add zig build support for -static

[elerch]

This allows forcing exe output to be statically linked, similar to the pre-existing is_dynamic flag. Setting the flag will pass -static to the zig build-exe command. Usage example:

// const std = @import("std");
const Builder = @import("std").build.Builder;

pub fn build(b: *Builder) void {
    // Standard target options allows the person running `zig build` to choose
    // what target to build for. Here we do not override the defaults, which
    // means any target is allowed, and the default is native. Other options
    // for restricting supported target set are available.
    const target = b.standardTargetOptions(.{});

    // Standard release options allow the person running `zig build` to select
    // between Debug, ReleaseSafe, ReleaseFast, and ReleaseSmall.
    const mode = b.standardReleaseOptions();
    const exe = b.addExecutable("hello", "src/main.zig");

    exe.is_static = true;
    exe.install();

    const run_cmd = exe.run();
    run_cmd.step.dependOn(b.getInstallStep());
    if (b.args) |args| {
        run_cmd.addArgs(args);
    }

    const run_step = b.step("run", "Run the app");
    run_step.dependOn(&run_cmd.step);
}

[data-man]

...
exe.is_static = true;
exe.is_dynamic = true;
...

What will happen here?

[elerch]

Good question. I tried setting -static and -dynamic on zig build-exe so I could match the behavior. However, zig build-exe doesn't have a lot of smarts in this regard.

zig build-exe -static -dynamic: results in a dynamic executable
zig build-exe -dynamic -static: results in a static executable

Since the code sets -static last, we should see a static executable produced.

I'm open to whatever behavior we think is correct here, but I thought to open the conversation, getting the flag at least accessible would be preferred. I had considered making is_dynamic optional, so setting to false would indicate static, null would be normal behavior, or true would be dynamic linking, but is_dynamic is used in a few other places and given the zig build-exe behavior I felt this was more consistent with the CLI.

[tauoverpi]

If both are true it should just throw an error and request the user removes one of them.

I had considered making is_dynamic optional

In this case it would be better to just have an enum ?enum { static, dynamic } as it expresses the intent better.

[elerch]

If both are true it should just throw an error and request the user removes one of them.

I think this is the crux of the question. zig build-exe does not currently throw an error if both -dynamic and -static are specified. If an error were to be thrown, it should probably do so on zig build-exe. I assume errors are bubbled up, so maybe that should be in separate PR/issue?

Alternatively, there could be a check in build.zig, but then there's (admittedly minimal) duplicated logic...

[elerch]

I created #8258 to disallow -dynamic and -static at the CLI when calling zig build-exe. This appears to bubble up appropriately through the build mechanism as well, so I'm not sure we need a second check in std/lib/build.zig for this case.

[Vexu]

As noted by others, this flag works more like an enum than bools so build.zig should be changed to have linkage: ?enum { static, dynamic } = null instead. Let me know if you are interested in implementing this chage.

Also sorry for taking so long with reviewing this, I'm trying to put more effort into keeping the review queue more manageable.

[elerch]

ok - new changes @Vexu. I rebased to 0.8.0 and removed is_dynamic/is_static in favor of link_mode, which seemed more consistent. I was also able to leverage the existing std.builtin.LinkMode. The change is more involved and is now a breaking
change as it touches a public function and removes the existing is_dynamic bool. Looks like there's also a minor conflict with master (as this is based on 0.8.0 tag). Please take a look.

[Vexu]

It turns that #7959 already mostly implemented having linkage as an enum making this pr unnecessary.
Once again sorry about losing your pr in the review queue, we'll try to keep the amount of open prs more manageable in the future. Hopefully this doesn't discourage you from contributing in the future.

[elerch]

I see the changes in #7959 - I agree they look like they'll solve this issue too. Definitely not discouraged - happy to help, even if it turns out only to further the discussion along.