Enable windows-gnu target to link to libgcc dynamically.

compiler/rustc_codegen_ssa/src/back/link.rs

@@ -1625,26 +1625,7 @@ fn add_user_defined_link_args(cmd: &mut dyn Linker, sess: &Session) {
 
 /// Add arbitrary "late link" args defined by the target spec.
 /// FIXME: Determine where exactly these args need to be inserted.
-fn add_late_link_args(
-    cmd: &mut dyn Linker,
-    sess: &Session,
-    flavor: LinkerFlavor,
-    crate_type: CrateType,
-    codegen_results: &CodegenResults,
-) {
-    let any_dynamic_crate = crate_type == CrateType::Dylib
-        || codegen_results.crate_info.dependency_formats.iter().any(|(ty, list)| {
-            *ty == crate_type && list.iter().any(|&linkage| linkage == Linkage::Dynamic)
-        });
-    if any_dynamic_crate {
-        if let Some(args) = sess.target.late_link_args_dynamic.get(&flavor) {
-            cmd.args(args);
-        }
-    } else {
-        if let Some(args) = sess.target.late_link_args_static.get(&flavor) {
-            cmd.args(args);
-        }
-    }
+fn add_late_link_args(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor) {
     if let Some(args) = sess.target.late_link_args.get(&flavor) {
         cmd.args(args);
     }
@@ -1870,7 +1851,7 @@ fn linker_with_args<'a, B: ArchiveBuilder<'a>>(
     // FIXME: Built-in target specs occasionally use this for linking system libraries,
     // eliminate all such uses by migrating them to `#[link]` attributes in `lib(std,c,unwind)`
     // and remove the option.
-    add_late_link_args(cmd, sess, flavor, crate_type, codegen_results);
+    add_late_link_args(cmd, sess, flavor);
 
     // ------------ Arbitrary order-independent options ------------
 

compiler/rustc_target/src/spec/mod.rs

@@ -1077,12 +1077,6 @@ pub struct TargetOptions {
     /// user-defined but before post-link objects. Standard platform
     /// libraries that should be always be linked to, usually go here.
     pub late_link_args: LinkArgs,
-    /// Linker arguments used in addition to `late_link_args` if at least one
-    /// Rust dependency is dynamically linked.
-    pub late_link_args_dynamic: LinkArgs,
-    /// Linker arguments used in addition to `late_link_args` if aall Rust
-    /// dependencies are statically linked.
-    pub late_link_args_static: LinkArgs,
     /// Linker arguments that are unconditionally passed *after* any
     /// user-defined libraries.
     pub post_link_args: LinkArgs,
@@ -1416,8 +1410,6 @@ impl Default for TargetOptions {
             post_link_objects_fallback: Default::default(),
             crt_objects_fallback: None,
             late_link_args: LinkArgs::new(),
-            late_link_args_dynamic: LinkArgs::new(),
-            late_link_args_static: LinkArgs::new(),
             link_env: Vec::new(),
             link_env_remove: Vec::new(),
             archive_format: "gnu".to_string(),
@@ -1965,8 +1957,6 @@ impl Target {
         key!(crt_objects_fallback, crt_objects_fallback)?;
         key!(pre_link_args, link_args);
         key!(late_link_args, link_args);
-        key!(late_link_args_dynamic, link_args);
-        key!(late_link_args_static, link_args);
         key!(post_link_args, link_args);
         key!(link_script, optional);
         key!(link_env, env);
@@ -2204,8 +2194,6 @@ impl ToJson for Target {
         target_option_val!(crt_objects_fallback);
         target_option_val!(link_args - pre_link_args);
         target_option_val!(link_args - late_link_args);
-        target_option_val!(link_args - late_link_args_dynamic);
-        target_option_val!(link_args - late_link_args_static);
         target_option_val!(link_args - post_link_args);
         target_option_val!(link_script);
         target_option_val!(env - link_env);

compiler/rustc_target/src/spec/tests/tests_impl.rs

@@ -18,13 +18,7 @@ impl Target {
             self.lld_flavor == LldFlavor::Link,
         );
         assert_eq!(self.is_like_msvc, self.lld_flavor == LldFlavor::Link);
-        for args in &[
-            &self.pre_link_args,
-            &self.late_link_args,
-            &self.late_link_args_dynamic,
-            &self.late_link_args_static,
-            &self.post_link_args,
-        ] {
+        for args in &[&self.pre_link_args, &self.late_link_args, &self.post_link_args] {
             assert_eq!(
                 args.get(&LinkerFlavor::Msvc),
                 args.get(&LinkerFlavor::Lld(LldFlavor::Link)),

