Support defining C compatible variadic functions

Add support for defining C compatible variadic functions in unsafe rust
with extern "C".

1 files changed, 6 insertions, 0 deletions

diff --git a/src/librustc_codegen_ssa/traits/intrinsic.rs b/src/librustc_codegen_ssa/traits/intrinsic.rs
index 3cd0c39d413..cd527898977 100644
--- a/src/librustc_codegen_ssa/traits/intrinsic.rs
+++ b/src/librustc_codegen_ssa/traits/intrinsic.rs
@@ -20,4 +20,10 @@ pub trait IntrinsicCallMethods<'tcx>: BackendTypes {
     fn abort(&mut self);
     fn assume(&mut self, val: Self::Value);
     fn expect(&mut self, cond: Self::Value, expected: bool) -> Self::Value;
+    /// Trait method used to inject `va_start` on the "spoofed" `VaList` in
+    /// Rust defined C-variadic functions.
+    fn va_start(&mut self, val: Self::Value) -> Self::Value;
+    /// Trait method used to inject `va_end` on the "spoofed" `VaList` before
+    /// Rust defined C-variadic functions return.
+    fn va_end(&mut self, val: Self::Value) -> Self::Value;
 }