From 059f6272c346654dfce7a68a6bb0c0aeb1ed756a Mon Sep 17 00:00:00 2001
From: "Brian J. Tarricone" <brian@tarricone.org>
Date: Mon, 15 Feb 2021 23:32:16 -0800
Subject: [PATCH 1/9] Teach rust core about Xtensa VaListImpl and add a custom
 lowering of vaarg for xtensa.

LLVM does not include an implementation of the va_arg instruction for
Xtensa. From what I understand, this is a conscious decision and
instead language frontends are encouraged to implement it themselves.
The rationale seems to be that loading values correctly requires
language and ABI-specific knowledge that LLVM lacks.

This is true of most architectures, and rustc already provides
implementation for a number of them. This commit extends the support to
include Xtensa.

See https://lists.llvm.org/pipermail/llvm-dev/2017-August/116337.html
for some discussion on the topic.

Unfortunately there does not seem to be a reference document for the
semantics of the va_list and va_arg on Xtensa. The most reliable source
is the GCC implementation, which this commit tries to follow. Clang also
provides its own compatible implementation.

This was tested for all the types that rustc allows in variadics.

Co-authored-by: Brian Tarricone <brian@tarricone.org>
Co-authored-by: Jonathan Bastien-Filiatrault <joe@x2a.org>
Co-authored-by: Paul Lietar <paul@lietar.net>
---
 compiler/rustc_codegen_llvm/src/va_arg.rs | 113 +++++++++++++++++++++-
 library/core/Cargo.toml                   |   1 +
 library/core/src/ffi/va_list.rs           |  19 ++++
 3 files changed, 131 insertions(+), 2 deletions(-)

diff --git a/compiler/rustc_codegen_llvm/src/va_arg.rs b/compiler/rustc_codegen_llvm/src/va_arg.rs
index e4c3e748cb5df..8baa69cefe1e2 100644
--- a/compiler/rustc_codegen_llvm/src/va_arg.rs
+++ b/compiler/rustc_codegen_llvm/src/va_arg.rs
@@ -10,6 +10,15 @@ use crate::type_::Type;
 use crate::type_of::LayoutLlvmExt;
 use crate::value::Value;
 
+fn round_up_to_alignment<'ll>(
+    bx: &mut Builder<'_, 'll, '_>,
+    mut value: &'ll Value,
+    align: Align,
+) -> &'ll Value {
+    value = bx.add(value, bx.cx().const_i32(align.bytes() as i32 - 1));
+    return bx.and(value, bx.cx().const_i32(-(align.bytes() as i32)));
+}
+
 fn round_pointer_up_to_alignment<'ll>(
     bx: &mut Builder<'_, 'll, '_>,
     addr: &'ll Value,
@@ -17,8 +26,7 @@ fn round_pointer_up_to_alignment<'ll>(
     ptr_ty: &'ll Type,
 ) -> &'ll Value {
     let mut ptr_as_int = bx.ptrtoint(addr, bx.cx().type_isize());
-    ptr_as_int = bx.add(ptr_as_int, bx.cx().const_i32(align.bytes() as i32 - 1));
-    ptr_as_int = bx.and(ptr_as_int, bx.cx().const_i32(-(align.bytes() as i32)));
+    ptr_as_int = round_up_to_alignment(bx, ptr_as_int, align);
     bx.inttoptr(ptr_as_int, ptr_ty)
 }
 
@@ -270,6 +278,106 @@ fn emit_s390x_va_arg<'ll, 'tcx>(
     bx.load(val_type, val_addr, layout.align.abi)
 }
 
+fn emit_xtensa_va_arg<'ll, 'tcx>(
+    bx: &mut Builder<'_, 'll, 'tcx>,
+    list: OperandRef<'tcx, &'ll Value>,
+    target_ty: Ty<'tcx>,
+) -> &'ll Value {
+    // Implementation of va_arg for Xtensa. There doesn't seem to be an authoritative source for
+    // this, other than "what GCC does".
+    //
+    // The va_list type has three fields:
+    // struct __va_list_tag {
+    //   int32_t *va_stk; // Arguments passed on the stack
+    //   int32_t *va_reg; // Arguments passed in registers, saved to memory by the prologue.
+    //   int32_t va_ndx; // Offset into the arguments, in bytes
+    // };
+    //
+    // The first 24 bytes (equivalent to 6 registers) come from va_reg, the rest from va_stk.
+    // Thus if va_ndx is less than 24, the next va_arg *may* read from va_reg,
+    // otherwise it must come from va_stk.
+    //
+    // Primitive arguments are never split between registers and the stack. For example, if loading an 8 byte
+    // primitive value and va_ndx = 20, we instead bump the offset and read everything from va_stk.
+    let va_list_addr = list.immediate();
+    // FIXME: handle multi-field structs that split across regsave/stack?
+    let layout = bx.cx.layout_of(target_ty);
+    let from_stack = bx.append_sibling_block("va_arg.from_stack");
+    let from_regsave = bx.append_sibling_block("va_arg.from_regsave");
+    let end = bx.append_sibling_block("va_arg.end");
+
+    // (*va).va_ndx
+    let va_reg_offset = 4;
+    let va_ndx_offset = va_reg_offset + 4;
+    let offset_ptr =
+        bx.inbounds_gep(bx.type_i8(), va_list_addr, &[bx.cx.const_usize(va_ndx_offset)]);
+
+    let offset = bx.load(bx.type_i32(), offset_ptr, bx.tcx().data_layout.i32_align.abi);
+    let offset = round_up_to_alignment(bx, offset, layout.align.abi);
+
+    let slot_size = layout.size.align_to(Align::from_bytes(4).unwrap()).bytes() as i32;
+
+    // Update the offset in va_list, by adding the slot's size.
+    let offset_next = bx.add(offset, bx.const_i32(slot_size));
+
+    // Figure out where to look for our value. We do that by checking the end of our slot (offset_next).
+    // If that is within the regsave area, then load from there. Otherwise load from the stack area.
+    let regsave_size = bx.const_i32(24);
+    let use_regsave = bx.icmp(IntPredicate::IntULE, offset_next, regsave_size);
+    bx.cond_br(use_regsave, from_regsave, from_stack);
+
+    bx.switch_to_block(from_regsave);
+    // update va_ndx
+    bx.store(offset_next, offset_ptr, bx.tcx().data_layout.pointer_align.abi);
+
+    // (*va).va_reg
+    let regsave_area_ptr =
+        bx.inbounds_gep(bx.type_i8(), va_list_addr, &[bx.cx.const_usize(va_reg_offset)]);
+    let regsave_area =
+        bx.load(bx.type_ptr(), regsave_area_ptr, bx.tcx().data_layout.pointer_align.abi);
+    let regsave_value_ptr = bx.inbounds_gep(bx.type_i8(), regsave_area, &[offset]);
+    bx.br(end);
+
+    bx.switch_to_block(from_stack);
+
+    // The first time we switch from regsave to stack we needs to adjust our offsets a bit.
+    // va_stk is set up such that the first stack argument is always at va_stk + 32.
+    // The corrected offset is written back into the va_list struct.
+
+    // let offset_corrected = cmp::max(offset, 32);
+    let stack_offset_start = bx.const_i32(32);
+    let needs_correction = bx.icmp(IntPredicate::IntULE, offset, stack_offset_start);
+    let offset_corrected = bx.select(needs_correction, stack_offset_start, offset);
+
+    // let offset_next_corrected = offset_corrected + slot_size;
+    // va_ndx = offset_next_corrected;
+    let offset_next_corrected = bx.add(offset_next, bx.const_i32(slot_size));
+    // update va_ndx
+    bx.store(offset_next_corrected, offset_ptr, bx.tcx().data_layout.pointer_align.abi);
+
+    // let stack_value_ptr = unsafe { (*va).va_stk.byte_add(offset_corrected) };
+    let stack_area_ptr = bx.inbounds_gep(bx.type_i8(), va_list_addr, &[bx.cx.const_usize(0)]);
+    let stack_area = bx.load(bx.type_ptr(), stack_area_ptr, bx.tcx().data_layout.pointer_align.abi);
+    let stack_value_ptr = bx.inbounds_gep(bx.type_i8(), stack_area, &[offset_corrected]);
+    bx.br(end);
+
+    bx.switch_to_block(end);
+
+    // On big-endian, for values smaller than the slot size we'd have to align the read to the end
+    // of the slot rather than the start. While the ISA and GCC support big-endian, all the Xtensa
+    // targets supported by rustc are litte-endian so don't worry about it.
+
+    // if from_regsave {
+    //     unsafe { *regsave_value_ptr }
+    // } else {
+    //     unsafe { *stack_value_ptr }
+    // }
+    assert!(bx.tcx().sess.target.endian == Endian::Little);
+    let value_ptr =
+        bx.phi(bx.type_ptr(), &[regsave_value_ptr, stack_value_ptr], &[from_regsave, from_stack]);
+    return bx.load(layout.llvm_type(bx), value_ptr, layout.align.abi);
+}
+
 pub(super) fn emit_va_arg<'ll, 'tcx>(
     bx: &mut Builder<'_, 'll, 'tcx>,
     addr: OperandRef<'tcx, &'ll Value>,
@@ -302,6 +410,7 @@ pub(super) fn emit_va_arg<'ll, 'tcx>(
             let indirect: bool = target_ty_size > 8 || !target_ty_size.is_power_of_two();
             emit_ptr_va_arg(bx, addr, target_ty, indirect, Align::from_bytes(8).unwrap(), false)
         }
+        "xtensa" => emit_xtensa_va_arg(bx, addr, target_ty),
         // For all other architecture/OS combinations fall back to using
         // the LLVM va_arg instruction.
         // https://llvm.org/docs/LangRef.html#va-arg-instruction
diff --git a/library/core/Cargo.toml b/library/core/Cargo.toml
index cace4582b489a..46c55c437cce5 100644
--- a/library/core/Cargo.toml
+++ b/library/core/Cargo.toml
@@ -43,6 +43,7 @@ check-cfg = [
     'cfg(bootstrap)',
     'cfg(no_fp_fmt_parse)',
     'cfg(stdarch_intel_sde)',
+    'cfg(target_arch, values("xtensa"))',
     # core use #[path] imports to portable-simd `core_simd` crate
     # and to stdarch `core_arch` crate which messes-up with Cargo list
     # of declared features, we therefor expect any feature cfg
diff --git a/library/core/src/ffi/va_list.rs b/library/core/src/ffi/va_list.rs
index 3a224e4d8fe5f..f67c592d8d8f7 100644
--- a/library/core/src/ffi/va_list.rs
+++ b/library/core/src/ffi/va_list.rs
@@ -15,6 +15,7 @@ use crate::ops::{Deref, DerefMut};
         not(target_arch = "aarch64"),
         not(target_arch = "powerpc"),
         not(target_arch = "s390x"),
+        not(target_arch = "xtensa"),
         not(target_arch = "x86_64")
     ),
     all(target_arch = "aarch64", target_vendor = "apple"),
@@ -37,6 +38,7 @@ pub struct VaListImpl<'f> {
         not(target_arch = "aarch64"),
         not(target_arch = "powerpc"),
         not(target_arch = "s390x"),
+        not(target_arch = "xtensa"),
         not(target_arch = "x86_64")
     ),
     all(target_arch = "aarch64", target_vendor = "apple"),
@@ -113,6 +115,18 @@ pub struct VaListImpl<'f> {
     _marker: PhantomData<&'f mut &'f c_void>,
 }
 
