parallel/test-buffer-writefloat wrong assumption of NaN representation on mipsel ?

[kapouer]

Version

16.14.2

Platform

debian/bookworm

Subsystem

test

What steps will reproduce the bug?

on mipsel, Quad Core Loongson 3A3000,
Test fails at

node/test/parallel/test-buffer-writefloat.js

Lines 61 to 63 in 3bd87e1

	assert.ok(
	buffer.equals(new Uint8Array(
	[ 0x7F, 0xC0, 0x00, 0x00, 0x00, 0x00, 0xC0, 0x7F ])));

How often does it reproduce? Is there a required condition?

It doesn't fail on all mips CPU debian is using to build their packages.

What is the expected behavior?

The test should succeed in comparing internal representations of NaN, regardless of the CPU ?

What do you see instead?

not ok 184 parallel/test-buffer-writefloat
  ---
  duration_ms: 0.408
  severity: fail
  exitcode: 1
  stack: |-
    node:assert:399
        throw err;
        ^
    
    AssertionError [ERR_ASSERTION]: The expression evaluated to a falsy value:
    
      assert.ok(
        buffer.equals(new Uint8Array(
          [ 0x7F, 0xC0, 0x00, 0x00, 0x00, 0x00, 0xC0, 0x7F ])))
    
        at Object.<anonymous> (/<<PKGBUILDDIR>>/test/parallel/test-buffer-writefloat.js:61:10)
        at Module._compile (node:internal/modules/cjs/loader:1103:14)
        at Object.Module._extensions..js (node:internal/modules/cjs/loader:1157:10)
        at Module.load (node:internal/modules/cjs/loader:981:32)
        at Function.Module._load (node:internal/modules/cjs/loader:822:12)
        at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:77:12)
        at node:internal/main/run_main_module:17:47 {
      generatedMessage: true,
      code: 'ERR_ASSERTION',
      actual: false,
      expected: true,
      operator: '=='
    }

Additional information

This is for reference.
I know mipsel is not officially supported, but some people might find this report useful.

[bnoordhuis]

What does the buffer contain? mipsel has IEEE-style floats, right? Any double with with an all-bits-one exponent (0x7FF) and a non-zero fraction is a NaN.

[kapouer]

For now all I know is that the test pass on mipsel-osuosl-04 but not mipsel-osuosl-05 (see below for details about archs),
and that mipsel-osuosl-05 has the old IEEE 754-2008 standard.

mipsel-osuosl-04

system type : Generic Loongson64 System
machine : loongson,loongson64c-4core-rs780e
processor : 0
cpu model : ICT Loongson-3 V0.9 FPU V0.1
BogoMIPS : 2992.12
wait instruction : yes
microsecond timers : yes
tlb_entries : 1088
extra interrupt vector : no
hardware watchpoint : no
isa : mips1 mips2 mips3 mips4 mips5 mips32r1 mips32r2 mips64r1 mips64r2
ASEs implemented : dsp dsp2 vz loongson-mmi loongson-cam loongson-ext loongson-ext2
shadow register sets : 1
kscratch registers : 6
package : 0
core : 0
VCED exceptions : not available
VCEI exceptions : not available

mipsel-osuosl-05

system type : Generic Loongson64 System
machine : loongson,loongson64g-4core-ls7a
processor : 0
cpu model : ICT Loongson-3 V0.4 FPU V0.1
BogoMIPS : 3592.19
wait instruction : yes
microsecond timers : yes
tlb_entries : 2112
extra interrupt vector : no
hardware watchpoint : no
isa : mips1 mips2 mips3 mips4 mips5 mips32r1 mips32r2 mips64r1 mips64r2
ASEs implemented : vz msa loongson-mmi loongson-cam loongson-ext loongson-ext2
shadow register sets : 1
kscratch registers : 6
package : 0
core : 0
VCED exceptions : not available
VCEI exceptions : not available

[kapouer]

Closing, debian dropped mipsel in favor of mips64el.