Rollup merge of #143482 - ia0:fix, r=fee1-dead

Fix short linker error output

This PR does 2 things:

- It removes the braces when there's a single element. This is required since brace expansion (at least in bash and zsh) only triggers if there's at least 2 elements.

- It removes the extra `.rlib` suffixes of the elements. See https://github.com/rust-lang/rust/pull/135707#discussion_r2185212393 for context.

Running `cargo +stage1 build` on the following program:

```rust
unsafe extern "C" {
    fn foo() -> libc::c_int;
}

fn main() {
    let x = unsafe { foo() } as u32;
    // println!("{}", data_encoding::BASE64.encode(&x.to_le_bytes()));
}
```

Gives the following diff before and after the PR:

```diff
-/tmp/foo/target/debug/deps/{liblibc-faf416f178830595.rlib}.rlib
+/tmp/foo/target/debug/deps/liblibc-faf416f178830595.rlib
```

Running on the same program with the additional dependency, we get the following diff:

```diff
-/tmp/foo/target/debug/deps/{liblibc-faf416f178830595.rlib,libdata_encoding-84bb5aadfa9e8839.rlib}.rlib
+/tmp/foo/target/debug/deps/{liblibc-faf416f178830595,libdata_encoding-84bb5aadfa9e8839}.rlib
```

compiler/rustc_codegen_ssa/src/errors.rs

@@ -457,7 +457,7 @@ impl<G: EmissionGuarantee> Diagnostic<'_, G> for LinkingFailed<'_> {
                 } else if arg.as_encoded_bytes().ends_with(b".rlib") {
                     let rlib_path = Path::new(&arg);
                     let dir = rlib_path.parent().unwrap();
-                    let filename = rlib_path.file_name().unwrap().to_owned();
+                    let filename = rlib_path.file_stem().unwrap().to_owned();
                     if let Some(ArgGroup::Rlibs(parent, rlibs)) = args.last_mut() {
                         if parent == dir {
                             rlibs.push(filename);
@@ -471,7 +471,7 @@ impl<G: EmissionGuarantee> Diagnostic<'_, G> for LinkingFailed<'_> {
                     args.push(ArgGroup::Regular(arg));
                 }
             }
-            let crate_hash = regex::bytes::Regex::new(r"-[0-9a-f]+\.rlib$").unwrap();
+            let crate_hash = regex::bytes::Regex::new(r"-[0-9a-f]+").unwrap();
             self.command.args(args.into_iter().map(|arg_group| {
                 match arg_group {
                     // SAFETY: we are only matching on ASCII, not any surrogate pairs, so any replacements we do will still be valid.
@@ -494,7 +494,11 @@ impl<G: EmissionGuarantee> Diagnostic<'_, G> for LinkingFailed<'_> {
                             Err(_) => false,
                         };
                         let mut arg = dir.into_os_string();
-                        arg.push("/{");
+                        arg.push("/");
+                        let needs_braces = rlibs.len() >= 2;
+                        if needs_braces {
+                            arg.push("{");
+                        }
                         let mut first = true;
                         for mut rlib in rlibs {
                             if !first {
@@ -513,7 +517,10 @@ impl<G: EmissionGuarantee> Diagnostic<'_, G> for LinkingFailed<'_> {
                             }
                             arg.push(rlib);
                         }
-                        arg.push("}.rlib");
+                        if needs_braces {
+                            arg.push("}");
+                        }
+                        arg.push(".rlib");
                         arg
                     }
                 }

tests/run-make/linker-warning/bar.rs

@@ -0,0 +1,2 @@
+#[repr(C)]
+pub struct Bar(u32);

tests/run-make/linker-warning/foo.rs

@@ -0,0 +1,2 @@
+#[repr(C)]
+pub struct Foo(u32);

tests/run-make/linker-warning/main.rs

@@ -1 +1,10 @@
-fn main() {}
+unsafe extern "C" {
+    #[cfg(only_foo)]
+    fn does_not_exist(p: *const u8) -> *const foo::Foo;
+    #[cfg(not(only_foo))]
+    fn does_not_exist(p: *const bar::Bar) -> *const foo::Foo;
+}
+
+fn main() {
+    let _ = unsafe { does_not_exist(core::ptr::null()) };
+}

tests/run-make/linker-warning/rmake.rs

@@ -11,6 +11,7 @@ fn run_rustc() -> Rustc {
         .arg("-Clink-self-contained=-linker")
         .arg("-Zunstable-options")
         .arg("-Wlinker-messages")
+        .args(["--extern", "foo", "--extern", "bar"])
         .output("main")
         .linker("./fake-linker");
     if run_make_support::target() == "x86_64-unknown-linux-gnu" {
@@ -21,8 +22,10 @@ fn run_rustc() -> Rustc {
 }
 
 fn main() {
-    // first, compile our linker
+    // first, compile our linker and our dependencies
     rustc().arg("fake-linker.rs").output("fake-linker").run();
+    rustc().arg("foo.rs").crate_type("rlib").run();
+    rustc().arg("bar.rs").crate_type("rlib").run();
 
