Rollup merge of #143446 - usamoi:export-executable-symbols, r=bjorn3,oli-obk

use `--dynamic-list` for exporting executable symbols

closes rust-lang/rust#101610
cc rust-lang/rust#84161

https://sourceware.org/binutils/docs-2.39/ld/VERSION.html:

> --dynamic-list=dynamic-list-file
Specify the name of a dynamic list file to the linker. This is typically used when creating shared libraries to specify a list of global symbols whose references shouldn’t be bound to the definition within the shared library, or creating dynamically linked executables to specify a list of symbols which should be added to the symbol table in the executable. This option is only meaningful on ELF platforms which support shared libraries.

`ld.lld --help`:

>   --dynamic-list=<file>: Similar to --export-dynamic-symbol-list. When creating a shared object, this additionally implies -Bsymbolic but does not set DF_SYMBOLIC

>  --export-dynamic-symbol-list=file: Read a list of dynamic symbol patterns. Apply --export-dynamic-symbol on each pattern

>  --export-dynamic-symbol=glob: (executable) Put matched symbols in the dynamic symbol table. (shared object) References to matched non-local STV_DEFAULT symbols shouldn't be bound to definitions within the shared object. Does not imply -Bsymbolic.

>  --export-dynamic: Put symbols in the dynamic symbol table

Use `--dynamic-list` because it's older than `--export-dynamic-symbol-list` (binutils 2.35)

try-job: dist-i586-gnu-i586-i686-musl

compiler/rustc_codegen_ssa/src/back/linker.rs

@@ -800,9 +800,7 @@ impl<'a> Linker for GccLinker<'a> {
             return;
         }
 
-        let is_windows = self.sess.target.is_like_windows;
-        let path = tmpdir.join(if is_windows { "list.def" } else { "list" });
-
+        let path = tmpdir.join(if self.sess.target.is_like_windows { "list.def" } else { "list" });
         debug!("EXPORTED SYMBOLS:");
 
         if self.sess.target.is_like_darwin {
@@ -817,7 +815,8 @@ impl<'a> Linker for GccLinker<'a> {
             if let Err(error) = res {
                 self.sess.dcx().emit_fatal(errors::LibDefWriteFailure { error });
             }
-        } else if is_windows {
+            self.link_arg("-exported_symbols_list").link_arg(path);
+        } else if self.sess.target.is_like_windows {
             let res: io::Result<()> = try {
                 let mut f = File::create_buffered(&path)?;
 
@@ -835,6 +834,21 @@ impl<'a> Linker for GccLinker<'a> {
             if let Err(error) = res {
                 self.sess.dcx().emit_fatal(errors::LibDefWriteFailure { error });
             }
+            self.link_arg(path);
+        } else if crate_type == CrateType::Executable && !self.sess.target.is_like_solaris {
+            let res: io::Result<()> = try {
+                let mut f = File::create_buffered(&path)?;
+                writeln!(f, "{{")?;
+                for (sym, _) in symbols {
+                    debug!(sym);
+                    writeln!(f, "  {sym};")?;
+                }
+                writeln!(f, "}};")?;
+            };
+            if let Err(error) = res {
+                self.sess.dcx().emit_fatal(errors::VersionScriptWriteFailure { error });
+            }
+            self.link_arg("--dynamic-list").link_arg(path);
         } else {
             // Write an LD version script
             let res: io::Result<()> = try {
@@ -852,20 +866,15 @@ impl<'a> Linker for GccLinker<'a> {
             if let Err(error) = res {
                 self.sess.dcx().emit_fatal(errors::VersionScriptWriteFailure { error });
             }
-        }
-
-        if self.sess.target.is_like_darwin {
-            self.link_arg("-exported_symbols_list").link_arg(path);
-        } else if self.sess.target.is_like_solaris {
+            if self.sess.target.is_like_solaris {
                 self.link_arg("-M").link_arg(path);
-        } else if is_windows {
-            self.link_arg(path);
             } else {
                 let mut arg = OsString::from("--version-script=");
                 arg.push(path);
                 self.link_arg(arg).link_arg("--no-undefined-version");
             }
         }
+    }
 
     fn subsystem(&mut self, subsystem: &str) {
         self.link_args(&["--subsystem", subsystem]);

tests/ui/linking/export-executable-symbols.rs

@@ -0,0 +1,30 @@
+//@ run-pass
+//@ only-linux
+//@ only-gnu
+//@ compile-flags: -Zexport-executable-symbols
+//@ edition: 2024
+
+// Regression test for <https://github.com/rust-lang/rust/issues/101610>.
+
+#![feature(rustc_private)]
+
+extern crate libc;
+
+#[unsafe(no_mangle)]
+fn hack() -> u64 {
+    998244353
+}
+
+fn main() {
+    unsafe {
+        let handle = libc::dlopen(std::ptr::null(), libc::RTLD_NOW);
+        let ptr = libc::dlsym(handle, c"hack".as_ptr());
+        let ptr: Option<unsafe fn() -> u64> = std::mem::transmute(ptr);
+        if let Some(f) = ptr {
+            assert!(f() == 998244353);
+            println!("symbol `hack` is found successfully");
+        } else {
+            panic!("symbol `hack` is not found");
+        }
+    }
+}