Return just the target name from the ELF linker's link functions

link returned a LinkResult, Result<i32, &str>: an exit status, or the
target the inputs are actually for. The status was always 0, as a link
that fails exits in the middle, so link now returns Option<&str>, the
other target if there is one, and the driver returns nothing.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

arch/elf-arm32/lib.rs

@@ -1,3 +1,3 @@
-pub fn link(cmdline: mold_elf::driver::Cmdline) -> mold_elf::driver::LinkResult {
+pub fn link(cmdline: mold_elf::driver::Cmdline) -> Option<&'static str> {
     mold_elf::driver::link::<mold_elf::arch::Arm32>(cmdline)
 }

arch/elf-arm32be/lib.rs

@@ -1,3 +1,3 @@
-pub fn link(cmdline: mold_elf::driver::Cmdline) -> mold_elf::driver::LinkResult {
+pub fn link(cmdline: mold_elf::driver::Cmdline) -> Option<&'static str> {
     mold_elf::driver::link::<mold_elf::arch::Arm32Be>(cmdline)
 }

arch/elf-arm64/lib.rs

@@ -1,3 +1,3 @@
-pub fn link(cmdline: mold_elf::driver::Cmdline) -> mold_elf::driver::LinkResult {
+pub fn link(cmdline: mold_elf::driver::Cmdline) -> Option<&'static str> {
     mold_elf::driver::link::<mold_elf::arch::Arm64>(cmdline)
 }

arch/elf-arm64be/lib.rs

@@ -1,3 +1,3 @@
-pub fn link(cmdline: mold_elf::driver::Cmdline) -> mold_elf::driver::LinkResult {
+pub fn link(cmdline: mold_elf::driver::Cmdline) -> Option<&'static str> {
     mold_elf::driver::link::<mold_elf::arch::Arm64Be>(cmdline)
 }

arch/elf-i386/lib.rs

@@ -1,3 +1,3 @@
-pub fn link(cmdline: mold_elf::driver::Cmdline) -> mold_elf::driver::LinkResult {
+pub fn link(cmdline: mold_elf::driver::Cmdline) -> Option<&'static str> {
     mold_elf::driver::link::<mold_elf::arch::I386>(cmdline)
 }

arch/elf-loongarch32/lib.rs

@@ -1,3 +1,3 @@
-pub fn link(cmdline: mold_elf::driver::Cmdline) -> mold_elf::driver::LinkResult {
+pub fn link(cmdline: mold_elf::driver::Cmdline) -> Option<&'static str> {
     mold_elf::driver::link::<mold_elf::arch::LoongArch32>(cmdline)
 }

arch/elf-loongarch64/lib.rs

@@ -1,3 +1,3 @@
-pub fn link(cmdline: mold_elf::driver::Cmdline) -> mold_elf::driver::LinkResult {
+pub fn link(cmdline: mold_elf::driver::Cmdline) -> Option<&'static str> {
     mold_elf::driver::link::<mold_elf::arch::LoongArch64>(cmdline)
 }

arch/elf-m68k/lib.rs

@@ -1,3 +1,3 @@
-pub fn link(cmdline: mold_elf::driver::Cmdline) -> mold_elf::driver::LinkResult {
+pub fn link(cmdline: mold_elf::driver::Cmdline) -> Option<&'static str> {
     mold_elf::driver::link::<mold_elf::arch::M68k>(cmdline)
 }

arch/elf-ppc32/lib.rs

@@ -1,3 +1,3 @@
-pub fn link(cmdline: mold_elf::driver::Cmdline) -> mold_elf::driver::LinkResult {
+pub fn link(cmdline: mold_elf::driver::Cmdline) -> Option<&'static str> {
     mold_elf::driver::link::<mold_elf::arch::Ppc32>(cmdline)
 }

arch/elf-ppc64v1/lib.rs

@@ -1,3 +1,3 @@
-pub fn link(cmdline: mold_elf::driver::Cmdline) -> mold_elf::driver::LinkResult {
+pub fn link(cmdline: mold_elf::driver::Cmdline) -> Option<&'static str> {
     mold_elf::driver::link::<mold_elf::arch::Ppc64V1>(cmdline)
 }

