Re: [PATCH] Correctly determine libc.so 'OUTPUT_FORMAT' when cross-compiling.

[Fangrui Song <maskray@google.com>]

On 2022-10-07, Ludovic Courtès via Libc-alpha wrote:
>Hi Carlos,
>
>Carlos O'Donell <carlos@redhat.com> skribis:
>
>> On Thu, Jul 01, 2021 at 11:00:19PM +0200, Ludovic Courtès via Libc-alpha wrote:
>>> Commit 87d583c6e8cd0e49f64da76636ebeec033298b4d replaces the sed script
>>> with an "objdump -f" invocation to determine the 'OUTPUT_FORMAT' bit of
>>> the libc.so linker script.
>>>
>>> However, when cross-compiling, for example from x86_64-linux-gnu to
>>> aarch64-linux-gnu, "objdump -f" would report the wrong
>>> format ("elf64-little").  Conversely, "aarch64-linux-gnu-objdump -f"
>>> reports "elf64-littleaarch64" as expected.
>>>
>>> This patch changes 'configure.ac' to use AC_CHECK_TOOL rather than
>>> '$CC -print-prog-name=objdump' to determine the value of the OBJDUMP
>>> variable.  That way, OBJDUMP is set to TRIPLET-objdump when
>>> cross-compiling for TRIPLET.
>>
>> I've been tackling a backlog of old glibc patches, and this one is up
>> next. Yes it's been over a year, but this patch still applies and the
>> idea is sound. I've tested this with build-many-glibcs (bmg) on x86_64
>> and it has no impact because bmg always sets OBJDUMP. My opinion is that
>> bmg is the "base standard" for how we build native and cross tooling and
>> so it your changes work here, they should work in other instances.
>>
>> The change looks good to me.
>>
>> No regresions on x86_64.
>>
>> Would you like me to commit this? :-)
>
>I don’t have commit access AFAIK so I’ll happily defer to you.  :-)
>
>Thanks for taking the time to look at the backlog!
>
>Ludo’.

Thanks. This looks good.