erfa build on Debian/arm (32 bit) fails

[olebole]

During a recent rebuild of the erfa Debian package, we observed failures during the test:

FAIL: t_erfa_c
==============

eraApco failed: eb(1) want -0.97418271106303222506 got -0.97420736878151714677 (1/3.95e+04)
eraApco failed: eb(2) want -0.21151301901353447565 got -0.21149874102317881008 (1/1.48e+04)
eraApco failed: eb(3) want -0.091798401869495324656 got -0.091758253265154784972 (1/2.29e+03)
eraApco failed: eh(1) want -0.97364255716897385451 got -0.97365029660194080119 (1/1.26e+05)
eraApco failed: eh(2) want -0.20924521258493308795 got -0.20922729557210567597 (1/1.17e+04)
eraApco failed: eh(3) want -0.090755781522432729669 got -0.090714049157423246039 (1/2.17e+03)
eraApco failed: em want 0.99982332417099573085 got 0.9998407017170692912 (1/5.75e+04)
eraApco failed: v(1) want 2.0787049929167285988e-05 got 2.0267460037523643508e-05 (1/40)
eraApco failed: v(2) want -8.9553601071519516909e-05 got -9.045276251218313556e-05 (1/99.6)
eraApco failed: v(3) want -3.8633389942889509385e-05 got -3.8632734450558535748e-05 (1/5.89e+04)
eraApco failed: bm1 want 0.99999999502775616111 got 0.99999999495751978884 (1/1.42e+10)
eraApco failed: sphi want -0.94401156790032114685 got 0 (1/1)
eraApco failed: cphi want 0.32991235149714748243 got 1 (1/0.492)
eraApco13 failed: eb(1) want -0.97418271073208750899 got -0.97420736845069633159 (1/3.95e+04)
eraApco13 failed: eb(2) want -0.21151301904897165662 got -0.2114987410587583494 (1/1.48e+04)
eraApco13 failed: eb(3) want -0.091798401894967560088 got -0.091758253329867603409 (1/2.29e+03)
eraApco13 failed: eh(1) want -0.97364255725869353064 got -0.97365029668816305275 (1/1.26e+05)
eraApco13 failed: eh(2) want -0.20924521216033362125 got -0.20922729514687662955 (1/1.17e+04)
eraApco13 failed: eh(3) want -0.09075578153885664745 got -0.090714049212753139484 (1/2.17e+03)
eraApco13 failed: em want 0.99982332409138985341 got 0.99984070164118143964 (1/5.75e+04)
eraApco13 failed: v(1) want 2.0787049945204892615e-05 got 2.0267460058253504343e-05 (1/40)
eraApco13 failed: v(2) want -8.9553601332388683347e-05 got -9.0452762775764216892e-05 (1/99.6)
eraApco13 failed: v(3) want -3.8633389930558871301e-05 got -3.863273443823356262e-05 (1/5.89e+04)
eraApco13 failed: bm1 want 0.99999999502775605009 got 0.99999999495751978884 (1/1.42e+10)
eraApco13 failed: xpl want 1.1334274181307530445e-06 got 2.1358677457347171193e-07 (1/1.23)
eraApco13 failed: ypl want 1.4533475957806461958e-06 got -1.2451396325257810176e-07 (1/0.921)
eraApco13 failed: sphi want -0.94401156790032114685 got 0 (1/1)
eraApco13 failed: cphi want 0.32991235149714748243 got 1 (1/0.492)
eraApio failed: refa want 0.00020141877900000000612 got 0 (1/1)
eraApio13 failed: xpl want 1.1334274181307530445e-06 got 2.1358677457347171193e-07 (1/1.23)
eraApio13 failed: ypl want 1.4533475957806461958e-06 got -1.2451396325257810176e-07 (1/0.921)
eraApio13 failed: diurab want 5.1358436616999133913e-07 got 5.13583023444664535e-07 (1/3.82e+05)
eraApio13 failed: refa want 0.00020141877859403969301 got 0 (1/1)
eraAtcc13 failed: ra want 2.7101265045313724933 got 2.7101264904151984858 (1/1.92e+08)
eraAtcc13 failed: da want 0.17406325376283501849 got 0.17406324946783852115 (1/4.05e+07)
eraAtci13 failed: ri want 2.7101215729686969347 got 2.7101247730618904797 (1/8.47e+05)
eraAtci13 failed: di want 0.17293713672195390463 got 0.17294162401707507959 (1/3.85e+04)
eraAtci13 failed: eo want -0.0029006187126573755933 got -0.0029002224353784880791 (1/7.32e+03)
