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    #![allow(dead_code)]

    use crate::alloc::{GlobalAlloc, Layout, System};
    use crate::cmp;
    use crate::ptr;

    // The minimum alignment guaranteed by the architecture. This value is used to
    // add fast paths for low alignment values.
    #[cfg(all(any(
        target_arch = "x86",
        target_arch = "arm",
        target_arch = "mips",
        target_arch = "powerpc",
        target_arch = "powerpc64",
        target_arch = "asmjs",
        target_arch = "wasm32",
        target_arch = "hexagon"
    )))]
    pub const MIN_ALIGN: usize = 8;
    #[cfg(all(any(
        target_arch = "x86_64",
        target_arch = "aarch64",
        target_arch = "mips64",
        target_arch = "s390x",
        target_arch = "sparc64",
        target_arch = "riscv64"
    )))]
    pub const MIN_ALIGN: usize = 16;

    pub unsafe fn realloc_fallback(
        alloc: &System,
        ptr: *mut u8,
        old_layout: Layout,
        new_size: usize,
    ) -> *mut u8 {
        // Docs for GlobalAlloc::realloc require this to be valid:
        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 = cmp::min(old_layout.size(), new_size);
            ptr::copy_nonoverlapping(ptr, new_ptr, size);
            GlobalAlloc::dealloc(alloc, ptr, old_layout);
        }
        new_ptr
    }