arch/elf-ppc64v2/lib.rs

@@ -1,3 +1,3 @@
-pub fn link(cmdline: mold_elf::driver::Cmdline) -> mold_elf::driver::LinkResult {
+pub fn link(cmdline: mold_elf::driver::Cmdline) -> Option<&'static str> {
     mold_elf::driver::link::<mold_elf::arch::Ppc64V2>(cmdline)
 }

arch/elf-riscv32/lib.rs

@@ -1,3 +1,3 @@
-pub fn link(cmdline: mold_elf::driver::Cmdline) -> mold_elf::driver::LinkResult {
+pub fn link(cmdline: mold_elf::driver::Cmdline) -> Option<&'static str> {
     mold_elf::driver::link::<mold_elf::arch::Riscv32>(cmdline)
 }

arch/elf-riscv32be/lib.rs

@@ -1,3 +1,3 @@
-pub fn link(cmdline: mold_elf::driver::Cmdline) -> mold_elf::driver::LinkResult {
+pub fn link(cmdline: mold_elf::driver::Cmdline) -> Option<&'static str> {
     mold_elf::driver::link::<mold_elf::arch::Riscv32Be>(cmdline)
 }

arch/elf-riscv64/lib.rs

@@ -1,3 +1,3 @@
-pub fn link(cmdline: mold_elf::driver::Cmdline) -> mold_elf::driver::LinkResult {
+pub fn link(cmdline: mold_elf::driver::Cmdline) -> Option<&'static str> {
     mold_elf::driver::link::<mold_elf::arch::Riscv64>(cmdline)
 }

arch/elf-riscv64be/lib.rs

@@ -1,3 +1,3 @@
-pub fn link(cmdline: mold_elf::driver::Cmdline) -> mold_elf::driver::LinkResult {
+pub fn link(cmdline: mold_elf::driver::Cmdline) -> Option<&'static str> {
     mold_elf::driver::link::<mold_elf::arch::Riscv64Be>(cmdline)
 }

arch/elf-s390x/lib.rs

@@ -1,3 +1,3 @@
-pub fn link(cmdline: mold_elf::driver::Cmdline) -> mold_elf::driver::LinkResult {
+pub fn link(cmdline: mold_elf::driver::Cmdline) -> Option<&'static str> {
     mold_elf::driver::link::<mold_elf::arch::S390x>(cmdline)
 }

arch/elf-sh4/lib.rs

@@ -1,3 +1,3 @@
-pub fn link(cmdline: mold_elf::driver::Cmdline) -> mold_elf::driver::LinkResult {
+pub fn link(cmdline: mold_elf::driver::Cmdline) -> Option<&'static str> {
     mold_elf::driver::link::<mold_elf::arch::Sh4>(cmdline)
 }

arch/elf-sh4be/lib.rs

@@ -1,3 +1,3 @@
-pub fn link(cmdline: mold_elf::driver::Cmdline) -> mold_elf::driver::LinkResult {
+pub fn link(cmdline: mold_elf::driver::Cmdline) -> Option<&'static str> {
     mold_elf::driver::link::<mold_elf::arch::Sh4Be>(cmdline)
 }

arch/elf-sparc64/lib.rs

@@ -1,3 +1,3 @@
-pub fn link(cmdline: mold_elf::driver::Cmdline) -> mold_elf::driver::LinkResult {
+pub fn link(cmdline: mold_elf::driver::Cmdline) -> Option<&'static str> {
     mold_elf::driver::link::<mold_elf::arch::Sparc64>(cmdline)
 }

arch/elf-x86_64/lib.rs

@@ -1,3 +1,3 @@
-pub fn link(cmdline: mold_elf::driver::Cmdline) -> mold_elf::driver::LinkResult {
+pub fn link(cmdline: mold_elf::driver::Cmdline) -> Option<&'static str> {
     mold_elf::driver::link::<mold_elf::arch::X86_64>(cmdline)
 }

cli/main.rs

@@ -11,7 +11,7 @@
 // the speed of unwinding, so we keep rustc from reporting it.
 #![cfg_attr(all(target_vendor = "apple", debug_assertions), allow(linker_messages))]
 
-use mold_elf::driver::{Cmdline, LinkResult};
+use mold_elf::driver::Cmdline;
 use std::ffi::OsStr;
 use std::path::Path;
 
