Auto merge of #129369 - madsmtm:apple-cc-linker-pass-target, r=jieyouxu

Pass deployment target when linking with CC on Apple targets

This PR effectively implements what's also being considered in the `cc` crate [here](rust-lang/cc-rs#1030 (comment)), that is:
- When linking macOS targets with CC, pass the `-mmacosx-version-min=.` option to specify the desired deployment target. Also, no longer pass `-m32`/`-m64`, these are redundant since we already pass `-arch`.
- When linking with CC on iOS, tvOS, watchOS and visionOS, only pass `-target` (we assume for these targets that CC forwards to Clang).

This is required to get the linker to emit the correct `LC_BUILD_VERSION` of the final binary. See #129432 for more motivation behind this change.

r? compiler

CC `@BlackHoleFox`

compiler/rustc_target/src/spec/base/apple/mod.rs

@@ -168,14 +168,42 @@ fn pre_link_args(os: &'static str, arch: Arch, abi: TargetAbi) -> LinkArgs {
  ["-platform_version".into(), platform_name, min_version, sdk_version].into_iter(),
  );
 
- if abi != TargetAbi::MacCatalyst {
+ // We need to communicate four things to the C compiler to be able to link:
+ // - The architecture.
+ // - The operating system (and that it's an Apple platform).
+ // - The deployment target.
+ // - The environment / ABI.
+ //
+ // We'd like to use `-target` everywhere, since that can uniquely
+ // communicate all of these, but that doesn't work on GCC, and since we
+ // don't know whether the `cc` compiler is Clang, GCC, or something else,
+ // we fall back to other options that also work on GCC when compiling for
+ // macOS.
+ //
+ // Targets other than macOS are ill-supported by GCC (it doesn't even
+ // support e.g. `-miphoneos-version-min`), so in those cases we can fairly
+ // safely use `-target`. See also the following, where it is made explicit
+ // that the recommendation by LLVM developers is to use `-target`:
+ // <https://github.com/llvm/llvm-project/issues/88271>
+ if os == "macos" {
+ // `-arch` communicates the architecture.
+ //
  // CC forwards the `-arch` to the linker, so we use the same value
  // here intentionally.
  add_link_args(
  &mut args,
  LinkerFlavor::Darwin(Cc::Yes, Lld::No),
  &["-arch", arch.ld_arch()],
  );
+ // The presence of `-mmacosx-version-min` makes CC default to macOS,
+ // and it sets the deployment target.
+ let (major, minor, patch) = deployment_target(os, arch, abi);
+ let opt = format!("-mmacosx-version-min={major}.{minor}.{patch}").into();
+ add_link_args_iter(&mut args, LinkerFlavor::Darwin(Cc::Yes, Lld::No), [opt].into_iter());
+ // macOS has no environment, so with these two, we've told CC all the
+ // desired parameters.
+ //
+ // We avoid `-m32`/`-m64`, as this is already encoded by `-arch`.
  } else {
  add_link_args_iter(
  &mut args,

compiler/rustc_target/src/spec/targets/i686_apple_darwin.rs

@@ -1,10 +1,8 @@
 use crate::spec::base::apple::{base, Arch, TargetAbi};
-use crate::spec::{Cc, FramePointer, LinkerFlavor, Lld, Target, TargetOptions};
+use crate::spec::{FramePointer, Target, TargetOptions};
 
 pub(crate) fn target() -> Target {
- let (mut opts, llvm_target, arch) = base("macos", Arch::I686, TargetAbi::Normal);
- opts.add_pre_link_args(LinkerFlavor::Darwin(Cc::Yes, Lld::No), &["-m32"]);
-
+ let (opts, llvm_target, arch) = base("macos", Arch::I686, TargetAbi::Normal);
  Target {
  llvm_target,
  metadata: crate::spec::TargetMetadata {

compiler/rustc_target/src/spec/targets/x86_64_apple_darwin.rs

@@ -1,9 +1,8 @@
 use crate::spec::base::apple::{base, Arch, TargetAbi};
-use crate::spec::{Cc, FramePointer, LinkerFlavor, Lld, SanitizerSet, Target, TargetOptions};
+use crate::spec::{FramePointer, SanitizerSet, Target, TargetOptions};
 
 pub(crate) fn target() -> Target {
- let (mut opts, llvm_target, arch) = base("macos", Arch::X86_64, TargetAbi::Normal);
- opts.add_pre_link_args(LinkerFlavor::Darwin(Cc::Yes, Lld::No), &["-m64"]);
+ let (opts, llvm_target, arch) = base("macos", Arch::X86_64, TargetAbi::Normal);
  Target {
  llvm_target,
  metadata: crate::spec::TargetMetadata {

compiler/rustc_target/src/spec/targets/x86_64h_apple_darwin.rs

@@ -1,11 +1,10 @@
 use crate::spec::base::apple::{base, Arch, TargetAbi};
-use crate::spec::{Cc, FramePointer, LinkerFlavor, Lld, SanitizerSet, Target, TargetOptions};
+use crate::spec::{FramePointer, SanitizerSet, Target, TargetOptions};
 
 pub(crate) fn target() -> Target {
  let (mut opts, llvm_target, arch) = base("macos", Arch::X86_64h, TargetAbi::Normal);
  opts.max_atomic_width = Some(128);
  opts.frame_pointer = FramePointer::Always;
- opts.add_pre_link_args(LinkerFlavor::Darwin(Cc::Yes, Lld::No), &["-m64"]);
  opts.supported_sanitizers =
  SanitizerSet::ADDRESS | SanitizerSet::CFI | SanitizerSet::LEAK | SanitizerSet::THREAD;
 

tests/run-make/apple-deployment-target/rmake.rs

@@ -81,9 +81,8 @@ fn main() {
  rustc().env(env_var, example_version).run();
  minos("libfoo.dylib", example_version);
 
- // FIXME(madsmtm): Deployment target is not currently passed properly to linker
- // rustc().env_remove(env_var).run();
- // minos("libfoo.dylib", default_version);
+ rustc().env_remove(env_var).run();
+ minos("libfoo.dylib", default_version);
 
  // Test with ld64 instead
 
@@ -110,9 +109,8 @@ fn main() {
  rustc().env(env_var, example_version).run();
  minos("foo", example_version);
 
- // FIXME(madsmtm): Deployment target is not currently passed properly to linker
- // rustc().env_remove(env_var).run();
- // minos("foo", default_version);
+ rustc().env_remove(env_var).run();
+ minos("foo", default_version);
  }
 
  // Test with ld64 instead