Auto merge of #50880 - glandium:oom, r=SimonSapin

OOM handling changes

As discussed in https://github.com/rust-lang/rust/issues/49668#issuecomment-384893456 and subsequent.

This does have codegen implications. Even without the hooks, and with a handler that ignores the arguments, the compiler doesn't eliminate calling `rust_oom` with the `Layout`. Even if it managed to eliminate that, with the hooks, I don't know if the compiler would be able to figure out it can skip it if the hook is never set.

A couple implementation notes:
- I went with explicit enums rather than bools because it makes it clearer in callers what is being requested.
- I didn't know what `feature` to put the hook setting functions behind. (and surprisingly, the compile went through without any annotation on the functions)
- There's probably some bikeshedding to do on the naming.

Cc: @Simonsapin, @sfackler

1 files changed, 7 insertions, 6 deletions

diff --git a/src/liballoc/alloc.rs b/src/liballoc/alloc.rs
index 4ae8fc649dd..8753c495737 100644
--- a/src/liballoc/alloc.rs
+++ b/src/liballoc/alloc.rs
@@ -115,7 +115,7 @@ unsafe fn exchange_malloc(size: usize, align: usize) -> *mut u8 {
         if !ptr.is_null() {
             ptr as *mut u8
         } else {
-            oom()
+            oom(layout)
         }
     }
 }
@@ -134,12 +134,13 @@ pub(crate) unsafe fn box_free<T: ?Sized>(ptr: Unique<T>) {
 }
 
 #[rustc_allocator_nounwind]
-pub fn oom() -> ! {
-    extern {
+pub fn oom(layout: Layout) -> ! {
+    #[allow(improper_ctypes)]
+    extern "Rust" {
         #[lang = "oom"]
-        fn oom_impl() -> !;
+        fn oom_impl(layout: Layout) -> !;
     }
-    unsafe { oom_impl() }
+    unsafe { oom_impl(layout) }
 }
 
 #[cfg(test)]
@@ -154,7 +155,7 @@ mod tests {
         unsafe {
             let layout = Layout::from_size_align(1024, 1).unwrap();
             let ptr = Global.alloc_zeroed(layout.clone())
-                .unwrap_or_else(|_| oom());
+                .unwrap_or_else(|_| oom(layout));
 
             let mut i = ptr.cast::<u8>().as_ptr();
             let end = i.offset(layout.size() as isize);