eraAtco13 failed: aob want 0.092517744854855157866 got 6.1995162903251879172 (1/0.0151)
eraAtco13 failed: zob want 1.4076614052564992985 got 1.4074064431870036973 (1/5.52e+03)
eraAtco13 failed: hob want -0.092651544315297248988 got 0.083786462944530598618 (1/0.525)
eraAtco13 failed: dob want 0.17166265600725261198 got 0.17166500797861430905 (1/7.3e+04)
eraAtco13 failed: rob want 2.7102604535049610313 got 2.7103316590172661371 (1/3.81e+04)
eraAtco13 failed: eo want -0.0030205483548024127799 got -0.0030196951125513564473 (1/3.54e+03)
eraAtio13 failed: aob want 0.092339522248951227956 got 0.092339786537602636107 (1/3.49e+05)
eraAtio13 failed: zob want 1.4077587045135500077 got 1.4077594779431943373 (1/1.82e+06)
eraAtio13 failed: hob want -0.092476198798816980351 got -0.092476487587726960427 (1/3.2e+05)
eraAtio13 failed: dob want 0.17176534357562348032 got 0.17176610858481869415 (1/2.25e+05)
eraAtio13 failed: rob want 2.7100851079884806794 got 2.710085396776767741 (1/9.38e+06)
eraAtoc13 failed: R/rc want 2.709956744659136163 got 2.7099567448812713621 (1/1.22e+10)
eraAtoc13 failed: R/dc want 0.17416965008984713892 got 0.17416965008647250501 (1/5.16e+10)
eraAtoi13 failed: R/ri want 2.7101215744475406488 got 2.7101215746696327713 (1/1.22e+10)
eraAtoi13 failed: R/di want 0.17293718391166088 got 0.17293718390816764652 (1/4.95e+10)
eraC2tpe failed: 21 want -0.98341476414768047576 got -0.98341476217458345666 (1/4.98e+08)
eraC2tpe failed: 22 want -0.16598836354349952305 got -0.16598762356078863855 (1/2.24e+05)
eraC2tpe failed: 23 want 0.073097638980428203404 got 0.07309934583666775898 (1/4.28e+04)
eraC2tpe failed: 31 want 0.0010596854306732152867 got 0.0010615149354214984539 (1/579)
eraC2tpe failed: 32 want 0.39776318556050788144 got 0.39776349435780650188 (1/1.29e+06)
eraC2tpe failed: 33 want 0.91748750687927349556 got 0.91748737088981713317 (1/6.75e+06)
eraC2txy failed: 21 want -0.98347681341361425922 got -0.9834768123378392346 (1/9.14e+08)
eraC2txy failed: 22 want -0.18103322036495292369 got -0.18103322029093199541 (1/2.45e+09)
eraC2txy failed: 23 want 0.00057498008435941398622 got 0.00057684044329390138286 (1/309)
eraC2txy failed: 31 want 0.00057734740286192640871 got 0.0005791770230449705013 (1/316)
eraC2txy failed: 32 want 3.9618165469116245524e-05 got 3.995495229456762161e-05 (1/118)
eraC2txy failed: 33 want 0.99999983255017466099 got 0.99999983147877469225 (1/9.33e+08)
eraPmsafe failed: ra2 want 1.234087484501017018 got 1.2354071898593252943 (1/935)
eraPmsafe failed: dec2 want 0.78882499824504681563 got 0.78617713018408452719 (1/298)
eraPmsafe failed: pmr2 want 9.9964576635860741396e-06 got 9.9430790889184684123e-06 (1/187)
eraPmsafe failed: pmd2 want -2.0000400851067547266e-05 got -2.0006259343724926158e-05 (1/3.41e+03)
eraPmsafe failed: px2 want 0.0099999972953568310591 got 0.0099999143842941125293 (1/1.21e+05)
eraPmsafe failed: rv2 want 10.384683802939200348 got 16.203986952562850377 (1/1.78)
eraStarpm failed: ra want 0.016689190694142562454 got 0.014239415878370565577 (1/6.81)
eraStarpm failed: dec want -1.0939664542171279038 got -1.0936439038820793268 (1/3.39e+03)
eraStarpm failed: pmr want -1.783662682153176583e-05 got -1.7895280690075285606e-05 (1/304)
eraStarpm failed: pmd want 2.3380929159839896319e-06 got 2.3666031376788632112e-06 (1/82)
eraStarpm failed: px want 0.74735338353177194204 got 0.7490485523092883513 (1/441)
eraStarpm failed: rv want -21.599051704764171689 got -21.586002978204241742 (1/1.66e+03)
t_erfa_c validation failed!
FAIL t_erfa_c (exit status: 1)

