Re: DO NOT use file format of /bin/sh for x32 detection!

[Thorsten Glaser]

On Thu, 1 Mar 2018, James Clarke wrote:

> x32, so it's not a *pure* system, but build=host=target=x32.

Well, “pure” x32 systems don’t exist, as it’s a userland-only
architecture, the kernel is simply amd64 for example. Same for
arm64ilp32 and arm64/aarch64 and perhaps(?) MIPS n32/n64.

Worse, x32 users are expected to run mixed (Multi-Arch)
systems, usually with amd64, though mine uses i386 for
those binaries not working with x32 yet.

But this is not even the case here: the x32 binary of any
utility built with klibc is indistinguishable from the
amd64 binary of the same utility built with klibc because
klibc treats x32 as amd64.


For --build= I agree checking the compiler isn’t usually
necessary, and the build system should be similar enough
to amd64, so checking a binary is a somewhat(!) sensible
approach. I’d suggest checking the uname binary, since
it’s unlikely to be built into the shell and called from
config.guess anyway, or perhaps $CC, although that could
have arguments so only its first word.

A slight issue could arise from programs that do use
HOST_CC/CC_FOR_BUILD to create code targetting the build
environment, e.g. for generation of source code. However,
these are unlikely to need foo64ilp32-specific treatment,
and assembly code users are requested to change their code
to check defined(__ILP32__) already anyway, so the result
of config.guess would rarely be used.

I’d still prefer checking CC_FOR_BUILD for correctness,
personally, though. But then, I’m a BSD person…


For --host= checking the compiler is an absolute must,
though. --target= must be manually passed, so that’s
indeed not needing consideration.

bye,
//mirabilos
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