From: Mark H Weaver <mhw@netris.org>
To: "Ludovic Courtès" <ludo@gnu.org>
Cc: guix-devel@gnu.org
Subject: Re: Pass --build=<triplet> to native builds by default?
Date: Sat, 03 Jan 2015 17:15:42 -0500 [thread overview]
Message-ID: <871tnby0hd.fsf@netris.org> (raw)
In-Reply-To: <8761cny0o2.fsf@netris.org> (Mark H. Weaver's message of "Sat, 03 Jan 2015 17:11:41 -0500")
Mark H Weaver <mhw@netris.org> writes:
> ludo@gnu.org (Ludovic Courtès) writes:
>
>> Mark H Weaver <mhw@netris.org> skribis:
>>
>>> It turns out that on ARM systems, the result of 'config.guess' depends
>>> on the result of 'uname -m'. In other words, details of the kernel (and
>>> perhaps processor?) on the build machine will determine the triplet of
>>> our builds, which in turn may affect what set of instructions is used.
>>
>> Do you know how the ‘uname -m’ output is used in config.guess? What
>> does it return on ARM?
>
> The output of 'uname -m' becomes the first (cpu) component of the GNU
> triplet. uname(1) gets its information from the kernel via the uname(2)
> system call. The field returned by 'uname -m' is described as "Hardware
> identifier". See <http://man7.org/linux/man-pages/man2/uname.2.html>.
>
> Here's the relevant section of config.guess from gcc-4.8.4:
>
> arm*:Linux:*:*)
> eval $set_cc_for_build
> if echo __ARM_EABI__ | $CC_FOR_BUILD -E - 2>/dev/null \
> | grep -q __ARM_EABI__
> then
> echo ${UNAME_MACHINE}-unknown-linux-${LIBC}
> else
> if echo __ARM_PCS_VFP | $CC_FOR_BUILD -E - 2>/dev/null \
> | grep -q __ARM_PCS_VFP
> then
> echo ${UNAME_MACHINE}-unknown-linux-${LIBC}eabi
> else
> echo ${UNAME_MACHINE}-unknown-linux-${LIBC}eabihf
> fi
> fi
> exit ;;
I forgot to answer your second question. On my Novena, 'uname -m'
returns "armv7l". The problem is this: I suspect that if the build
machine has an armv8 processor, it will return something different like
"armv8l".
Mark
next prev parent reply other threads:[~2015-01-03 22:15 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-01-03 20:01 Pass --build=<triplet> to native builds by default? Mark H Weaver
2015-01-03 21:01 ` Ludovic Courtès
2015-01-03 22:11 ` Mark H Weaver
2015-01-03 22:15 ` Mark H Weaver [this message]
2015-01-04 16:20 ` Ludovic Courtès
2015-01-04 19:11 ` Mark H Weaver
2015-01-04 20:18 ` Ludovic Courtès
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