Re: [sr #110846] cross-compilation is not entered when build_alias and host_alias are the same

[Lang Daniel]

> On 2023-03-01, anonymous <INVALID.NOREPLY@gnu.org> wrote:
>> This might be the desired use case, but when cross compiling with
>> systems like buildroot one might have the same architecture on
>> --build and --host.
>>
>> Example: Compile on Apple silicon (aarch64-unknown-linux-gnu) for a Cortex
>> A75 based system (aarch64-unknown-linux-gnu). Cross compiling isn't
>> automatically detected.
>
> By setting --host and --build to the same value, this explicitly forces
> non-cross-compilation mode in configure.
> 
> If you specify --host without also specifying --build, then configure will
> run the auto-detection which I expect will work properly for you.

Looking into configure setting --host without --build will trigger a test
where an executable is run to determine whether or not cross compiling is
happening. Which in this case may or may not fail.

The manual states:
"Therefore, whenever you specify --host, be sure to specify --build too."

> 
> Probably the "vendor" field of the host triplet should have been set to
> something different for these different systems, but I digress...

Buildroot adds itself as the vendor (aarch64-buildroot-linux-gnu) but
libgpg-error uses the host triplet to lookup a matching syscfg. Therefore
the it has to be changed to aarch64-unknown-linux-gnu.

> 
>> And there seems to be no way to force it if we know that we are cross
>> compiling.
>
> Nevertheless, you can always force cross compilation mode by explicitly
> setting cross_compiling=yes, for example:
> 
>   % ./configure cross_compiling=yes

Thanks for the tip. I tried --cross_compiling=yes which wasn't registered
leading me to believe that there is no way to force it.

> 
> Hope that helps,
>   Nick

Regards
Daniel