+/// Xtensa ABI implementation of a `va_list`.
+#[cfg(target_arch = "xtensa")]
+#[repr(C)]
+#[derive(Debug)]
+#[lang = "va_list"]
+pub struct VaListImpl<'f> {
+    stk: *mut i32,
+    reg: *mut i32,
+    ndx: i32,
+    _marker: PhantomData<&'f mut &'f c_void>,
+}
+
 /// A wrapper for a `va_list`
 #[repr(transparent)]
 #[derive(Debug)]
@@ -124,6 +138,7 @@ pub struct VaList<'a, 'f: 'a> {
             not(target_arch = "s390x"),
             not(target_arch = "x86_64")
         ),
+        target_arch = "xtensa",
         all(target_arch = "aarch64", target_vendor = "apple"),
         target_family = "wasm",
         target_os = "uefi",
@@ -138,6 +153,7 @@ pub struct VaList<'a, 'f: 'a> {
             target_arch = "s390x",
             target_arch = "x86_64"
         ),
+        not(target_arch = "xtensa"),
         any(not(target_arch = "aarch64"), not(target_vendor = "apple")),
         not(target_family = "wasm"),
         not(target_os = "uefi"),
@@ -155,6 +171,7 @@ pub struct VaList<'a, 'f: 'a> {
         not(target_arch = "s390x"),
         not(target_arch = "x86_64")
     ),
+    target_arch = "xtensa",
     all(target_arch = "aarch64", target_vendor = "apple"),
     target_family = "wasm",
     target_os = "uefi",
@@ -173,8 +190,10 @@ impl<'f> VaListImpl<'f> {
         target_arch = "aarch64",
         target_arch = "powerpc",
         target_arch = "s390x",
+        target_arch = "xtensa",
         target_arch = "x86_64"
     ),
+    not(target_arch = "xtensa"),
     any(not(target_arch = "aarch64"), not(target_vendor = "apple")),
     not(target_family = "wasm"),
     not(target_os = "uefi"),

From f4217f42967621c53dbeb1ecdd698c1d17e97b7a Mon Sep 17 00:00:00 2001
From: Ralf Jung <post@ralfj.de>
Date: Wed, 4 Dec 2024 08:37:23 +0100
Subject: [PATCH 2/9] clarify simd_relaxed_fma non-determinism

---
 library/core/src/intrinsics/simd.rs | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/library/core/src/intrinsics/simd.rs b/library/core/src/intrinsics/simd.rs
index 0d24b0558c594..f80a60d471c04 100644
--- a/library/core/src/intrinsics/simd.rs
+++ b/library/core/src/intrinsics/simd.rs
@@ -619,7 +619,8 @@ extern "rust-intrinsic" {
     /// set has support for a fused operation, and that the fused operation is more efficient
     /// than the equivalent, separate pair of mul and add instructions. It is unspecified
     /// whether or not a fused operation is selected, and that may depend on optimization
-    /// level and context, for example.
+    /// level and context, for example. It may even be the case that some SIMD lanes get fused
+    /// and others do not.
     ///
     /// `T` must be a vector of floats.
     #[cfg(not(bootstrap))]

From 76f9aa1d7edb579621f0ab50d18665461bc6ae48 Mon Sep 17 00:00:00 2001
From: Taiki Endo <te316e89@gmail.com>
Date: Thu, 5 Dec 2024 04:23:57 +0900
Subject: [PATCH 3/9] Fix "std" support status of some tier 3 targets

