Allow foreign exceptions to unwind through Rust code

Author: Amanieu

src/doc/unstable-book/src/language-features/lang-items.md

@@ -249,9 +249,8 @@ the source code.
 - Runtime
   - `start`: `libstd/rt.rs`
   - `eh_personality`: `libpanic_unwind/emcc.rs` (EMCC)
-  - `eh_personality`: `libpanic_unwind/seh64_gnu.rs` (SEH64 GNU)
+  - `eh_personality`: `libpanic_unwind/gcc.rs` (GNU)
   - `eh_personality`: `libpanic_unwind/seh.rs` (SEH)
-  - `eh_unwind_resume`: `libpanic_unwind/seh64_gnu.rs` (SEH64 GNU)
   - `eh_unwind_resume`: `libpanic_unwind/gcc.rs` (GCC)
   - `msvc_try_filter`: `libpanic_unwind/seh.rs` (SEH)
   - `panic`: `libcore/panicking.rs`

src/libpanic_unwind/dwarf/eh.rs

@@ -51,7 +51,7 @@ pub enum EHAction {
 
 pub const USING_SJLJ_EXCEPTIONS: bool = cfg!(all(target_os = "ios", target_arch = "arm"));
 
-pub unsafe fn find_eh_action(lsda: *const u8, context: &EHContext<'_>)
+pub unsafe fn find_eh_action(lsda: *const u8, context: &EHContext<'_>, foreign_exception: bool)
     -> Result<EHAction, ()>
 {
     if lsda.is_null() {
@@ -96,7 +96,7 @@ pub unsafe fn find_eh_action(lsda: *const u8, context: &EHContext<'_>)
                     return Ok(EHAction::None)
                 } else {
                     let lpad = lpad_base + cs_lpad;
-                    return Ok(interpret_cs_action(cs_action, lpad))
+                    return Ok(interpret_cs_action(cs_action, lpad, foreign_exception))
                 }
             }
         }
@@ -121,15 +121,17 @@ pub unsafe fn find_eh_action(lsda: *const u8, context: &EHContext<'_>)
                 // Can never have null landing pad for sjlj -- that would have
                 // been indicated by a -1 call site index.
                 let lpad = (cs_lpad + 1) as usize;
-                return Ok(interpret_cs_action(cs_action, lpad))
+                return Ok(interpret_cs_action(cs_action, lpad, foreign_exception))
             }
         }
     }
 }
 
-fn interpret_cs_action(cs_action: u64, lpad: usize) -> EHAction {
+fn interpret_cs_action(cs_action: u64, lpad: usize, foreign_exception: bool) -> EHAction {
     if cs_action == 0 {
         EHAction::Cleanup(lpad)
+    } else if foreign_exception {
+        EHAction::None
     } else {
         EHAction::Catch(lpad)
     }

src/libpanic_unwind/gcc.rs

@@ -133,23 +133,20 @@ const UNWIND_DATA_REG: (i32, i32) = (0, 1); // R0, R1
 // https://github.com/gcc-mirror/gcc/blob/master/libstdc++-v3/libsupc++/eh_personality.cc
 // https://github.com/gcc-mirror/gcc/blob/trunk/libgcc/unwind-c.c
 
-// The personality routine for most of our targets, except ARM, which has a slightly different ABI
-// (however, iOS goes here as it uses SjLj unwinding).  Also, the 64-bit Windows implementation
-// lives in seh64_gnu.rs
-#[cfg(all(any(target_os = "ios", target_os = "netbsd", not(target_arch = "arm"))))]
-#[lang = "eh_personality"]
-#[no_mangle]
+// Shared version of the default personality routine, which is used directly on
+// most targets and indirectly on Windows x86_64 via SEH.
 #[allow(unused)]
-unsafe extern "C" fn rust_eh_personality(version: c_int,
-                                         actions: uw::_Unwind_Action,
-                                         exception_class: uw::_Unwind_Exception_Class,
-                                         exception_object: *mut uw::_Unwind_Exception,
-                                         context: *mut uw::_Unwind_Context)
-                                         -> uw::_Unwind_Reason_Code {
+unsafe extern "C" fn rust_eh_personality_impl(version: c_int,
+                                              actions: uw::_Unwind_Action,
+                                              exception_class: uw::_Unwind_Exception_Class,
+                                              exception_object: *mut uw::_Unwind_Exception,
+                                              context: *mut uw::_Unwind_Context)
+                                              -> uw::_Unwind_Reason_Code {
     if version != 1 {
         return uw::_URC_FATAL_PHASE1_ERROR;
     }
-    let eh_action = match find_eh_action(context) {
+    let foreign_exception = exception_class != rust_exception_class();
+    let eh_action = match find_eh_action(context, foreign_exception) {
         Ok(action) => action,
         Err(_) => return uw::_URC_FATAL_PHASE1_ERROR,
     };
@@ -175,6 +172,23 @@ unsafe extern "C" fn rust_eh_personality(version: c_int,
     }
 }
 
