Enable windows-gnu target to link to libgcc dynamically.

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,

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

@@ -84,6 +84,32 @@ 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-nobundle to only
-	# link the parts of libstdc++ that we actually use, which doesn't include
-	# the dependency on the pthreads DLL.
-	EXTRARSCXXFLAGS := -l static-nobundle=stdc++
 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
 	$(call COMPILE_OBJ_CXX,$@,$<)