---
 .../spec/targets/powerpc64le_unknown_freebsd.rs  |  4 ++--
 .../src/spec/targets/powerpc_unknown_freebsd.rs  |  2 +-
 .../spec/targets/riscv32gc_unknown_linux_gnu.rs  |  2 +-
 .../spec/targets/riscv32gc_unknown_linux_musl.rs |  2 +-
 .../src/spec/targets/riscv64_linux_android.rs    |  2 +-
 .../spec/targets/riscv64gc_unknown_freebsd.rs    |  2 +-
 .../spec/targets/riscv64gc_unknown_fuchsia.rs    |  2 +-
 .../spec/targets/riscv64gc_unknown_linux_musl.rs |  2 +-
 .../src/spec/targets/s390x_unknown_linux_musl.rs |  2 +-
 src/doc/rustc/src/platform-support.md            | 16 ++++++++--------
 10 files changed, 18 insertions(+), 18 deletions(-)

diff --git a/compiler/rustc_target/src/spec/targets/powerpc64le_unknown_freebsd.rs b/compiler/rustc_target/src/spec/targets/powerpc64le_unknown_freebsd.rs
index e194f5f8a36f3..0c1218bd05939 100644
--- a/compiler/rustc_target/src/spec/targets/powerpc64le_unknown_freebsd.rs
+++ b/compiler/rustc_target/src/spec/targets/powerpc64le_unknown_freebsd.rs
@@ -12,8 +12,8 @@ pub(crate) fn target() -> Target {
         metadata: crate::spec::TargetMetadata {
             description: Some("PPC64LE FreeBSD".into()),
             tier: Some(3),
-            host_tools: Some(false),
-            std: Some(false),
+            host_tools: Some(true),
+            std: Some(true),
         },
         pointer_width: 64,
         data_layout: "e-m:e-Fn32-i64:64-n32:64".into(),
diff --git a/compiler/rustc_target/src/spec/targets/powerpc_unknown_freebsd.rs b/compiler/rustc_target/src/spec/targets/powerpc_unknown_freebsd.rs
index 393946980f8b3..b72f8e8acf8db 100644
--- a/compiler/rustc_target/src/spec/targets/powerpc_unknown_freebsd.rs
+++ b/compiler/rustc_target/src/spec/targets/powerpc_unknown_freebsd.rs
@@ -17,7 +17,7 @@ pub(crate) fn target() -> Target {
             description: Some("PowerPC FreeBSD".into()),
             tier: Some(3),
             host_tools: Some(false),
-            std: Some(false),
+            std: None,
         },
         pointer_width: 32,
         data_layout: "E-m:e-p:32:32-Fn32-i64:64-n32".into(),
diff --git a/compiler/rustc_target/src/spec/targets/riscv32gc_unknown_linux_gnu.rs b/compiler/rustc_target/src/spec/targets/riscv32gc_unknown_linux_gnu.rs
index 8b0a140c9ade5..e9c57b99b9279 100644
--- a/compiler/rustc_target/src/spec/targets/riscv32gc_unknown_linux_gnu.rs
+++ b/compiler/rustc_target/src/spec/targets/riscv32gc_unknown_linux_gnu.rs
@@ -9,7 +9,7 @@ pub(crate) fn target() -> Target {
             description: Some("RISC-V Linux (kernel 5.4, glibc 2.33)".into()),
             tier: Some(3),
             host_tools: Some(false),
-            std: Some(false),
+            std: Some(true),
         },
         pointer_width: 32,
         data_layout: "e-m:e-p:32:32-i64:64-n32-S128".into(),
diff --git a/compiler/rustc_target/src/spec/targets/riscv32gc_unknown_linux_musl.rs b/compiler/rustc_target/src/spec/targets/riscv32gc_unknown_linux_musl.rs
index 212de791e499a..db8482110eb67 100644
--- a/compiler/rustc_target/src/spec/targets/riscv32gc_unknown_linux_musl.rs
+++ b/compiler/rustc_target/src/spec/targets/riscv32gc_unknown_linux_musl.rs
@@ -11,7 +11,7 @@ pub(crate) fn target() -> Target {
             ),
             tier: Some(3),
             host_tools: Some(false),
-            std: Some(false),
+            std: None,
         },
         pointer_width: 32,
         data_layout: "e-m:e-p:32:32-i64:64-n32-S128".into(),
diff --git a/compiler/rustc_target/src/spec/targets/riscv64_linux_android.rs b/compiler/rustc_target/src/spec/targets/riscv64_linux_android.rs
index 8b5d4751a5733..38bf4b006eb74 100644
--- a/compiler/rustc_target/src/spec/targets/riscv64_linux_android.rs
+++ b/compiler/rustc_target/src/spec/targets/riscv64_linux_android.rs
@@ -9,7 +9,7 @@ pub(crate) fn target() -> Target {
             description: Some("RISC-V 64-bit Android".into()),
             tier: Some(3),
             host_tools: Some(false),
-            std: Some(false),
+            std: None,
         },
         pointer_width: 64,
         data_layout: "e-m:e-p:64:64-i64:64-i128:128-n32:64-S128".into(),
diff --git a/compiler/rustc_target/src/spec/targets/riscv64gc_unknown_freebsd.rs b/compiler/rustc_target/src/spec/targets/riscv64gc_unknown_freebsd.rs
index d1b0d801fd60b..db56e264e943a 100644
--- a/compiler/rustc_target/src/spec/targets/riscv64gc_unknown_freebsd.rs
+++ b/compiler/rustc_target/src/spec/targets/riscv64gc_unknown_freebsd.rs
@@ -7,7 +7,7 @@ pub(crate) fn target() -> Target {
             description: Some("RISC-V FreeBSD".into()),
             tier: Some(3),
             host_tools: Some(false),
-            std: Some(false),
+            std: None,
         },
         pointer_width: 64,
         data_layout: "e-m:e-p:64:64-i64:64-i128:128-n32:64-S128".into(),
diff --git a/compiler/rustc_target/src/spec/targets/riscv64gc_unknown_fuchsia.rs b/compiler/rustc_target/src/spec/targets/riscv64gc_unknown_fuchsia.rs
index 6de51f9b07e2a..75b7dfcbb0922 100644
--- a/compiler/rustc_target/src/spec/targets/riscv64gc_unknown_fuchsia.rs
+++ b/compiler/rustc_target/src/spec/targets/riscv64gc_unknown_fuchsia.rs
@@ -7,7 +7,7 @@ pub(crate) fn target() -> Target {
             description: Some("RISC-V Fuchsia".into()),
             tier: Some(3),
             host_tools: Some(false),
-            std: Some(false),
+            std: None,
         },
         pointer_width: 64,
         data_layout: "e-m:e-p:64:64-i64:64-i128:128-n32:64-S128".into(),
diff --git a/compiler/rustc_target/src/spec/targets/riscv64gc_unknown_linux_musl.rs b/compiler/rustc_target/src/spec/targets/riscv64gc_unknown_linux_musl.rs
index 2e6fce91d4c75..397c202ec1a57 100644
--- a/compiler/rustc_target/src/spec/targets/riscv64gc_unknown_linux_musl.rs
+++ b/compiler/rustc_target/src/spec/targets/riscv64gc_unknown_linux_musl.rs
@@ -9,7 +9,7 @@ pub(crate) fn target() -> Target {
             description: Some("RISC-V Linux (kernel 4.20, musl 1.2.3)".into()),
             tier: Some(3),
             host_tools: Some(false),
-            std: Some(false),
+            std: Some(true),
         },
         pointer_width: 64,
         data_layout: "e-m:e-p:64:64-i64:64-i128:128-n32:64-S128".into(),
diff --git a/compiler/rustc_target/src/spec/targets/s390x_unknown_linux_musl.rs b/compiler/rustc_target/src/spec/targets/s390x_unknown_linux_musl.rs
index 4bde0fb729c75..7a78004927b10 100644
--- a/compiler/rustc_target/src/spec/targets/s390x_unknown_linux_musl.rs
+++ b/compiler/rustc_target/src/spec/targets/s390x_unknown_linux_musl.rs
@@ -19,7 +19,7 @@ pub(crate) fn target() -> Target {
             description: Some("S390x Linux (kernel 3.2, musl 1.2.3)".into()),
             tier: Some(3),
             host_tools: Some(false),
-            std: Some(false),
+            std: Some(true),
         },
         pointer_width: 64,
         data_layout: "E-m:e-i1:8:16-i8:8:16-i64:64-f128:64-v128:64-a:8:16-n32:64".into(),
diff --git a/src/doc/rustc/src/platform-support.md b/src/doc/rustc/src/platform-support.md
index 243cb3b2fc832..3b82d123276d9 100644
--- a/src/doc/rustc/src/platform-support.md
+++ b/src/doc/rustc/src/platform-support.md
@@ -344,15 +344,15 @@ target | std | host | notes
 [`powerpc-wrs-vxworks-spe`](platform-support/vxworks.md) | ✓ |  |
 [`powerpc-wrs-vxworks`](platform-support/vxworks.md) | ✓ |  |
 `powerpc64-unknown-freebsd` | ✓ | ✓ | PPC64 FreeBSD (ELFv1 and ELFv2)
-`powerpc64le-unknown-freebsd` |   |   | PPC64LE FreeBSD
-`powerpc-unknown-freebsd` |   |   | PowerPC FreeBSD
+`powerpc64le-unknown-freebsd` | ✓ | ✓ | PPC64LE FreeBSD
+`powerpc-unknown-freebsd` | ? |   | PowerPC FreeBSD
 `powerpc64-unknown-linux-musl` | ? |  | 64-bit PowerPC Linux with musl 1.2.3
 [`powerpc64-wrs-vxworks`](platform-support/vxworks.md) | ✓ |  |
 `powerpc64le-unknown-linux-musl` | ? |  | 64-bit PowerPC Linux with musl 1.2.3, Little Endian
 [`powerpc64-unknown-openbsd`](platform-support/openbsd.md) | ✓ | ✓ | OpenBSD/powerpc64
 [`powerpc64-ibm-aix`](platform-support/aix.md) | ? |  | 64-bit AIX (7.2 and newer)
-`riscv32gc-unknown-linux-gnu` |   |   | RISC-V Linux (kernel 5.4, glibc 2.33)
-`riscv32gc-unknown-linux-musl` |   |   | RISC-V Linux (kernel 5.4, musl 1.2.3 + RISCV32 support patches)
+`riscv32gc-unknown-linux-gnu` | ✓ |   | RISC-V Linux (kernel 5.4, glibc 2.33)
+`riscv32gc-unknown-linux-musl` | ? |   | RISC-V Linux (kernel 5.4, musl 1.2.3 + RISCV32 support patches)
 [`riscv32im-risc0-zkvm-elf`](platform-support/riscv32im-risc0-zkvm-elf.md) | ? |  | RISC Zero's zero-knowledge Virtual Machine (RV32IM ISA)
 [`riscv32ima-unknown-none-elf`](platform-support/riscv32-unknown-none-elf.md) | * |  | Bare RISC-V (RV32IMA ISA)
 [`riscv32imac-unknown-xous-elf`](platform-support/riscv32imac-unknown-xous-elf.md) | ? |  | RISC-V Xous (RV32IMAC ISA)
@@ -361,13 +361,13 @@ target | std | host | notes
 [`riscv32imafc-esp-espidf`](platform-support/esp-idf.md) | ✓ |  | RISC-V ESP-IDF
 [`riscv32-wrs-vxworks`](platform-support/vxworks.md) | ✓ |  |
 [`riscv64gc-unknown-hermit`](platform-support/hermit.md) | ✓ |   | RISC-V Hermit
-`riscv64gc-unknown-freebsd` |   |   | RISC-V FreeBSD
-`riscv64gc-unknown-fuchsia` |   |   | RISC-V Fuchsia
+`riscv64gc-unknown-freebsd` | ? |   | RISC-V FreeBSD
+`riscv64gc-unknown-fuchsia` | ? |   | RISC-V Fuchsia
 [`riscv64gc-unknown-netbsd`](platform-support/netbsd.md) | ✓ | ✓ | RISC-V NetBSD
 [`riscv64gc-unknown-openbsd`](platform-support/openbsd.md) | ✓ | ✓ | OpenBSD/riscv64
-[`riscv64-linux-android`](platform-support/android.md) |   |   | RISC-V 64-bit Android
+[`riscv64-linux-android`](platform-support/android.md) | ? |   | RISC-V 64-bit Android
 [`riscv64-wrs-vxworks`](platform-support/vxworks.md) | ✓ |  |
-[`s390x-unknown-linux-musl`](platform-support/s390x-unknown-linux-musl.md) |  |  | S390x Linux (kernel 3.2, musl 1.2.3)
+[`s390x-unknown-linux-musl`](platform-support/s390x-unknown-linux-musl.md) | ✓ |  | S390x Linux (kernel 3.2, musl 1.2.3)
 `sparc-unknown-linux-gnu` | ✓ |  | 32-bit SPARC Linux
 [`sparc-unknown-none-elf`](./platform-support/sparc-unknown-none-elf.md) | * |  | Bare 32-bit SPARC V7+
 [`sparc64-unknown-netbsd`](platform-support/netbsd.md) | ✓ | ✓ | NetBSD/sparc64

