Rename --target to --host for autotools conventions

[metajack]

There are three cross compiling parameters that autotools generally uses: BUILD, TARGET, and HOST. BUILD is the machine the compiler is running on. HOST is the machine the resulting code will run on. TARGET is only useful when building a compiler to denote what target the compiler (running on HOST) will generate code for.

If you want to cross compile a standard autotools package, you pass --host not --target (note: that this is not the case for spidermonkey specifically, but it is documented there that they use a weird convention).

rustc's use of --target here breaks with these conventions. I noticed this recently when trying to debug native library builds in Servo because I was passing --target to configure incorrectly.

[brson]

That's slightly embarrassing if we've gotten these terms backwards for years! We should compare to LLVM because that's surely where we took inspiration.

[brson]

Hm, are you suggesting we rename the argument to configure and rustc or just one?

The --host argument to configure should do as you say - produce a compiler that runs on that architecture.

[brson]

clang seems to use --target for this.

[metajack]

I'm only talking about the --target argument to rustc. The configure args are appropriate since the build is generating a compiler.

[brson]

Nominating since this flag would be awkward to change later.

[emberian]

Given that GCC (and autotools in general) doesn't even have the concept of multi-"host" cross compilation, I think we ought to follow LLVM and Clang's lead here. (Plus I think it reads better: rustc --target foo, "this executable is targeting the foo platform".) No strong feelings though.

[metajack]

@cmr I'm not exactly sure what you mean. GCC on Fedora can produce 64bit or 32bit binaries, and to select this behavior in an autotools project you pass in --host.

Clang also does not support --target or --host or --build. Instead it has -march=CPU. Perhaps the Clang build system has these flags, but it is building a compiler, so it makes sense for it to have --target.

LLVM's configure has --target because it is building a compiler library, which is the same reason Rust's configure has and needs --target.

[emberian]

clang --target=foo does the same thing as rustc --target=foo.

On Sat, Aug 16, 2014 at 10:21 AM, Jack Moffitt notifications@github.com
wrote:

@cmr https://github.com/cmr I'm not exactly sure what you mean. GCC on
Fedora can produce 64bit or 32bit binaries, and to select this behavior in
an autotools project you pass in --host.

Clang also does not support --target or --host or --build. Instead it has
-march=CPU. Perhaps the Clang build system has these flags, but it is
building a compiler, so it makes sense for it to have --target.

LLVM's configure has --target because it is building a compiler library,
which is the same reason Rust's configure has and needs --target.

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[metajack]

@cmr Ok. That makes more sense. That argument wasn't described in the man page I looked at.

[pnkfelix]

Based on the dialogue here, it sounds like @metajack is trying to argue for a change to the rustc arguments based on the conventions for configure switches in a canandian cross setup.

But they are two different things... and it seems like it would make the most sense for us to choose options that are consistent with what clang does.

Closing for now. @metajack, feel free to correct any misunderstanding in my synopsis.