Specialize Vec::from_elem<u8> to use calloc or memset

Fixes #38723.

1 files changed, 16 insertions, 1 deletions

diff --git a/src/liballoc/raw_vec.rs b/src/liballoc/raw_vec.rs
index 357a2724e00..6a53d3a9ca5 100644
--- a/src/liballoc/raw_vec.rs
+++ b/src/liballoc/raw_vec.rs
@@ -81,7 +81,18 @@ impl<T> RawVec<T> {
     /// # Aborts
     ///
     /// Aborts on OOM
+    #[inline]
     pub fn with_capacity(cap: usize) -> Self {
+        RawVec::allocate(cap, false)
+    }
+
+    /// Like `with_capacity` but guarantees the buffer is zeroed.
+    #[inline]
+    pub fn with_capacity_zeroed(cap: usize) -> Self {
+        RawVec::allocate(cap, true)
+    }
+
+    fn allocate(cap: usize, zeroed: bool) -> Self {
         unsafe {
             let elem_size = mem::size_of::<T>();
 
@@ -93,7 +104,11 @@ impl<T> RawVec<T> {
                 heap::EMPTY as *mut u8
             } else {
                 let align = mem::align_of::<T>();
-                let ptr = heap::allocate(alloc_size, align);
+                let ptr = if zeroed {
+                    heap::allocate_zeroed(alloc_size, align)
+                } else {
+                    heap::allocate(alloc_size, align)
+                };
                 if ptr.is_null() {
                     oom()
                 }