From e3638e24215e11a5f2081c470fe76c9651857d63 Mon Sep 17 00:00:00 2001
From: Taiki Endo <te316e89@gmail.com>
Date: Thu, 5 Dec 2024 10:49:36 +0900
Subject: [PATCH 4/9] Mark all Linux/Android/BSD/Fuchsia as supporting "std" in
 target-spec metadata

---
 .../src/spec/targets/armv4t_unknown_linux_gnueabi.rs            | 2 +-
 .../src/spec/targets/armv5te_unknown_linux_uclibceabi.rs        | 2 +-
 .../rustc_target/src/spec/targets/m68k_unknown_linux_gnu.rs     | 2 +-
 .../rustc_target/src/spec/targets/mips64_openwrt_linux_musl.rs  | 2 +-
 .../src/spec/targets/mipsisa32r6_unknown_linux_gnu.rs           | 2 +-
 .../src/spec/targets/mipsisa32r6el_unknown_linux_gnu.rs         | 2 +-
 .../src/spec/targets/mipsisa64r6_unknown_linux_gnuabi64.rs      | 2 +-
 .../src/spec/targets/powerpc64_unknown_linux_musl.rs            | 2 +-
 .../src/spec/targets/powerpc64le_unknown_linux_musl.rs          | 2 +-
 .../rustc_target/src/spec/targets/powerpc_unknown_freebsd.rs    | 2 +-
 .../rustc_target/src/spec/targets/powerpc_unknown_linux_musl.rs | 2 +-
 .../rustc_target/src/spec/targets/powerpc_unknown_openbsd.rs    | 2 +-
 .../src/spec/targets/riscv32gc_unknown_linux_musl.rs            | 2 +-
 compiler/rustc_target/src/spec/targets/riscv64_linux_android.rs | 2 +-
 .../rustc_target/src/spec/targets/riscv64gc_unknown_freebsd.rs  | 2 +-
 .../rustc_target/src/spec/targets/riscv64gc_unknown_fuchsia.rs  | 2 +-
 .../src/spec/targets/thumbv7neon_unknown_linux_musleabihf.rs    | 2 +-
 .../rustc_target/src/spec/targets/x86_64_unknown_linux_none.rs  | 2 +-
 18 files changed, 18 insertions(+), 18 deletions(-)