compiler/rustc_target/src/spec/windows_gnu_base.rs

@@ -17,8 +17,6 @@ pub fn opts() -> TargetOptions {
     );
 
     let mut late_link_args = LinkArgs::new();
-    let mut late_link_args_dynamic = LinkArgs::new();
-    let mut late_link_args_static = LinkArgs::new();
     // Order of `late_link_args*` was found through trial and error to work with various
     // mingw-w64 versions (not tested on the CI). It's expected to change from time to time.
     let mingw_libs = vec![
@@ -39,25 +37,6 @@ pub fn opts() -> TargetOptions {
     ];
     late_link_args.insert(LinkerFlavor::Gcc, mingw_libs.clone());
     late_link_args.insert(LinkerFlavor::Lld(LldFlavor::Ld), mingw_libs);
-    let dynamic_unwind_libs = vec![
-        // If any of our crates are dynamically linked then we need to use
-        // the shared libgcc_s-dw2-1.dll. This is required to support
-        // unwinding across DLL boundaries.
-        "-lgcc_s".to_string(),
-    ];
-    late_link_args_dynamic.insert(LinkerFlavor::Gcc, dynamic_unwind_libs.clone());
-    late_link_args_dynamic.insert(LinkerFlavor::Lld(LldFlavor::Ld), dynamic_unwind_libs);
-    let static_unwind_libs = vec![
-        // If all of our crates are statically linked then we can get away
-        // with statically linking the libgcc unwinding code. This allows
-        // binaries to be redistributed without the libgcc_s-dw2-1.dll
-        // dependency, but unfortunately break unwinding across DLL
-        // boundaries when unwinding across FFI boundaries.
-        "-lgcc_eh".to_string(),
-        "-l:libpthread.a".to_string(),
-    ];
-    late_link_args_static.insert(LinkerFlavor::Gcc, static_unwind_libs.clone());
-    late_link_args_static.insert(LinkerFlavor::Lld(LldFlavor::Ld), static_unwind_libs);
 
     TargetOptions {
         os: "windows".to_string(),
@@ -81,8 +60,8 @@ pub fn opts() -> TargetOptions {
         post_link_objects_fallback: crt_objects::post_mingw_fallback(),
         crt_objects_fallback: Some(CrtObjectsFallback::Mingw),
         late_link_args,
-        late_link_args_dynamic,
-        late_link_args_static,
+        crt_static_allows_dylibs: true,
+        crt_static_respected: true,
         abi_return_struct_as_int: true,
         emit_debug_gdb_scripts: false,
         requires_uwtable: true,

compiler/rustc_target/src/spec/windows_uwp_gnu_base.rs

@@ -6,8 +6,6 @@ pub fn opts() -> TargetOptions {
     // FIXME: This should be updated for the exception machinery changes from #67502
     // and inherit from `windows_gnu_base`, at least partially.
     let mut late_link_args = LinkArgs::new();
-    let late_link_args_dynamic = LinkArgs::new();
-    let late_link_args_static = LinkArgs::new();
     let mingw_libs = vec![
         //"-lwinstorecompat".to_string(),
         //"-lmingwex".to_string(),
@@ -30,8 +28,6 @@ pub fn opts() -> TargetOptions {
         executables: false,
         limit_rdylib_exports: false,
         late_link_args,
-        late_link_args_dynamic,
-        late_link_args_static,
 
         ..base
     }

library/unwind/Cargo.toml

@@ -24,11 +24,11 @@ cc = "1.0.69"
 
 [features]
 
-# Only applies for Linux and Fuchsia targets
+# Only applies for MinGW, Linux and Fuchsia targets
 # Static link to the in-tree build of llvm libunwind
 llvm-libunwind = []
 
-# Only applies for Linux and Fuchsia targets
+# Only applies for MinGW, Linux and Fuchsia targets
 # If crt-static is enabled, static link to `libunwind.a` provided by system
 # If crt-static is disabled, dynamic link to `libunwind.so` provided by system
 system-llvm-libunwind = []

library/unwind/src/lib.rs

@@ -83,6 +83,32 @@ extern "C" {}
 #[link(name = "gcc_s", cfg(not(target_feature = "crt-static")))]
 extern "C" {}
 
