configure script cannot detect float word ordering on linux

[sourishbasu]

BPO	45477
Nosy	@tiran
Files	config.log conftest.o conftest.c conftest_unoptimized.o

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2021-10-14.21:19:53.235>
labels = ['build', 'expert-installation', '3.10']
title = 'configure script cannot detect float word ordering on linux'
updated_at = <Date 2021-10-22.22:49:31.555>
user = 'https://bugs.python.org/sourishbasu'

bugs.python.org fields:

activity = <Date 2021-10-22.22:49:31.555>
actor = 'sourish.basu'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Installation']
creation = <Date 2021-10-14.21:19:53.235>
creator = 'sourish.basu'
dependencies = []
files = ['50364', '50374', '50375', '50376']
hgrepos = []
issue_num = 45477
keywords = []
message_count = 12.0
messages = ['403951', '403978', '404096', '404135', '404138', '404447', '404448', '404449', '404450', '404459', '404463', '404836']
nosy_count = 2.0
nosy_names = ['christian.heimes', 'sourish.basu']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'compile error'
url = 'https://bugs.python.org/issue45477'
versions = ['Python 3.10']

Linked PRs

• gh-89640: properly detect float word ordering on Linux #125571
• gh-89640: Hardcode WASM float word ordering as little endian #126387
• [3.13] gh-89640: harden float word ordering (#125571 and #126387) #126429
• [3.12] gh-89640: harden float word ordering (#125571 and #126387) #126430
• gh-89640: Restore configure error message on failure to detect float word order #126569
• gh-89640: Pull in update to float word order detection in autoconf-archive #126747

[sourishbasu]

I am trying to compile Python 3.10.0 on a Red Hat linux system with intel C/C++ compilers. This is my configure command:

./configure --with-computed-gotos --without-gcc --with-ensurepip=install --enable-optimizations --with-libm=-limf --with-cxx-main=icpc --with-threads --enable-ipv6 --with-signal-module CC=icc CXX=icpc LD=xild AR=xiar LIBS='-lpthread -limf -lirc' CFLAGS='-O3 -fPIC -fp-model strict -fp-model source -axCORE-AVX512,CORE-AVX2 -xAVX -ipo -prec-div -prec-sqrt' LDFLAGS='-ipo' CPP='icc -E'

The failure comes as follows:

checking for --with-libm=STRING... set LIBM="-limf"
checking for --with-libc=STRING... default LIBC=""
checking for x64 gcc inline assembler... yes
checking whether float word ordering is bigendian... unknown
configure: error:

Unknown float word ordering. You need to manually preset
ax_cv_c_float_words_bigendian=no (or yes) according to your system.

I saw bpo-38527 was fixed in 3.10. Perhaps fixing it on Solaris broke it on some other platforms?

[tiran]

Python uses the AX_C_FLOAT_WORDS_BIGENDIAN macro from autoconf-archive to detect byte order of floats. You can find the code at https://www.gnu.org/software/autoconf-archive/ax_c_float_words_bigendian.html .

Please attach your config.log file and the conftest.o output file of the follow command:

$ cat > conftest.c << EOF
double d = 90904234967036810337470478905505011476211692735615632014797120844053488865816695273723469097858056257517020191247487429516932130503560650002327564517570778480236724525140520121371739201496540132640109977779420565776568942592.0;
EOF
$ icc -c conftest.c

[sourishbasu]

See attached my config log.

When I tried to compile conftest.c with 'icc -c conftest.c', it produced 'conftest.o' without any errors.

[tiran]

Please build conftest.o with compiler flags

icc -c -O3 -fPIC -fp-model strict -fp-model source -axCORE-AVX512,CORE-AVX2 -xAVX -ipo -prec-div -prec-sqrt 

and attach the file.

[sourishbasu]

I executed:

$ icc -c -O3 -fPIC -fp-model strict -fp-model source -axCORE-AVX512,CORE-AVX2 -xAVX -ipo -prec-div -prec-sqrt conftest.c

and conftest.o was built without errors. It has one symbol, as expected:

$ nm conftest.o
                 U __must_be_linked_with_icc_or_xild
0000000000000000 D d

[tiran]

Please upload and attach the .o file to this bug. I need to see the content of the file.

[sourishbasu]

conftest.o attached

[sourishbasu]

conftest.c attached

[tiran]

Your conftest.o does not contain the magic string "seesnoon". Either ICC uses a different serialization format or your CFLAGS optimize the value away.

Please run

icc -c -o conftest_unoptimized.o conftest.c

and upload "conftest_unoptimized.o".