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Auto merge of #114114 - keith:ks/always-add-lc_build_version-for-meta…
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…data-object-files, r=wesleywiser

Always add LC_BUILD_VERSION for metadata object files

As of Xcode 15 Apple's linker has become a bit more strict about the warnings it produces. One of those new warnings requires all valid Mach-O object files in an archive to have a LC_BUILD_VERSION load command:

```
ld: warning: no platform load command found in 'ARCHIVE[arm64][2106](lib.rmeta)', assuming: iOS-simulator
```

This was already being done for Mac Catalyst so this change expands this logic to include it for all Apple platforms. I filed this behavior change as FB12546320 and was told it was the new intentional behavior.
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bors committed Aug 29, 2023
2 parents 83995f3 + 2939e85 commit 84a9f4c
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Showing 4 changed files with 57 additions and 25 deletions.
29 changes: 12 additions & 17 deletions compiler/rustc_codegen_ssa/src/back/metadata.rs
Original file line number Diff line number Diff line change
Expand Up @@ -226,9 +226,7 @@ pub(crate) fn create_object_file(sess: &Session) -> Option<write::Object<'static

let mut file = write::Object::new(binary_format, architecture, endianness);
if sess.target.is_like_osx {
if let Some(build_version) = macho_object_build_version_for_target(&sess.target) {
file.set_macho_build_version(build_version)
}
file.set_macho_build_version(macho_object_build_version_for_target(&sess.target))
}
let e_flags = match architecture {
Architecture::Mips => {
Expand Down Expand Up @@ -334,31 +332,28 @@ pub(crate) fn create_object_file(sess: &Session) -> Option<write::Object<'static
Some(file)
}

/// Apple's LD, when linking for Mac Catalyst, requires object files to
/// contain information about what they were built for (LC_BUILD_VERSION):
/// the platform (macOS/watchOS etc), minimum OS version, and SDK version.
/// This returns a `MachOBuildVersion` if necessary for the target.
fn macho_object_build_version_for_target(
target: &Target,
) -> Option<object::write::MachOBuildVersion> {
if !target.llvm_target.ends_with("-macabi") {
return None;
}
/// Since Xcode 15 Apple's LD requires object files to contain information about what they were
/// built for (LC_BUILD_VERSION): the platform (macOS/watchOS etc), minimum OS version, and SDK
/// version. This returns a `MachOBuildVersion` for the target.
fn macho_object_build_version_for_target(target: &Target) -> object::write::MachOBuildVersion {
/// The `object` crate demands "X.Y.Z encoded in nibbles as xxxx.yy.zz"
/// e.g. minOS 14.0 = 0x000E0000, or SDK 16.2 = 0x00100200
fn pack_version((major, minor): (u32, u32)) -> u32 {
(major << 16) | (minor << 8)
}

let platform = object::macho::PLATFORM_MACCATALYST;
let min_os = (14, 0);
let sdk = (16, 2);
let platform =
rustc_target::spec::current_apple_platform(target).expect("unknown Apple target OS");
let min_os = rustc_target::spec::current_apple_deployment_target(target)
.expect("unknown Apple target OS");
let sdk =
rustc_target::spec::current_apple_sdk_version(platform).expect("unknown Apple target OS");

let mut build_version = object::write::MachOBuildVersion::default();
build_version.platform = platform;
build_version.minos = pack_version(min_os);
build_version.sdk = pack_version(sdk);
Some(build_version)
build_version
}

pub enum MetadataPosition {
Expand Down
8 changes: 3 additions & 5 deletions compiler/rustc_driver_impl/src/lib.rs
Original file line number Diff line number Diff line change
Expand Up @@ -852,11 +852,9 @@ fn print_crate_info(
use rustc_target::spec::current_apple_deployment_target;

