Unrolled build for #160440

Rollup merge of #160440 - bjorn3:refactor_unwind4, r=Mark-Simulacrum

Couple of misc improvements to the unwind infrastructure

* Fix `_Unwind_Exception` size on Emscripten.
* Move a link block.
* Remove some manual dummy impls where there is already a dummy fallback.

Follow up to #159785

Author: bors

library/panic_unwind/src/dummy.rs

@@ -4,12 +4,17 @@
 
 use alloc::boxed::Box;
 use core::any::Any;
-use core::intrinsics;
+
+unsafe extern "Rust" {
+    // This is defined in std::rt
+    #[rustc_std_internal_symbol]
+    safe fn __rust_abort() -> !;
+}
 
 pub(crate) unsafe fn cleanup(_ptr: *mut u8) -> Box<dyn Any + Send> {
-    intrinsics::abort()
+    __rust_abort()
 }
 
 pub(crate) unsafe fn panic(_data: Box<dyn Any + Send>) -> u32 {
-    intrinsics::abort()
+    __rust_abort()
 }

library/panic_unwind/src/hermit.rs

@@ -32,10 +32,6 @@ use core::any::Any;
 use core::panic::PanicPayload;
 
 cfg_select! {
-    target_os = "hermit" => {
-        #[path = "hermit.rs"]
-        mod imp;
-    }
     any(
         all(target_family = "windows", target_env = "gnu"),
         target_os = "psp",
@@ -64,6 +60,7 @@ cfg_select! {
         // - os=none ("bare metal" targets)
         // - os=uefi
         // - os=espidf
+        // - os=hermit
         // - nvptx64-nvidia-cuda
         // - arch=avr
         #[path = "dummy.rs"]

library/panic_unwind/src/lib.rs

@@ -14,7 +14,7 @@ mod dwarf;
 
 #[cfg(not(any(test, doctest)))]
 cfg_select! {
-    any(target_env = "msvc", target_family = "wasm", target_os = "motor") => {
+    any(target_env = "msvc", target_family = "wasm") => {
         // 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
@@ -41,6 +41,7 @@ cfg_select! {
         // - os=uefi
         // - os=espidf
         // - os=hermit
+        // - os=motor
         // - nvptx64-nvidia-cuda
         // - arch=avr
     }

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

@@ -48,6 +48,7 @@ cfg_select! {
         // no unwinder on the system!
         // - os=none ("bare metal" targets)
         // - os=hermit
+        // - os=motor
         // - os=uefi
         // - os=cuda
         // - nvptx64-nvidia-cuda
@@ -215,6 +216,10 @@ cfg_select! {
 #[link(name = "gcc_s")]
 unsafe extern "C" {}
 
+#[cfg(all(target_os = "wasi", panic = "unwind"))]
+#[link(name = "unwind")]
+unsafe extern "C" {}
+
 #[cfg(all(target_os = "windows", target_env = "gnu", target_abi = "llvm"))]
 #[link(name = "unwind", kind = "static", modifiers = "-bundle", cfg(target_feature = "crt-static"))]
 #[link(name = "unwind", cfg(not(target_feature = "crt-static")))]

library/unwind/src/lib.rs

@@ -26,13 +26,6 @@ pub enum _Unwind_Context {}
     all(feature = "llvm-libunwind", any(target_os = "fuchsia", target_os = "linux")),
     link(name = "unwind", kind = "static", modifiers = "-bundle")
 )]
-// Explicitly link the `unwind` library on WASI targets.
-//
-// This is provided in the self-contained sysroot for WASI targets by default.
-// Note that Rust defaults to `-Cpanic=abort` on WASI targets meaning that this
-// doesn't end up getting used by default, but this does mean that with
-// `-Zbuild-std` this'll automatically link it in.
-#[cfg_attr(target_os = "wasi", link(name = "unwind"))]
 unsafe extern "C-unwind" {
     pub fn _Unwind_Resume(exception: *mut _Unwind_Exception) -> !;
 }

library/unwind/src/libunwind.rs

@@ -36,7 +36,6 @@ pub const unwinder_private_data_size: usize = cfg_select! {
     target_arch = "s390x" => 2,
     any(target_arch = "sparc", target_arch = "sparc64") => 2,
     any(target_arch = "riscv64", target_arch = "riscv32") => 2,
-    all(target_family = "wasm", target_os = "emscripten") => 20,
     target_family = "wasm" => 2,
     target_arch = "hexagon" => 5,
     any(target_arch = "loongarch32", target_arch = "loongarch64") => 2,