises the following warning: fenv_test.c:2:14: warning: pragma STDC FENV_ACCESS ON is not supported, ignoring pragma [-Wunknown-pragmas] #pragma STDC FENV_ACCESS ON ^ 1 warning generated. I expect the man page mentions it because it is mentioned in the standard. In the bugs section it does say the pragma is unimplemented. |
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| msg258695 - (view) |
Author: Stefan Krah (skrah) * |
Date: 2016-01-20 17:10 |
| Thanks, then the patch looks good to me. |
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| msg258720 - (view) |
Author: Roundup Robot (python-dev) |
Date: 2016-01-20 21:31 |
| New changeset 76f35f35be50 by Victor Stinner in branch '3.5': Replace fpgetmask() with fedisableexcept() https://hg.python.org/cpython/rev/76f35f35be50 New changeset 6134d9ecab60 by Victor Stinner in branch 'default': Merge 3.5 (issue #24520) https://hg.python.org/cpython/rev/6134d9ecab60 New changeset 394ae9efc5c2 by Victor Stinner in branch '2.7': Replace fpgetmask() with fedisableexcept() https://hg.python.org/cpython/rev/394ae9efc5c2 |
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| msg258721 - (view) |
Author: STINNER Victor (vstinner) * |
Date: 2016-01-20 21:33 |
| "I expect the man page mentions it because it is mentioned in the standard. In the bugs section it does say the pragma is unimplemented." Ah ah, funnny. Sorry, I was confused by the manual page. I pushed your patch to Python 2.7, 3.5 and default (3.6) branches. @koobs: sorry, 3.4 now only accept security fixes :-p |
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| msg258819 - (view) |
Author: STINNER Victor (vstinner) * |
Date: 2016-01-22 16:04 |
| > @koobs: sorry, 3.4 now only accept security fixes :-p I wrote a table giving the status of each Python branch to know which ones still accept bugfixes or not: https://docs.python.org/devguide/#status-of-python-branches |
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