Use llvm libunwind for exceptions on wasi

Author: coolreader18

library/panic_unwind/src/lib.rs

@@ -16,10 +16,7 @@
 #![doc(issue_tracker_base_url = "https://github.com/rust-lang/rust/issues/")]
 #![feature(core_intrinsics)]
 #![feature(lang_items)]
-#![cfg_attr(
-    all(target_arch = "wasm32", not(target_os = "emscripten")),
-    feature(link_llvm_intrinsics)
-)]
+#![cfg_attr(all(target_arch = "wasm32", target_os = "unknown"), feature(link_llvm_intrinsics))]
 #![feature(panic_unwind)]
 #![feature(staged_api)]
 #![feature(std_internals)]
@@ -57,6 +54,7 @@ cfg_if::cfg_if! {
         target_os = "solid_asp3",
         all(target_family = "unix", not(target_os = "espidf")),
         all(target_vendor = "fortanix", target_env = "sgx"),
+        target_os = "wasi",
     ))] {
         #[path = "gcc.rs"]
         mod real_imp;

library/std/src/sys/personality/gcc.rs

@@ -87,6 +87,9 @@ const UNWIND_DATA_REG: (i32, i32) = (10, 11); // x10, x11
 #[cfg(target_arch = "loongarch64")]
 const UNWIND_DATA_REG: (i32, i32) = (4, 5); // a0, a1
 
+#[cfg(target_os = "wasi")]
+const UNWIND_DATA_REG: (i32, i32) = (0, 1); // not actually registers
+
 // The following code is based on GCC's C and C++ personality routines.  For reference, see:
 // 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

library/std/src/sys/personality/mod.rs

@@ -16,7 +16,7 @@ mod dwarf;
 cfg_if::cfg_if! {
     if #[cfg(target_os = "emscripten")] {
         mod emcc;
-    } else if #[cfg(any(target_env = "msvc", target_family = "wasm"))] {
+    } else if #[cfg(any(target_env = "msvc", all(target_family = "wasm", target_os = "unknown")))] {
         // This is required by the compiler to exist (e.g., it's a lang item),
         // but it's never actually called by the compiler because
         // __CxxFrameHandler3 (msvc) / __gxx_wasm_personality_v0 (wasm) is the
@@ -33,6 +33,7 @@ cfg_if::cfg_if! {
         target_os = "solid_asp3",
         all(target_family = "unix", not(target_os = "espidf"), not(target_os = "l4re")),
         all(target_vendor = "fortanix", target_env = "sgx"),
+        target_os = "wasi",
     ))] {
         mod gcc;
     } else {

library/unwind/src/lib.rs

@@ -23,6 +23,7 @@ cfg_if::cfg_if! {
         target_os = "psp",
         target_os = "solid_asp3",
         all(target_vendor = "fortanix", target_env = "sgx"),
+        target_os = "wasi",
     ))] {
         mod libunwind;
         pub use libunwind::*;
@@ -31,7 +32,7 @@ cfg_if::cfg_if! {
         pub use unwinding::*;
     } else {
         // no unwinder on the system!
-        // - wasm32 (not emscripten, which is "unix" family)
+        // - wasm32-unknown-unknown
         // - os=none ("bare metal" targets)
         // - os=hermit
         // - os=uefi
@@ -162,3 +163,7 @@ extern "C" {}
 #[cfg(target_os = "hurd")]
 #[link(name = "gcc_s")]
 extern "C" {}
+
+#[cfg(target_os = "wasi")]
+#[link(name = "unwind", kind = "static", modifiers = "-bundle")]
+extern "C" {}

library/unwind/src/libunwind.rs

@@ -81,6 +81,9 @@ pub const unwinder_private_data_size: usize = 35;
 #[cfg(target_arch = "loongarch64")]
 pub const unwinder_private_data_size: usize = 2;
 
+#[cfg(target_family = "wasm")]
+pub const unwinder_private_data_size: usize = 2;
+
 #[repr(C)]
 pub struct _Unwind_Exception {
     pub exception_class: _Unwind_Exception_Class,

src/bootstrap/src/core/build_steps/compile.rs

@@ -341,7 +341,7 @@ fn copy_third_party_objects(
 
     if target == "x86_64-fortanix-unknown-sgx"
         || builder.config.llvm_libunwind(target) == LlvmLibunwind::InTree
-            && (target.contains("linux") || target.contains("fuchsia"))
+            && (target.contains("linux") || target.contains("fuchsia") || target.contains("wasi"))
     {
         let libunwind_path =
             copy_llvm_libunwind(builder, target, &builder.sysroot_libdir(*compiler, target));

src/bootstrap/src/core/build_steps/llvm.rs

@@ -1291,8 +1291,16 @@ impl Step for Libunwind {
                 cfg.define("__NO_MATH_INLINES", None);
                 cfg.define("_LIBUNWIND_IS_BAREMETAL", None);
                 cfg.define("__LIBUNWIND_IS_NATIVE_ONLY", None);
+                cfg.define("_LIBUNWIND_SUPPORT_SEH_UNWIND", None);
                 cfg.define("NDEBUG", None);
             }
+            if self.target.contains("wasi") {
+                cfg.flag("-fdeclspec");
+                cfg.flag("-fwasm-exceptions");
+                cfg.define("_LIBUNWIND_HIDE_SYMBOLS", None);
+                cfg.define("_LIBUNWIND_IS_BAREMETAL", None);
+                cfg.define("__USING_WASM_EXCEPTIONS__", None);
+            }
             if self.target.is_windows() {
                 cfg.define("_LIBUNWIND_HIDE_SYMBOLS", "1");
                 cfg.define("_LIBUNWIND_IS_NATIVE_ONLY", "1");
@@ -1327,13 +1335,17 @@ impl Step for Libunwind {
             }
         }
 
-        let mut c_sources = vec![
-            "Unwind-sjlj.c",
-            "UnwindLevel1-gcc-ext.c",
-            "UnwindLevel1.c",
-            "UnwindRegistersRestore.S",
-            "UnwindRegistersSave.S",
-        ];
+        let mut c_sources = if self.target.contains("wasi") {
+            vec!["Unwind-wasm.c"]
+        } else {
+            vec![
+                "Unwind-sjlj.c",
+                "UnwindLevel1-gcc-ext.c",
+                "UnwindLevel1.c",
+                "UnwindRegistersRestore.S",
+                "UnwindRegistersSave.S",
+            ]
+        };
 
         let cpp_sources = vec!["Unwind-EHABI.cpp", "Unwind-seh.cpp", "libunwind.cpp"];
         let cpp_len = cpp_sources.len();