+// The personality routine for most of our targets, except ARM, which has a slightly different ABI
+// (however, iOS goes here as it uses SjLj unwinding).  Also, the 64-bit Windows implementation
+// uses a different personality (below) but eventually also calls rust_eh_personality_impl.
+#[cfg(all(any(target_os = "ios", target_os = "netbsd", not(target_arch = "arm")),
+          not(all(windows, target_arch = "x86_64", target_env = "gnu"))))]
+#[lang = "eh_personality"]
+#[no_mangle]
+#[allow(unused)]
+unsafe extern "C" fn rust_eh_personality(version: c_int,
+                                         actions: uw::_Unwind_Action,
+                                         exception_class: uw::_Unwind_Exception_Class,
+                                         exception_object: *mut uw::_Unwind_Exception,
+                                         context: *mut uw::_Unwind_Context)
+                                         -> uw::_Unwind_Reason_Code {
+    rust_eh_personality_impl(version, actions, exception_class, exception_object, context)
+}
+
 // ARM EHABI personality routine.
 // http://infocenter.arm.com/help/topic/com.arm.doc.ihi0038b/IHI0038B_ehabi.pdf
 #[cfg(all(target_arch = "arm", not(target_os = "ios"), not(target_os = "netbsd")))]
@@ -215,7 +229,9 @@ unsafe extern "C" fn rust_eh_personality(state: uw::_Unwind_State,
     // _Unwind_Context in our libunwind bindings and fetch the required data from there directly,
     // bypassing DWARF compatibility functions.
 
-    let eh_action = match find_eh_action(context) {
+    let exception_class = unsafe { (*exception_object).exception_class };
+    let foreign_exception = exception_class != rust_exception_class();
+    let eh_action = match find_eh_action(context, foreign_exception) {
         Ok(action) => action,
         Err(_) => return uw::_URC_FAILURE,
     };
@@ -259,7 +275,25 @@ unsafe extern "C" fn rust_eh_personality(state: uw::_Unwind_State,
     }
 }
 
-unsafe fn find_eh_action(context: *mut uw::_Unwind_Context)
+// On x86_64 MinGW targets, the unwinding mechanism is SEH however the unwind
+// handler data (aka LSDA) uses GCC-compatible encoding.
+#[cfg(all(windows, target_arch = "x86_64", target_env = "gnu"))]
+#[lang = "eh_personality"]
+#[no_mangle]
+#[allow(nonstandard_style)]
+unsafe extern "C" fn rust_eh_personality(exceptionRecord: *mut uw::EXCEPTION_RECORD,
+                                         establisherFrame: uw::LPVOID,
+                                         contextRecord: *mut uw::CONTEXT,
+                                         dispatcherContext: *mut uw::DISPATCHER_CONTEXT)
+                                         -> uw::EXCEPTION_DISPOSITION {
+    uw::_GCC_specific_handler(exceptionRecord,
+                              establisherFrame,
+                              contextRecord,
+                              dispatcherContext,
+                              rust_eh_personality_impl)
+}
+
+unsafe fn find_eh_action(context: *mut uw::_Unwind_Context, foreign_exception: bool)
     -> Result<EHAction, ()>
 {
     let lsda = uw::_Unwind_GetLanguageSpecificData(context) as *const u8;
@@ -273,11 +307,11 @@ unsafe fn find_eh_action(context: *mut uw::_Unwind_Context)
         get_text_start: &|| uw::_Unwind_GetTextRelBase(context),
         get_data_start: &|| uw::_Unwind_GetDataRelBase(context),
     };
-    eh::find_eh_action(lsda, &eh_context)
+    eh::find_eh_action(lsda, &eh_context, foreign_exception)
 }
 