if sess.target.is_like_osx {
println_info!(
"deployment_target={}",
current_apple_deployment_target(&sess.target)
.expect("unknown Apple target OS")
)
let (major, minor) = current_apple_deployment_target(&sess.target)
.expect("unknown Apple target OS");
println_info!("deployment_target={}", format!("{major}.{minor}"))
} else {
handler
.early_error("only Apple targets currently support deployment version info")
Expand Down
43 changes: 40 additions & 3 deletions compiler/rustc_target/src/spec/apple_base.rs
Original file line number Diff line number Diff line change
Expand Up @@ -179,20 +179,52 @@ pub fn opts(os: &'static str, arch: Arch) -> TargetOptions {
}
}

pub fn deployment_target(target: &Target) -> Option<String> {
pub fn sdk_version(platform: u32) -> Option<(u32, u32)> {
// NOTE: These values are from an arbitrary point in time but shouldn't make it into the final
// binary since the final link command will have the current SDK version passed to it.
match platform {
object::macho::PLATFORM_MACOS => Some((13, 1)),
object::macho::PLATFORM_IOS
| object::macho::PLATFORM_IOSSIMULATOR
| object::macho::PLATFORM_TVOS
| object::macho::PLATFORM_TVOSSIMULATOR
| object::macho::PLATFORM_MACCATALYST => Some((16, 2)),
object::macho::PLATFORM_WATCHOS | object::macho::PLATFORM_WATCHOSSIMULATOR => Some((9, 1)),
_ => None,
}
}

pub fn platform(target: &Target) -> Option<u32> {
Some(match (&*target.os, &*target.abi) {
("macos", _) => object::macho::PLATFORM_MACOS,
("ios", "macabi") => object::macho::PLATFORM_MACCATALYST,
("ios", "sim") => object::macho::PLATFORM_IOSSIMULATOR,
("ios", _) => object::macho::PLATFORM_IOS,
("watchos", "sim") => object::macho::PLATFORM_WATCHOSSIMULATOR,
("watchos", _) => object::macho::PLATFORM_WATCHOS,
("tvos", "sim") => object::macho::PLATFORM_TVOSSIMULATOR,
("tvos", _) => object::macho::PLATFORM_TVOS,
_ => return None,
})
}

pub fn deployment_target(target: &Target) -> Option<(u32, u32)> {
let (major, minor) = match &*target.os {
"macos" => {
// This does not need to be specific. It just needs to handle x86 vs M1.
let arch = if target.arch == "x86" || target.arch == "x86_64" { X86_64 } else { Arm64 };
macos_deployment_target(arch)
}
"ios" => ios_deployment_target(),
"ios" => match &*target.abi {
"macabi" => mac_catalyst_deployment_target(),
_ => ios_deployment_target(),
},
"watchos" => watchos_deployment_target(),
"tvos" => tvos_deployment_target(),
_ => return None,
};

Some(format!("{major}.{minor}"))
Some((major, minor))
}

fn from_set_deployment_target(var_name: &str) -> Option<(u32, u32)> {
Expand Down Expand Up @@ -274,6 +306,11 @@ fn ios_deployment_target() -> (u32, u32) {
from_set_deployment_target("IPHONEOS_DEPLOYMENT_TARGET").unwrap_or((7, 0))
}

fn mac_catalyst_deployment_target() -> (u32, u32) {
// If you are looking for the default deployment target, prefer `rustc --print deployment-target`.
from_set_deployment_target("IPHONEOS_DEPLOYMENT_TARGET").unwrap_or((14, 0))
}

pub fn ios_llvm_target(arch: Arch) -> String {
// Modern iOS tooling extracts information about deployment target
// from LC_BUILD_VERSION. This load command will only be emitted when
Expand Down
2 changes: 2 additions & 0 deletions compiler/rustc_target/src/spec/mod.rs
Original file line number Diff line number Diff line change
Expand Up @@ -61,6 +61,8 @@ mod aix_base;
mod android_base;
mod apple_base;
pub use apple_base::deployment_target as current_apple_deployment_target;
pub use apple_base::platform as current_apple_platform;
pub use apple_base::sdk_version as current_apple_sdk_version;
mod avr_gnu_base;
pub use avr_gnu_base::ef_avr_arch;
mod bpf_base;
Expand Down

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