diff --git a/compiler/rustc_target/src/spec/targets/armv4t_unknown_linux_gnueabi.rs b/compiler/rustc_target/src/spec/targets/armv4t_unknown_linux_gnueabi.rs
index 3a2fb753ba147..7ca2babffe9fc 100644
--- a/compiler/rustc_target/src/spec/targets/armv4t_unknown_linux_gnueabi.rs
+++ b/compiler/rustc_target/src/spec/targets/armv4t_unknown_linux_gnueabi.rs
@@ -7,7 +7,7 @@ pub(crate) fn target() -> Target {
             description: Some("Armv4T Linux".into()),
             tier: Some(3),
             host_tools: Some(false),
-            std: None, // ?
+            std: Some(true),
         },
         pointer_width: 32,
         data_layout: "e-m:e-p:32:32-Fi8-i64:64-v128:64:128-a:0:32-n32-S64".into(),
diff --git a/compiler/rustc_target/src/spec/targets/armv5te_unknown_linux_uclibceabi.rs b/compiler/rustc_target/src/spec/targets/armv5te_unknown_linux_uclibceabi.rs
index e0bc1936e221c..154103c36f79c 100644
--- a/compiler/rustc_target/src/spec/targets/armv5te_unknown_linux_uclibceabi.rs
+++ b/compiler/rustc_target/src/spec/targets/armv5te_unknown_linux_uclibceabi.rs
@@ -7,7 +7,7 @@ pub(crate) fn target() -> Target {
             description: Some("Armv5TE Linux with uClibc".into()),
             tier: Some(3),
             host_tools: Some(false),
-            std: None, // ?
+            std: Some(true),
         },
         pointer_width: 32,
         data_layout: "e-m:e-p:32:32-Fi8-i64:64-v128:64:128-a:0:32-n32-S64".into(),
diff --git a/compiler/rustc_target/src/spec/targets/m68k_unknown_linux_gnu.rs b/compiler/rustc_target/src/spec/targets/m68k_unknown_linux_gnu.rs
index 1515d8fe00abc..47c6d80548359 100644
--- a/compiler/rustc_target/src/spec/targets/m68k_unknown_linux_gnu.rs
+++ b/compiler/rustc_target/src/spec/targets/m68k_unknown_linux_gnu.rs
@@ -12,7 +12,7 @@ pub(crate) fn target() -> Target {
             description: Some("Motorola 680x0 Linux".into()),
             tier: Some(3),
             host_tools: Some(false),
-            std: None, // ?
+            std: Some(true),
         },
         pointer_width: 32,
         data_layout: "E-m:e-p:32:16:32-i8:8:8-i16:16:16-i32:16:32-n8:16:32-a:0:16-S16".into(),
diff --git a/compiler/rustc_target/src/spec/targets/mips64_openwrt_linux_musl.rs b/compiler/rustc_target/src/spec/targets/mips64_openwrt_linux_musl.rs
index b7415bf683de2..cc288e042d987 100644
--- a/compiler/rustc_target/src/spec/targets/mips64_openwrt_linux_musl.rs
+++ b/compiler/rustc_target/src/spec/targets/mips64_openwrt_linux_musl.rs
@@ -17,7 +17,7 @@ pub(crate) fn target() -> Target {
             description: Some("MIPS64 for OpenWrt Linux musl 1.2.3".into()),
             tier: Some(3),
             host_tools: Some(false),
-            std: None, // ?
+            std: Some(true),
         },
         pointer_width: 64,
         data_layout: "E-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128".into(),
diff --git a/compiler/rustc_target/src/spec/targets/mipsisa32r6_unknown_linux_gnu.rs b/compiler/rustc_target/src/spec/targets/mipsisa32r6_unknown_linux_gnu.rs
index 2ff06dc6669bb..3ef0988d23570 100644
--- a/compiler/rustc_target/src/spec/targets/mipsisa32r6_unknown_linux_gnu.rs
+++ b/compiler/rustc_target/src/spec/targets/mipsisa32r6_unknown_linux_gnu.rs
@@ -8,7 +8,7 @@ pub(crate) fn target() -> Target {
             description: Some("32-bit MIPS Release 6 Big Endian".into()),
             tier: Some(3),
             host_tools: Some(false),
-            std: None, // ?
+            std: Some(true),
         },
         pointer_width: 32,
         data_layout: "E-m:m-p:32:32-i8:8:32-i16:16:32-i64:64-n32-S64".into(),
diff --git a/compiler/rustc_target/src/spec/targets/mipsisa32r6el_unknown_linux_gnu.rs b/compiler/rustc_target/src/spec/targets/mipsisa32r6el_unknown_linux_gnu.rs
index 05b246698482a..c75023385c220 100644
--- a/compiler/rustc_target/src/spec/targets/mipsisa32r6el_unknown_linux_gnu.rs
+++ b/compiler/rustc_target/src/spec/targets/mipsisa32r6el_unknown_linux_gnu.rs
@@ -7,7 +7,7 @@ pub(crate) fn target() -> Target {
             description: Some("32-bit MIPS Release 6 Little Endian".into()),
             tier: Some(3),
             host_tools: Some(false),
-            std: None, // ?
+            std: Some(true),
         },
         pointer_width: 32,
         data_layout: "e-m:m-p:32:32-i8:8:32-i16:16:32-i64:64-n32-S64".into(),
diff --git a/compiler/rustc_target/src/spec/targets/mipsisa64r6_unknown_linux_gnuabi64.rs b/compiler/rustc_target/src/spec/targets/mipsisa64r6_unknown_linux_gnuabi64.rs
index c5948b745ff59..d0d0ed1acc3f0 100644
--- a/compiler/rustc_target/src/spec/targets/mipsisa64r6_unknown_linux_gnuabi64.rs
+++ b/compiler/rustc_target/src/spec/targets/mipsisa64r6_unknown_linux_gnuabi64.rs
@@ -8,7 +8,7 @@ pub(crate) fn target() -> Target {
             description: Some("64-bit MIPS Release 6 Big Endian".into()),
             tier: Some(3),
             host_tools: Some(false),
-            std: None, // ?
+            std: Some(true),
         },
         pointer_width: 64,
         data_layout: "E-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128".into(),
diff --git a/compiler/rustc_target/src/spec/targets/powerpc64_unknown_linux_musl.rs b/compiler/rustc_target/src/spec/targets/powerpc64_unknown_linux_musl.rs
index 5da891cc13f6d..62c30aebc518e 100644
--- a/compiler/rustc_target/src/spec/targets/powerpc64_unknown_linux_musl.rs
+++ b/compiler/rustc_target/src/spec/targets/powerpc64_unknown_linux_musl.rs
@@ -14,7 +14,7 @@ pub(crate) fn target() -> Target {
             description: Some("64-bit PowerPC Linux with musl 1.2.3".into()),
             tier: Some(3),
             host_tools: Some(false),
-            std: None, // ?
+            std: Some(true),
         },
         pointer_width: 64,
         data_layout: "E-m:e-Fn32-i64:64-n32:64-S128-v256:256:256-v512:512:512".into(),
diff --git a/compiler/rustc_target/src/spec/targets/powerpc64le_unknown_linux_musl.rs b/compiler/rustc_target/src/spec/targets/powerpc64le_unknown_linux_musl.rs
index e2921aa17fe64..50946ae4ce66d 100644
--- a/compiler/rustc_target/src/spec/targets/powerpc64le_unknown_linux_musl.rs
+++ b/compiler/rustc_target/src/spec/targets/powerpc64le_unknown_linux_musl.rs
@@ -13,7 +13,7 @@ pub(crate) fn target() -> Target {
             description: Some("64-bit PowerPC Linux with musl 1.2.3, Little Endian".into()),
