Rollup merge of rust-lang#59752 - Zoxc:dylib-fix, r=michaelwoerister

Limit dylib symbols

This makes `windows-gnu` match the behavior of `windows-msvc`. It probably doesn't make sense to export these symbols on other platforms either.

Author: Centril

src/librustc_codegen_ssa/back/linker.rs

@@ -372,25 +372,18 @@ impl<'a> Linker for GccLinker<'a> {
     }
 
     fn export_symbols(&mut self, tmpdir: &Path, crate_type: CrateType) {
-        // If we're compiling a dylib, then we let symbol visibility in object
-        // files to take care of whether they're exported or not.
-        //
-        // If we're compiling a cdylib, however, we manually create a list of
-        // exported symbols to ensure we don't expose any more. The object files
-        // have far more public symbols than we actually want to export, so we
-        // hide them all here.
-        if crate_type == CrateType::Dylib ||
-           crate_type == CrateType::ProcMacro {
-            return
-        }
+        // We manually create a list of exported symbols to ensure we don't expose any more.
+        // The object files have far more public symbols than we actually want to export,
+        // so we hide them all here.
 
-        // Symbol visibility takes care of this for the WebAssembly.
-        // Additionally the only known linker, LLD, doesn't support the script
-        // arguments just yet
-        if self.sess.target.target.arch == "wasm32" {
+        if !self.sess.target.target.options.limit_rdylib_exports {
             return;
         }
 
+        if crate_type == CrateType::ProcMacro {
+            return
+        }
+
         let mut arg = OsString::new();
         let path = tmpdir.join("list");
 

src/librustc_target/spec/mod.rs

@@ -751,6 +751,9 @@ pub struct TargetOptions {
     /// wasm32 where the whole program either has simd or not.
     pub simd_types_indirect: bool,
 
+    /// Pass a list of symbol which should be exported in the dylib to the linker.
+    pub limit_rdylib_exports: bool,
+
     /// If set, have the linker export exactly these symbols, instead of using
     /// the usual logic to figure this out from the crate itself.
     pub override_export_symbols: Option<Vec<String>>,
@@ -846,6 +849,7 @@ impl Default for TargetOptions {
             emit_debug_gdb_scripts: true,
             requires_uwtable: false,
             simd_types_indirect: true,
+            limit_rdylib_exports: true,
             override_export_symbols: None,
             merge_functions: MergeFunctions::Aliases,
             target_mcount: "mcount".to_string(),
@@ -1152,6 +1156,7 @@ impl Target {
         key!(emit_debug_gdb_scripts, bool);
         key!(requires_uwtable, bool);
         key!(simd_types_indirect, bool);
+        key!(limit_rdylib_exports, bool);
         key!(override_export_symbols, opt_list);
         key!(merge_functions, MergeFunctions)?;
         key!(target_mcount);
@@ -1367,6 +1372,7 @@ impl ToJson for Target {
         target_option_val!(emit_debug_gdb_scripts);
         target_option_val!(requires_uwtable);
         target_option_val!(simd_types_indirect);
+        target_option_val!(limit_rdylib_exports);
         target_option_val!(override_export_symbols);
         target_option_val!(merge_functions);
         target_option_val!(target_mcount);

src/librustc_target/spec/solaris_base.rs

@@ -8,6 +8,7 @@ pub fn opts() -> TargetOptions {
         has_rpath: true,
         target_family: Some("unix".to_string()),
         is_like_solaris: true,
+        limit_rdylib_exports: false, // Linker doesn't support this
 
         .. Default::default()
     }

src/librustc_target/spec/wasm32_base.rs

@@ -106,6 +106,11 @@ pub fn options() -> TargetOptions {
         // no dynamic linking, no need for default visibility!
         default_hidden_visibility: true,
 
+        // Symbol visibility takes care of this for the WebAssembly.
+        // Additionally the only known linker, LLD, doesn't support the script
+        // arguments just yet
+        limit_rdylib_exports: false,
+
         // we use the LLD shipped with the Rust toolchain by default
         linker: Some("rust-lld".to_owned()),
         lld_flavor: LldFlavor::Wasm,

src/librustc_target/spec/wasm32_experimental_emscripten.rs

@@ -24,6 +24,7 @@ pub fn target() -> Result<Target, String> {
         is_like_emscripten: true,
         max_atomic_width: Some(32),
         post_link_args,
+        limit_rdylib_exports: false,
         target_family: Some("unix".to_string()),
         .. Default::default()
     };

src/librustc_target/spec/wasm32_unknown_emscripten.rs

@@ -26,6 +26,7 @@ pub fn target() -> Result<Target, String> {
         is_like_emscripten: true,
         max_atomic_width: Some(32),
         post_link_args,
+        limit_rdylib_exports: false,
         target_family: Some("unix".to_string()),
         codegen_backend: "emscripten".to_string(),
         .. Default::default()