+#[cfg(all(
+    windows,
+    target_env = "gnu",
+    not(feature = "llvm-libunwind"),
+    not(feature = "system-llvm-libunwind")
+))]
+#[link(name = "gcc_eh", kind = "static", modifiers = "-bundle", cfg(target_feature = "crt-static"))]
+#[link(
+    name = "pthread",
+    kind = "static",
+    modifiers = "-bundle",
+    cfg(target_feature = "crt-static")
+)]
+#[link(name = "gcc_s", cfg(not(target_feature = "crt-static")))]
+extern "C" {}
+
+#[cfg(all(
+    windows,
+    target_env = "gnu",
+    not(feature = "llvm-libunwind"),
+    feature = "system-llvm-libunwind"
+))]
+#[link(name = "unwind", kind = "static", modifiers = "-bundle", cfg(target_feature = "crt-static"))]
+#[link(name = "unwind", cfg(not(target_feature = "crt-static")))]
+extern "C" {}
+
 #[cfg(all(target_vendor = "fortanix", target_env = "sgx"))]
 #[link(name = "unwind", kind = "static", modifiers = "-bundle")]
 extern "C" {}

src/test/run-make-fulldeps/foreign-exceptions/Makefile

@@ -4,7 +4,7 @@ all: foo
 	$(call RUN,foo)
 
 foo: foo.rs $(call NATIVE_STATICLIB,foo)
-	$(RUSTC) $< -lfoo $(EXTRARSCXXFLAGS)
+	$(RUSTC) $< -lfoo $(EXTRACXXFLAGS)
 
 $(TMPDIR)/libfoo.o: foo.cpp
 	$(call COMPILE_OBJ_CXX,$@,$<)

src/test/run-make-fulldeps/tools.mk

@@ -105,28 +105,11 @@ ifdef IS_MSVC
 else
 	EXTRACFLAGS := -lws2_32 -luserenv -lbcrypt
 	EXTRACXXFLAGS := -lstdc++
-	# So this is a bit hacky: we can't use the DLL version of libstdc++ because
-	# it pulls in the DLL version of libgcc, which means that we end up with 2
-	# instances of the DW2 unwinding implementation. This is a problem on
-	# i686-pc-windows-gnu because each module (DLL/EXE) needs to register its
-	# unwind information with the unwinding implementation, and libstdc++'s
-	# __cxa_throw won't see the unwinding info we registered with our statically
-	# linked libgcc.
-	#
-	# Now, simply statically linking libstdc++ would fix this problem, except
-	# that it is compiled with the expectation that pthreads is dynamically
-	# linked as a DLL and will fail to link with a statically linked libpthread.
-	#
-	# So we end up with the following hack: we link use static:-bundle to only
-	# link the parts of libstdc++ that we actually use, which doesn't include
-	# the dependency on the pthreads DLL.
-	EXTRARSCXXFLAGS := -l static:-bundle=stdc++ -Z unstable-options
 endif
 else
 ifeq ($(UNAME),Darwin)
 	EXTRACFLAGS := -lresolv
 	EXTRACXXFLAGS := -lc++
-	EXTRARSCXXFLAGS := -lc++
 else
 ifeq ($(UNAME),FreeBSD)
 	EXTRACFLAGS := -lm -lpthread -lgcc_s
@@ -140,7 +123,6 @@ ifeq ($(UNAME),OpenBSD)
 else
 	EXTRACFLAGS := -lm -lrt -ldl -lpthread
 	EXTRACXXFLAGS := -lstdc++
-	EXTRARSCXXFLAGS := -lstdc++
 endif
 endif
 endif

src/test/run-make-fulldeps/windows-binary-no-external-deps/Makefile

@@ -5,5 +5,5 @@
 PATH=$(SYSTEMROOT)/system32
 
 all:
-	$(RUSTC) hello.rs
+	$(RUSTC) hello.rs -C target-feature=+crt-static
 	$(TMPDIR)/hello.exe

src/test/run-make/issue-36710/Makefile

@@ -14,7 +14,7 @@ all: foo
 	$(call RUN,foo)
 
 foo: foo.rs $(call NATIVE_STATICLIB,foo)
-	$(RUSTC) $< -lfoo $(EXTRARSCXXFLAGS) --target $(TARGET)
+	$(RUSTC) $< -lfoo $(EXTRACXXFLAGS) --target $(TARGET)
 
 $(TMPDIR)/libfoo.o: foo.cpp
 	$(call COMPILE_OBJ_CXX,$@,$<)