@affeldt-aist @t6s
I’m not sure what caused this error. Is there anything I should do on my side?

Here is the error message:

File "./reals/signed.v", line 6, characters 29-37:
Error: Cannot find a physical path bound to logical path
unstable with prefix mathcomp.

and here is the problematic code:

From HB Require Import structures.
From mathcomp Require Import ssreflect ssrfun ssrbool.
From mathcomp Require Import ssrnat eqtype choice order ssralg ssrnum ssrint.
#[warning="-warn-library-file-internal-analysis"]
From mathcomp Require Import unstable.
From mathcomp Require Import mathcomp_extra.

I don't understand why it fails suddenly (maybe @proux01 knows)
but do not worry: signed.v is a deprecated file, I will test on my side ASAP,
worst case scenario: we don't find a fix, then we might simply give up on Coq 8.20.

@affeldt-aist
Thank you for investigating this error. I really appreciate your help.

Mmmhhh... I can't reproduce the error locally. :-(

(Sorry, I made a push force but at least it is updated w.r.t. master.)
I tried to simplify your proof using a theory for the positive/negative part of real functions taken from PR #1391 (not merged yet).
I think it is better to do the proof this way because it contributes to a theory that is useful elsewhere.
What do you think?
(I still need one pass to complete the review.)

@affeldt-aist
Thank you for your suggestion. I agree with you. The positive/negative part of real-valued functions is an important notion and appears everywhere in the Lebesgue integral theory.