1 files changed, 94 insertions, 0 deletions
diff --git a/library/std/src/sys/alloc/mod.rs b/library/std/src/sys/alloc/mod.rs
new file mode 100644
index 00000000000..2c0b533a570
--- /dev/null
+++ b/library/std/src/sys/alloc/mod.rs
@@ -0,0 +1,94 @@
+#![forbid(unsafe_op_in_unsafe_fn)]
+
+use crate::alloc::{GlobalAlloc, Layout, System};
+use crate::ptr;
+
+// The minimum alignment guaranteed by the architecture. This value is used to
+// add fast paths for low alignment values.
+#[allow(dead_code)]
+const MIN_ALIGN: usize = if cfg!(any(
+    all(target_arch = "riscv32", any(target_os = "espidf", target_os = "zkvm")),
+    all(target_arch = "xtensa", target_os = "espidf"),
+)) {
+    // The allocator on the esp-idf and zkvm platforms guarantees 4 byte alignment.
+    4
+} else if cfg!(any(
+    target_arch = "x86",
+    target_arch = "arm",
+    target_arch = "m68k",
+    target_arch = "csky",
+    target_arch = "mips",
+    target_arch = "mips32r6",
+    target_arch = "powerpc",
+    target_arch = "powerpc64",
+    target_arch = "sparc",
+    target_arch = "wasm32",
+    target_arch = "hexagon",
+    target_arch = "riscv32",
+    target_arch = "xtensa",
+)) {
+    8
+} else if cfg!(any(
+    target_arch = "x86_64",
+    target_arch = "aarch64",
+    target_arch = "arm64ec",
+    target_arch = "loongarch64",
+    target_arch = "mips64",
+    target_arch = "mips64r6",
+    target_arch = "s390x",
+    target_arch = "sparc64",
+    target_arch = "riscv64",
+    target_arch = "wasm64",
+)) {
+    16
+} else {
+    panic!("add a value for MIN_ALIGN")
+};
+
+#[allow(dead_code)]
+unsafe fn realloc_fallback(
+    alloc: &System,
+    ptr: *mut u8,
+    old_layout: Layout,
+    new_size: usize,
+) -> *mut u8 {
+    // SAFETY: Docs for GlobalAlloc::realloc require this to be valid
+    unsafe {
+        let new_layout = Layout::from_size_align_unchecked(new_size, old_layout.align());
+
+        let new_ptr = GlobalAlloc::alloc(alloc, new_layout);
+        if !new_ptr.is_null() {
+            let size = usize::min(old_layout.size(), new_size);
+            ptr::copy_nonoverlapping(ptr, new_ptr, size);
+            GlobalAlloc::dealloc(alloc, ptr, old_layout);
+        }
+
+        new_ptr
+    }
+}
+
+cfg_if::cfg_if! {
+    if #[cfg(any(
+        target_family = "unix",
+        target_os = "wasi",
+        target_os = "teeos",
+    ))] {
+        mod unix;
+    } else if #[cfg(target_os = "windows")] {
+        mod windows;
+    } else if #[cfg(target_os = "hermit")] {
+        mod hermit;
+    } else if #[cfg(all(target_vendor = "fortanix", target_env = "sgx"))] {
+        mod sgx;
+    } else if #[cfg(target_os = "solid_asp3")] {
+        mod solid;
+    } else if #[cfg(target_os = "uefi")] {
+        mod uefi;
+    } else if #[cfg(target_family = "wasm")] {
+        mod wasm;
+    } else if #[cfg(target_os = "xous")] {
+        mod xous;
+    } else if #[cfg(target_os = "zkvm")] {
+        mod zkvm;
+    }
+}