============================================================================
Testsuite summary for erfa 2.0.0
============================================================================
# TOTAL: 2
# PASS:  1
# SKIP:  0
# XFAIL: 0
# FAIL:  1
# XPASS: 0
# ERROR: 0

The compiler is gcc 15.2.0; no build warnings appeared. All other architectures pass the test, including other 32-bit platforms and arm 64 bit. Many failures are by minimal floatbing point differences; however some (eraApco13/sphi or eraPmsafe/rv2) fail completely.

Full build log here

This was reported as Debian#1133139

[mhvk]

Yikes. And tricky as it involves routines which call lots of others.

There have been very few changes in erfa, so I suspect you'd get the same failures with an older version of erfa (or indeed with SOFA). Is this the case? Do less recent gcc work?

[sanvila]

There have been very few changes in erfa

Indeed. The failure happens with gcc-15 and glibc 2.42, but the same version (2.0.1) used to work ok with gcc-14 and glibc 2.40 in the past. This is the complete build history for armhf:

https://buildd.debian.org/status/logs.php?pkg=erfa&arch=armhf

[mhvk]

There have been very few changes in erfa

Indeed. The failure happens with gcc-15 and glibc 2.42, but the same version (2.0.1) used to work ok with gcc-14 and glibc 2.40 in the past. This is the complete build history for armhf:

https://buildd.debian.org/status/logs.php?pkg=erfa&arch=armhf

Yikes, so it is related to some compiler improvement or bug. I'm not quite sure what to do; as is, the ERFA code is essentially a straight copy of SOFA, so it seems likely the problem is in SOFA too, i.e., upstream. I'd tend to wait till the next point release and see if things improve on their own, and if not report upstream (whether SOFA or gcc). But will admit this is partially because I don't have the time to investigate...

[olebole]

The situation is a bit strange; I cannt reproduce the bug on our (Debians) "armhf" porterbox. I then tried to switch off optimization (-O0) and reverted to gcc-14, without luck: the problem persists on Debians "build daemons".

[mhvk]

How weird, so just to summarize, on the armhf porterbox erfa is build without problems, independent of gcc and optimization, but on the actual build machines, it now fails consistently, again independent of gcc and options. @sanvila mentioned that there also was a glibc update, from 2.4.0 to 2.4.2. Could that be the culprit?

[aurel32]

I have tracked down that to a dynamic linker issue when built against GCC 15. I have sent a patch:
https://inbox.sourceware.org/libc-alpha/20260510220041.169362-1-aurelien@aurel32.net

I therefore believe this issue can be closed.

[mhvk]

Wow, that is impressive sleuthing! I'll follow your suggestion to close this issue since this is now clearly a compiler bug.