@@ -21,7 +21,7 @@ use std::path::Path;
 #[global_allocator]
 static GLOBAL: mimalloc::MiMalloc = mimalloc::MiMalloc;
 
-type LinkFn = fn(Cmdline) -> LinkResult;
+type LinkFn = fn(Cmdline) -> Option<&'static str>;
 type MachoLinkFn = fn(mold_macho::driver::ParsedArgs);
 
 // Each target has its own monomorphized link function. The ELF linker
@@ -110,5 +110,6 @@ fn main() {
         std::process::exit(1);
     };
     let link = |target: &str, cmdline| link_fn(ELF_TARGETS, target)(cmdline);
-    std::process::exit(mold_elf::driver::main(args, initial_target, link));
+    mold_elf::driver::main(args, initial_target, link);
+    std::process::exit(0);
 }

elf/driver.rs

@@ -21,21 +21,18 @@ use crate::passes;
 /// that report it.
 pub type Cmdline = Arc<[Cow<'static, OsStr>]>;
 
-/// The exit status of a link, or the name of the target the inputs are
-/// actually for.
-pub type LinkResult = Result<i32, &'static str>;
-
-/// Runs the linker with the given command line. Returns the exit status.
+/// Runs the linker with the given command line. A link that fails exits
+/// in the middle (see mold_common::error::checkpoint).
 ///
 /// `initial_target` is an enabled target used for the initial argument
-/// parsing. `link_for_target` links for a named target, or reports the
+/// parsing. `link_for_target` links for a named target, or returns the
 /// target the inputs are actually for; the executable provides both, as
 /// the targets are instantiated in crates of their own.
 pub fn main(
     argv: Vec<OsString>,
     initial_target: &str,
-    link_for_target: impl Fn(&str, Cmdline) -> LinkResult,
-) -> i32 {
+    link_for_target: impl Fn(&str, Cmdline) -> Option<&'static str>,
+) {
     // A parent's transparent huge page disable flag is inherited. Restore
     // the system's default policy so large links can use huge pages.
     #[cfg(any(target_os = "android", target_os = "linux"))]
@@ -65,8 +62,8 @@ pub fn main(
             let _ = std::env::set_current_dir(cwd);
         }
         match link_for_target(target, Arc::clone(&cmdline)) {
-            Ok(status) => return status,
-            Err(actual) => target = actual,
+            Some(actual) => target = actual,
+            None => return,
         }
     }
 }
@@ -81,9 +78,9 @@ fn thread_count(args: &Args) -> usize {
         .unwrap_or_else(|| std::thread::available_parallelism().map_or(1, |n| n.get()).min(32))
 }
 
-/// Links for the target `E`, or reports the target the inputs are actually
-/// for.
-pub fn link<E: Target>(cmdline: Cmdline) -> LinkResult {
+/// Links for the target `E`, or returns the target the inputs are
+/// actually for.
+pub fn link<E: Target>(cmdline: Cmdline) -> Option<&'static str> {
     let parsed = cmdline::parse_args(&target_traits::<E>(), &cmdline);
     let cmdline::ParsedArgs { args, jobs, .. } = parsed;
     let mut ctx = Context::<E>::new(args, cmdline);
@@ -95,7 +92,7 @@ pub fn link<E: Target>(cmdline: Cmdline) -> LinkResult {
 
     // Redo if -m does not match our speculation.
     if ctx.args.emulation != E::NAME {
-        return Err(ctx.args.emulation);
+        return Some(ctx.args.emulation);
     }
 
     let t_all = ctx.timer("all");
@@ -234,7 +231,7 @@ pub fn link<E: Target>(cmdline: Cmdline) -> LinkResult {
     // in a separate file.
     if ctx.args.relocatable {
         crate::relocatable::combine_objects(&mut ctx);
-        return Ok(0);
+        return None;
     }
 
     // Create .bss sections for common symbols.
@@ -627,7 +624,7 @@ pub fn link<E: Target>(cmdline: Cmdline) -> LinkResult {
         error::exit_after_cleanup(0);
     }
     error::checkpoint();
-    Ok(0)
+    None
 }
 
 /// Opens the output file that the command line names.