     // Run rustc with our fake linker, and make sure it shows warnings
     let warnings = run_rustc().link_arg("run_make_warn").run();
@@ -48,7 +51,8 @@ fn main() {
     let out = run_rustc().link_arg("run_make_error").run_fail();
     out.assert_stderr_contains("fake-linker")
         .assert_stderr_contains("object files omitted")
-        .assert_stderr_contains_regex(r"\{")
+        .assert_stderr_contains("/{libfoo,libbar}.rlib\"")
+        .assert_stderr_contains("-*}.rlib\"")
         .assert_stderr_not_contains(r".rcgu.o")
         .assert_stderr_not_contains_regex(r"lib(/|\\\\)libstd");
 
@@ -68,6 +72,10 @@ fn main() {
             .run();
     }
 
+    // Make sure a single dependency doesn't use brace expansion.
+    let out1 = run_rustc().cfg("only_foo").link_arg("run_make_error").run_fail();
+    out1.assert_stderr_contains("fake-linker").assert_stderr_contains("/libfoo.rlib\"");
+
     // Make sure we show linker warnings even across `-Z no-link`
     rustc()
         .arg("-Zno-link")

tests/run-make/linker-warning/short-error.txt

@@ -1,6 +1,6 @@
 error: linking with `./fake-linker` failed: exit status: 1
   |
-  = note:  "./fake-linker" "-m64" "/symbols.o" "<2 object files omitted>" "-Wl,--as-needed" "-Wl,-Bstatic" "<sysroot>/lib/rustlib/x86_64-unknown-linux-gnu/lib/{libstd-*,libpanic_unwind-*,libobject-*,libmemchr-*,libaddr2line-*,libgimli-*,librustc_demangle-*,libstd_detect-*,libhashbrown-*,librustc_std_workspace_alloc-*,libminiz_oxide-*,libadler2-*,libunwind-*,libcfg_if-*,liblibc-*,librustc_std_workspace_core-*,liballoc-*,libcore-*,libcompiler_builtins-*}.rlib" "-Wl,-Bdynamic" "-lgcc_s" "-lutil" "-lrt" "-lpthread" "-lm" "-ldl" "-lc" "-L" "/raw-dylibs" "-Wl,--eh-frame-hdr" "-Wl,-z,noexecstack" "-L" "/build-root/test/run-make/linker-warning/rmake_out" "-L" "<sysroot>/lib/rustlib/x86_64-unknown-linux-gnu/lib" "-o" "main" "-Wl,--gc-sections" "-pie" "-Wl,-z,relro,-z,now" "-nodefaultlibs" "run_make_error"
+  = note:  "./fake-linker" "-m64" "/symbols.o" "<2 object files omitted>" "-Wl,--as-needed" "-Wl,-Bstatic" "/build-root/test/run-make/linker-warning/rmake_out/{libfoo,libbar}.rlib" "<sysroot>/lib/rustlib/x86_64-unknown-linux-gnu/lib/{libstd-*,libpanic_unwind-*,libobject-*,libmemchr-*,libaddr2line-*,libgimli-*,librustc_demangle-*,libstd_detect-*,libhashbrown-*,librustc_std_workspace_alloc-*,libminiz_oxide-*,libadler2-*,libunwind-*,libcfg_if-*,liblibc-*,librustc_std_workspace_core-*,liballoc-*,libcore-*,libcompiler_builtins-*}.rlib" "-Wl,-Bdynamic" "-lgcc_s" "-lutil" "-lrt" "-lpthread" "-lm" "-ldl" "-lc" "-L" "/raw-dylibs" "-Wl,--eh-frame-hdr" "-Wl,-z,noexecstack" "-L" "/build-root/test/run-make/linker-warning/rmake_out" "-L" "<sysroot>/lib/rustlib/x86_64-unknown-linux-gnu/lib" "-o" "main" "-Wl,--gc-sections" "-pie" "-Wl,-z,relro,-z,now" "-nodefaultlibs" "run_make_error"
   = note: some arguments are omitted. use `--verbose` to show all linker arguments
   = note: error: baz