 // See docs in the `unwind` module.
-#[cfg(all(target_os="windows", target_arch = "x86", target_env="gnu"))]
+#[cfg(all(target_os="windows", any(target_arch = "x86", target_arch = "x86_64"), target_env="gnu"))]
 #[lang = "eh_unwind_resume"]
 #[unwind(allowed)]
 unsafe extern "C" fn rust_eh_unwind_resume(panic_ctx: *mut u8) -> ! {

src/libpanic_unwind/lib.rs

@@ -5,9 +5,8 @@
 //! essentially gets categorized into three buckets currently:
 //!
 //! 1. MSVC targets use SEH in the `seh.rs` file.
-//! 2. The 64-bit MinGW target half-uses SEH and half-use gcc-like information
-//!    in the `seh64_gnu.rs` module.
-//! 3. All other targets use libunwind/libgcc in the `gcc/mod.rs` module.
+//! 2. Emscripten uses C++ exceptions in the `emcc.rs` file.
+//! 3. All other targets use libunwind/libgcc in the `gcc.rs` file.
 //!
 //! More documentation about each implementation can be found in the respective
 //! module.
@@ -52,9 +51,6 @@ cfg_if::cfg_if! {
     } else if #[cfg(target_env = "msvc")] {
         #[path = "seh.rs"]
         mod imp;
-    } else if #[cfg(all(windows, target_arch = "x86_64", target_env = "gnu"))] {
-        #[path = "seh64_gnu.rs"]
-        mod imp;
     } else {
         // Rust runtime's startup objects depend on these symbols, so make them public.
         #[cfg(all(target_os="windows", target_arch = "x86", target_env="gnu"))]

src/libpanic_unwind/seh64_gnu.rs

@@ -244,3 +244,30 @@ if #[cfg(not(all(target_os = "ios", target_arch = "arm")))] {
     }
 }
 } // cfg_if!
+
+cfg_if::cfg_if! {
+if #[cfg(all(windows, target_arch = "x86_64", target_env = "gnu"))] {
+    // We declare these as opaque types. This is fine since you just need to
+    // pass them to _GCC_specific_handler and forget about them.
+    pub enum EXCEPTION_RECORD {}
+    pub type LPVOID = *mut c_void;
+    pub enum CONTEXT {}
+    pub enum DISPATCHER_CONTEXT {}
+    pub type EXCEPTION_DISPOSITION = c_int;
+    type PersonalityFn = unsafe extern "C" fn(version: c_int,
+                                              actions: _Unwind_Action,
+                                              exception_class: _Unwind_Exception_Class,
+                                              exception_object: *mut _Unwind_Exception,
+                                              context: *mut _Unwind_Context)
+                                              -> _Unwind_Reason_Code;
+
+    extern "C" {
+        pub fn _GCC_specific_handler(exceptionRecord: *mut EXCEPTION_RECORD,
+                                establisherFrame: LPVOID,
+                                contextRecord: *mut CONTEXT,
+                                dispatcherContext: *mut DISPATCHER_CONTEXT,
+                                personality: PersonalityFn)
+                                -> EXCEPTION_DISPOSITION;
+    }
+}
+} // cfg_if!

src/libunwind/libunwind.rs

@@ -0,0 +1,10 @@
+-include ../tools.mk
+
+all: foo
+	$(call RUN,foo)
+
+foo: foo.rs $(call NATIVE_STATICLIB,foo)
+	$(RUSTC) $< -lfoo $(EXTRACXXFLAGS)
+
+$(TMPDIR)/libfoo.o: foo.cpp
+	$(call COMPILE_OBJ_CXX,$@,$<)