Re: [musl] Re: OS detection wrong on Alpine Linux 3.10

[Ariadne Conill]

Hello,

On 2020-09-20 04:12, Dmitry V. Levin wrote:
> On Sat, Sep 19, 2020 at 03:30:54PM +0200, Bruno Haible wrote:
> > The value of $host_os, determined by the current config.guess, is:
> >    - On Alpine Linux 3.9: linux-musl
> >    - On Alpine Linux 3.10: linux-gnu
> >    - On Alpine Linux 3.12: linux-musl
> >
> > The reason is that config.guess tests 'ldd --version'. However, in
> > Alpine Linux 3.10, /usr/bin/ldd has been replaced with a shell script
> > that does not understand the --version option:
> >
> > $ cat /usr/bin/ldd
> > #!/bin/sh
> > exec /lib/ld-musl-x86_64.so.1 --list -- "$@"
> > $ /usr/bin/ldd --version 2>&1
> > /lib/ld-musl-x86_64.so.1: cannot load --version: No such file or directory
> >
> > Find attached a proposed fix. More details in
> > <https://lists.gnu.org/archive/html/bug-gnulib/2020-09/msg00098.html>.
> >
> > Bruno
>
> > >From 6e8da56c68ad94175d67acfc6257e614fe74e01d Mon Sep 17 00:00:00 2001
> > From: Bruno Haible <bruno@clisp.org>
> > Date: Sat, 19 Sep 2020 15:24:59 +0200
> > Subject: [PATCH] * config.guess: Fix determination of musl libc on Alpine
> >   Linux 3.10.
> >
> > ---
> >   ChangeLog    |  5 +++++
> >   config.guess | 14 ++++++--------
> >   2 files changed, 11 insertions(+), 8 deletions(-)
> >
> > diff --git a/ChangeLog b/ChangeLog
> > index 4f106db..834f4e5 100644
> > --- a/ChangeLog
> > +++ b/ChangeLog
> > @@ -1,3 +1,8 @@
> > +2020-09-19  Bruno Haible  <bruno@clisp.org>
> > +
> > +       * config.guess: Don't use 'ldd --version' to determine the presence of
> > +       musl libc, as this fails on Alpine Linux 3.10.
> > +
> >   2020-09-08  Elad Lahav  <e2lahav@gmail.com>
> >             Ben Elliston  <bje@gnu.org>
> >   
> > diff --git a/config.guess b/config.guess
> > index 9aff91c..8d70ec2 100755
> > --- a/config.guess
> > +++ b/config.guess
> > @@ -2,7 +2,7 @@
> >   # Attempt to guess a canonical system name.
> >   #   Copyright 1992-2020 Free Software Foundation, Inc.
> >   
> > -timestamp='2020-08-17'
> > +timestamp='2020-09-19'
> >   
> >   # This file is free software; you can redistribute it and/or modify it
> >   # under the terms of the GNU General Public License as published by
> > @@ -150,17 +150,15 @@ Linux|GNU|GNU/*)
> >         #elif defined(__dietlibc__)
> >         LIBC=dietlibc
> >         #else
> > +       #include <stdarg.h>
> > +       #ifdef __DEFINED_va_list
> > +       LIBC=musl
> > +       #else
> >         LIBC=gnu
> >         #endif
> > +       #endif
> >         EOF
> >         eval "`$CC_FOR_BUILD -E "$dummy.c" 2>/dev/null | grep '^LIBC' | sed 's, 
> > ,,g'`"
> > -
> > -       # If ldd exists, use it to detect musl libc.
> > -       if command -v ldd >/dev/null && \
> > -               ldd --version 2>&1 | grep -q ^musl
> > -       then
> > -           LIBC=musl
> > -       fi
> >         ;;
> >   esac
> >   
>
> Is this __DEFINED_va_list macro the official way of detecting musl?
> It looks very fragile to me.

There is no official way of detecting musl.

Ariadne