             tier: Some(3),
             host_tools: Some(false),
-            std: None, // ?
+            std: Some(true),
         },
         pointer_width: 64,
         data_layout: "e-m:e-Fn32-i64:64-n32:64-S128-v256:256:256-v512:512:512".into(),
diff --git a/compiler/rustc_target/src/spec/targets/powerpc_unknown_freebsd.rs b/compiler/rustc_target/src/spec/targets/powerpc_unknown_freebsd.rs
index b72f8e8acf8db..9cfc2153ac170 100644
--- a/compiler/rustc_target/src/spec/targets/powerpc_unknown_freebsd.rs
+++ b/compiler/rustc_target/src/spec/targets/powerpc_unknown_freebsd.rs
@@ -17,7 +17,7 @@ pub(crate) fn target() -> Target {
             description: Some("PowerPC FreeBSD".into()),
             tier: Some(3),
             host_tools: Some(false),
-            std: None,
+            std: Some(true),
         },
         pointer_width: 32,
         data_layout: "E-m:e-p:32:32-Fn32-i64:64-n32".into(),
diff --git a/compiler/rustc_target/src/spec/targets/powerpc_unknown_linux_musl.rs b/compiler/rustc_target/src/spec/targets/powerpc_unknown_linux_musl.rs
index 9859e8ced4f46..5372a83e29a22 100644
--- a/compiler/rustc_target/src/spec/targets/powerpc_unknown_linux_musl.rs
+++ b/compiler/rustc_target/src/spec/targets/powerpc_unknown_linux_musl.rs
@@ -13,7 +13,7 @@ pub(crate) fn target() -> Target {
             description: Some("PowerPC Linux with musl 1.2.3".into()),
             tier: Some(3),
             host_tools: Some(false),
-            std: None, // ?
+            std: Some(true),
         },
         pointer_width: 32,
         data_layout: "E-m:e-p:32:32-Fn32-i64:64-n32".into(),
diff --git a/compiler/rustc_target/src/spec/targets/powerpc_unknown_openbsd.rs b/compiler/rustc_target/src/spec/targets/powerpc_unknown_openbsd.rs
index a8254af9736c0..7aedc2d0665cb 100644
--- a/compiler/rustc_target/src/spec/targets/powerpc_unknown_openbsd.rs
+++ b/compiler/rustc_target/src/spec/targets/powerpc_unknown_openbsd.rs
@@ -13,7 +13,7 @@ pub(crate) fn target() -> Target {
             description: None,
             tier: Some(3),
             host_tools: Some(false),
-            std: None, // ?
+            std: Some(true),
         },
         pointer_width: 32,
         data_layout: "E-m:e-p:32:32-Fn32-i64:64-n32".into(),
diff --git a/compiler/rustc_target/src/spec/targets/riscv32gc_unknown_linux_musl.rs b/compiler/rustc_target/src/spec/targets/riscv32gc_unknown_linux_musl.rs
index db8482110eb67..08871d9d72bfb 100644
--- a/compiler/rustc_target/src/spec/targets/riscv32gc_unknown_linux_musl.rs
+++ b/compiler/rustc_target/src/spec/targets/riscv32gc_unknown_linux_musl.rs
@@ -11,7 +11,7 @@ pub(crate) fn target() -> Target {
             ),
             tier: Some(3),
             host_tools: Some(false),
-            std: None,
+            std: Some(true),
         },
         pointer_width: 32,
         data_layout: "e-m:e-p:32:32-i64:64-n32-S128".into(),
diff --git a/compiler/rustc_target/src/spec/targets/riscv64_linux_android.rs b/compiler/rustc_target/src/spec/targets/riscv64_linux_android.rs
index 38bf4b006eb74..f694a1cb60dd2 100644
--- a/compiler/rustc_target/src/spec/targets/riscv64_linux_android.rs
+++ b/compiler/rustc_target/src/spec/targets/riscv64_linux_android.rs
@@ -9,7 +9,7 @@ pub(crate) fn target() -> Target {
             description: Some("RISC-V 64-bit Android".into()),
             tier: Some(3),
             host_tools: Some(false),
-            std: None,
+            std: Some(true),
         },
         pointer_width: 64,
         data_layout: "e-m:e-p:64:64-i64:64-i128:128-n32:64-S128".into(),
diff --git a/compiler/rustc_target/src/spec/targets/riscv64gc_unknown_freebsd.rs b/compiler/rustc_target/src/spec/targets/riscv64gc_unknown_freebsd.rs
index db56e264e943a..905bed76db4d0 100644
--- a/compiler/rustc_target/src/spec/targets/riscv64gc_unknown_freebsd.rs
+++ b/compiler/rustc_target/src/spec/targets/riscv64gc_unknown_freebsd.rs
@@ -7,7 +7,7 @@ pub(crate) fn target() -> Target {
             description: Some("RISC-V FreeBSD".into()),
             tier: Some(3),
             host_tools: Some(false),
-            std: None,
+            std: Some(true),
         },
         pointer_width: 64,
         data_layout: "e-m:e-p:64:64-i64:64-i128:128-n32:64-S128".into(),
diff --git a/compiler/rustc_target/src/spec/targets/riscv64gc_unknown_fuchsia.rs b/compiler/rustc_target/src/spec/targets/riscv64gc_unknown_fuchsia.rs
index 75b7dfcbb0922..7a887b604c507 100644
--- a/compiler/rustc_target/src/spec/targets/riscv64gc_unknown_fuchsia.rs
+++ b/compiler/rustc_target/src/spec/targets/riscv64gc_unknown_fuchsia.rs
@@ -7,7 +7,7 @@ pub(crate) fn target() -> Target {
             description: Some("RISC-V Fuchsia".into()),
             tier: Some(3),
             host_tools: Some(false),
-            std: None,
+            std: Some(true),
         },
         pointer_width: 64,
         data_layout: "e-m:e-p:64:64-i64:64-i128:128-n32:64-S128".into(),
diff --git a/compiler/rustc_target/src/spec/targets/thumbv7neon_unknown_linux_musleabihf.rs b/compiler/rustc_target/src/spec/targets/thumbv7neon_unknown_linux_musleabihf.rs
index 5c43ca69bd852..2f539f4f6004d 100644
--- a/compiler/rustc_target/src/spec/targets/thumbv7neon_unknown_linux_musleabihf.rs
+++ b/compiler/rustc_target/src/spec/targets/thumbv7neon_unknown_linux_musleabihf.rs
@@ -16,7 +16,7 @@ pub(crate) fn target() -> Target {
             description: Some("Thumb2-mode ARMv7-A Linux with NEON, musl 1.2.3".into()),
             tier: Some(3),
             host_tools: Some(false),
-            std: None, // ?
+            std: Some(true),
         },
         pointer_width: 32,
         data_layout: "e-m:e-p:32:32-Fi8-i64:64-v128:64:128-a:0:32-n32-S64".into(),
diff --git a/compiler/rustc_target/src/spec/targets/x86_64_unknown_linux_none.rs b/compiler/rustc_target/src/spec/targets/x86_64_unknown_linux_none.rs
index 91eb7b53fea8a..900dbed205c8e 100644
--- a/compiler/rustc_target/src/spec/targets/x86_64_unknown_linux_none.rs
+++ b/compiler/rustc_target/src/spec/targets/x86_64_unknown_linux_none.rs
@@ -14,7 +14,7 @@ pub(crate) fn target() -> Target {
             description: None,
             tier: None,
             host_tools: None,
-            std: None,
+            std: Some(true),
         },
         pointer_width: 64,
         data_layout:

From 736c61e773fcc4ebb566d59d6c879104b8f9eb16 Mon Sep 17 00:00:00 2001
From: jyn <github@jyn.dev>
Date: Wed, 4 Dec 2024 20:54:37 -0500
Subject: [PATCH 5/9] Improve comments for the default backtrace printer

The existing comments were misleading, confusing, and wrong.

Take this comment for example:
```
// Any frames between `__rust_begin_short_backtrace` and `__rust_end_short_backtrace`
// are omitted from the backtrace in short mode, `__rust_end_short_backtrace` will be
// called before the panic hook, so we won't ignore any frames if there is no
// invoke of `__rust_begin_short_backtrace`.
```

this is just wrong. here is an example (full) backtrace:

```
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.01s
     Running `/home/jyn/.local/lib/cargo/target/debug/example`
called `Option::unwrap()` on a `None` value
stack backtrace:
   0:     0x56499698c595 - std::backtrace_rs::backtrace::libunwind::trace::h5ef2cc16e9a7415a
   1:     0x56499698c595 - std::backtrace_rs::backtrace::trace_unsynchronized::h9b5e016e9075f714
   2:     0x56499698c595 - std::sys_common::backtrace::_print_fmt::h2f62c7f9ff224e93
   3:     0x56499698c595 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::hbe51682735731910
   4:     0x5649969aa26b - core::fmt::rt::Argument::fmt::h1994ab2b310d665e
   5:     0x5649969aa26b - core::fmt::write::hade58a36d63468d7
   6:     0x56499698a43f - std::io::Write::write_fmt::h16145587d801a9ab
   7:     0x56499698c36e - std::sys_common::backtrace::_print::ha8082e56201dadb4
   8:     0x56499698c36e - std::sys_common::backtrace::print::he30f96b4e7f6cbfd
   9:     0x56499698d709 - std::panicking::default_hook::{{closure}}::hf0801f6b18a968d3
  10:     0x56499698d4ac - std::panicking::default_hook::hd2defec7eda5aeb0
  11:     0x56499698dc31 - std::panicking::rust_panic_with_hook::hde93283600065c53
  12:     0x56499698daf3 - std::panicking::begin_panic_handler::{{closure}}::h5e151adbdb7ec0c1
  13:     0x56499698ca59 - std::sys_common::backtrace::__rust_end_short_backtrace::he36a1407e0f77700
  14:     0x56499698d7d4 - rust_begin_unwind
  15:     0x5649969a9503 - core::panicking::panic_fmt::h2380d41365f95412
  16:     0x5649969a958c - core::panicking::panic::h38cf8db80e8c6e67
  17:     0x5649969a93e9 - core::option::unwrap_failed::he72696e53ff29a05
  18:     0x5649969722b6 - core::option::Option<T>::unwrap::hb574dc0dc1703062
  19:     0x5649969722b6 - example::main::h7a867aafacd93d75
  20:     0x5649969721db - core::ops::function::FnOnce::call_once::h734f99a5e57291b7
  21:     0x56499697226e - std::sys_common::backtrace::__rust_begin_short_backtrace::h02f5d58c351c4756
  22:     0x564996972241 - std::rt::lang_start::{{closure}}::h8b134fe2c31a4355
  23:     0x564996988662 - core::ops::function::impls::<impl core::ops::function::FnOnce<A> for &F>::call_once::h88d7bb571ee2aaf4
  24:     0x564996988662 - std::panicking::try::do_call::hfb78dfb6599c871d
  25:     0x564996988662 - std::panicking::try::habd041c8c4c8e50c
  27:     0x564996988662 - std::rt::lang_start_internal::{{closure}}::h227591a6f9c0879e
  28:     0x564996988662 - std::panicking::try::do_call::h3c5878333c38916a
  29:     0x564996988662 - std::panicking::try::h5af7b3a127cdae70
  31:     0x564996988662 - std::rt::lang_start_internal::hbc85e809eeace0dd
  32:     0x56499697221a - std::rt::lang_start::ha1eb16922c9cb224
  33:     0x5649969722ee - main
  34:     0x7f031962a1ca - __libc_start_call_main
  35:     0x7f031962a28b - __libc_start_main_impl
  36:     0x5649969720a5 - _start
  37:                0x0 - <unknown>
```

note particularly frames 13-21, from start_backtrace to end_backtrace. with PrintFmt::Short, these are the *only* frames that are printed; i.e. we are doing the exact opposite of the comment.
---
 library/std/src/sys/backtrace.rs | 26 ++++++++++++--------------
 1 file changed, 12 insertions(+), 14 deletions(-)

diff --git a/library/std/src/sys/backtrace.rs b/library/std/src/sys/backtrace.rs
index 4d939e175cf2e..efa6a896dad8f 100644
--- a/library/std/src/sys/backtrace.rs
+++ b/library/std/src/sys/backtrace.rs
@@ -58,8 +58,8 @@ unsafe fn _print_fmt(fmt: &mut fmt::Formatter<'_>, print_fmt: PrintFmt) -> fmt::
     let mut res = Ok(());
     let mut omitted_count: usize = 0;
     let mut first_omit = true;
-    // Start immediately if we're not using a short backtrace.
-    let mut start = print_fmt != PrintFmt::Short;
+    // If we're using a short backtrace, ignore all frames until we're told to start printing.
+    let mut print = print_fmt != PrintFmt::Short;
     set_image_base();
     // SAFETY: we roll our own locking in this town
     unsafe {
@@ -72,27 +72,25 @@ unsafe fn _print_fmt(fmt: &mut fmt::Formatter<'_>, print_fmt: PrintFmt) -> fmt::
             backtrace_rs::resolve_frame_unsynchronized(frame, |symbol| {
                 hit = true;
 
-                // Any frames between `__rust_begin_short_backtrace` and `__rust_end_short_backtrace`
-                // are omitted from the backtrace in short mode, `__rust_end_short_backtrace` will be
-                // called before the panic hook, so we won't ignore any frames if there is no
-                // invoke of `__rust_begin_short_backtrace`.
+                // `__rust_end_short_backtrace` means we are done hiding symbols
+                // for now. Print until we see `__rust_begin_short_backtrace`.
                 if print_fmt == PrintFmt::Short {
                     if let Some(sym) = symbol.name().and_then(|s| s.as_str()) {
-                        if start && sym.contains("__rust_begin_short_backtrace") {
-                            start = false;
+                        if sym.contains("__rust_end_short_backtrace") {
+                            print = true;
                             return;
                         }
-                        if sym.contains("__rust_end_short_backtrace") {
-                            start = true;
+                        if print && sym.contains("__rust_begin_short_backtrace") {
+                            print = false;
                             return;
                         }
-                        if !start {
+                        if !print {
                             omitted_count += 1;
                         }
                     }
                 }
 
-                if start {
+                if print {
                     if omitted_count > 0 {
                         debug_assert!(print_fmt == PrintFmt::Short);
                         // only print the message between the middle of frames
@@ -112,7 +110,7 @@ unsafe fn _print_fmt(fmt: &mut fmt::Formatter<'_>, print_fmt: PrintFmt) -> fmt::
             });
             #[cfg(target_os = "nto")]
             if libc::__my_thread_exit as *mut libc::c_void == frame.ip() {
-                if !hit && start {
+                if !hit && print {
                     use crate::backtrace_rs::SymbolName;
                     res = bt_fmt.frame().print_raw(
                         frame.ip(),
@@ -123,7 +121,7 @@ unsafe fn _print_fmt(fmt: &mut fmt::Formatter<'_>, print_fmt: PrintFmt) -> fmt::
                 }
                 return false;
             }
-            if !hit && start {
+            if !hit && print {
                 res = bt_fmt.frame().print_raw(frame.ip(), None, None, None);
             }
 

