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

[Ariadne Conill <ariadne@dereferenced.org>]

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