From 01442e70a775556a62d7f3678b3c558400094861 Mon Sep 17 00:00:00 2001
From: Chris Denton <chris@chrisdenton.dev>
Date: Thu, 5 Dec 2024 03:13:47 +0000
Subject: [PATCH 6/9] Never close a job after the process is assigned

---
 src/bootstrap/src/utils/job.rs | 22 +++++++++-------------
 1 file changed, 9 insertions(+), 13 deletions(-)

diff --git a/src/bootstrap/src/utils/job.rs b/src/bootstrap/src/utils/job.rs
index c5e892450c4c5..b8c97f3d22308 100644
--- a/src/bootstrap/src/utils/job.rs
+++ b/src/bootstrap/src/utils/job.rs
@@ -124,14 +124,19 @@ mod for_windows {
                 // (only when wrongly setting the environmental variable),
                 // it might be better to improve the experience of the second case
                 // when users have interrupted the parent process and we haven't finish
-                // duplicating the handle yet. We just need close the job object if that occurs.
-                CloseHandle(job).ok();
+                // duplicating the handle yet.
                 return;
             }
         };
 
         let mut parent_handle = HANDLE::default();
-        let r = DuplicateHandle(
+        // If this fails, well at least we tried! An example of DuplicateHandle
+        // failing in the past has been when the wrong python2 package spawned this
+        // build system (e.g., the `python2` package in MSYS instead of
+        // `mingw-w64-x86_64-python2`). Not sure why it failed, but the "failure
+        // mode" here is that we only clean everything up when the build system
+        // dies, not when the python parent does, so not too bad.
+        let _ = DuplicateHandle(
             GetCurrentProcess(),
             job,
             parent,
@@ -140,15 +145,6 @@ mod for_windows {
             false,
             DUPLICATE_SAME_ACCESS,
         );
-
-        // If this failed, well at least we tried! An example of DuplicateHandle
-        // failing in the past has been when the wrong python2 package spawned this
-        // build system (e.g., the `python2` package in MSYS instead of
-        // `mingw-w64-x86_64-python2`). Not sure why it failed, but the "failure
-        // mode" here is that we only clean everything up when the build system
-        // dies, not when the python parent does, so not too bad.
-        if r.is_err() {
-            CloseHandle(job).ok();
-        }
+        CloseHandle(parent).ok();
     }
 }

From a89f340efed5112eda108150ccc47f329aacc0e4 Mon Sep 17 00:00:00 2001
From: Chris Denton <chris@chrisdenton.dev>
Date: Thu, 5 Dec 2024 03:18:53 +0000
Subject: [PATCH 7/9] Nested job objects are now supported in CI

Nested job objects aren't supported on Windows 7 but we've long since moved on from that.
---
 src/bootstrap/src/utils/job.rs | 10 +---------
 1 file changed, 1 insertion(+), 9 deletions(-)

diff --git a/src/bootstrap/src/utils/job.rs b/src/bootstrap/src/utils/job.rs
index b8c97f3d22308..bd2d86498c515 100644
--- a/src/bootstrap/src/utils/job.rs
+++ b/src/bootstrap/src/utils/job.rs
@@ -87,15 +87,7 @@ mod for_windows {
         );
         assert!(r.is_ok(), "{}", io::Error::last_os_error());
 
-        // Assign our process to this job object. Note that if this fails, one very
-        // likely reason is that we are ourselves already in a job object! This can
-        // happen on the build bots that we've got for Windows, or if just anyone
-        // else is instrumenting the build. In this case we just bail out
-        // immediately and assume that they take care of it.
-        //
-        // Also note that nested jobs (why this might fail) are supported in recent
-        // versions of Windows, but the version of Windows that our bots are running
-        // at least don't support nested job objects.
+        // Assign our process to this job object.
         let r = AssignProcessToJobObject(job, GetCurrentProcess());
         if r.is_err() {
             CloseHandle(job).ok();

From 898d75122f9998205516759022b740e873e30dcc Mon Sep 17 00:00:00 2001
From: Chris Denton <chris@chrisdenton.dev>
Date: Thu, 5 Dec 2024 03:45:05 +0000
Subject: [PATCH 8/9] Update comments on Windows job objects

---
 src/bootstrap/bootstrap.py     | 2 ++
 src/bootstrap/src/utils/job.rs | 9 +++++----
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/src/bootstrap/bootstrap.py b/src/bootstrap/bootstrap.py
index 762f4e653e91b..9ef9ccec1937f 100644
--- a/src/bootstrap/bootstrap.py
+++ b/src/bootstrap/bootstrap.py
@@ -1184,6 +1184,8 @@ def bootstrap(args):
     args = [build.bootstrap_binary()]
     args.extend(sys.argv[1:])
     env = os.environ.copy()
+    # The Python process ID is used when creating a Windows job object
+    # (see src\bootstrap\src\utils\job.rs)
     env["BOOTSTRAP_PARENT_ID"] = str(os.getpid())
     env["BOOTSTRAP_PYTHON"] = sys.executable
     run(args, env=env, verbose=build.verbose, is_bootstrap=True)
diff --git a/src/bootstrap/src/utils/job.rs b/src/bootstrap/src/utils/job.rs
index bd2d86498c515..fb69d331d27e1 100644
--- a/src/bootstrap/src/utils/job.rs
+++ b/src/bootstrap/src/utils/job.rs
@@ -15,11 +15,12 @@ pub unsafe fn setup(build: &mut crate::Build) {
 ///
 /// Most of the time when you're running a build system (e.g., make) you expect
 /// Ctrl-C or abnormal termination to actually terminate the entire tree of
-/// process in play, not just the one at the top. This currently works "by
+/// processes in play. This currently works "by
 /// default" on Unix platforms because Ctrl-C actually sends a signal to the
-/// *process group* rather than the parent process, so everything will get torn
-/// down. On Windows, however, this does not happen and Ctrl-C just kills the
-/// parent process.
+/// *process group* so everything will get torn
+/// down. On Windows, however, Ctrl-C is only sent to processes in the same console.
+/// If a process is detached or attached to another console, it won't receive the
+/// signal.
 ///
 /// To achieve the same semantics on Windows we use Job Objects to ensure that
 /// all processes die at the same time. Job objects have a mode of operation

From 34d6a269e9fe57af7b389fdea1a49b5a3654c67e Mon Sep 17 00:00:00 2001
From: onur-ozkan <work@onurozkan.dev>
Date: Thu, 5 Dec 2024 11:17:13 +0300
Subject: [PATCH 9/9] skip `setup::Hook` on non-git sources

Signed-off-by: onur-ozkan <work@onurozkan.dev>
---
 src/bootstrap/src/core/build_steps/setup.rs | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/src/bootstrap/src/core/build_steps/setup.rs b/src/bootstrap/src/core/build_steps/setup.rs
index 3a8f9e48c0da2..7ed01f25c94b2 100644
--- a/src/bootstrap/src/core/build_steps/setup.rs
+++ b/src/bootstrap/src/core/build_steps/setup.rs
@@ -452,24 +452,26 @@ pub struct Hook;
 impl Step for Hook {
     type Output = ();
     const DEFAULT: bool = true;
+
     fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
         run.alias("hook")
     }
+
     fn make_run(run: RunConfig<'_>) {
-        if run.builder.config.dry_run() {
-            return;
-        }
         if let [cmd] = &run.paths[..] {
             if cmd.assert_single_path().path.as_path().as_os_str() == "hook" {
                 run.builder.ensure(Hook);
             }
         }
     }
+
     fn run(self, builder: &Builder<'_>) -> Self::Output {
         let config = &builder.config;
-        if config.dry_run() {
+
+        if config.dry_run() || !config.rust_info.is_managed_git_subrepository() {
             return;
         }
+
         t!(install_git_hook_maybe(builder, config));
     }
 }