5 files changed, 64 insertions, 2 deletions
diff --git a/tests/ui/c-variadic/naked.rs b/tests/ui/c-variadic/naked.rs
new file mode 100644
index 00000000000..46b59395485
--- /dev/null
+++ b/tests/ui/c-variadic/naked.rs
@@ -0,0 +1,40 @@
+//@ run-pass
+//@ only-x86_64
+//@ only-linux
+#![feature(c_variadic)]
+
+#[repr(C)]
+#[derive(Debug, PartialEq)]
+struct Data(i32, f64);
+
+#[unsafe(naked)]
+unsafe extern "C" fn c_variadic(_: ...) -> Data {
+    // This assembly was generated with GCC, because clang/LLVM is unable to
+    // optimize out the spilling of all registers to the stack.
+    core::arch::naked_asm!(
+        "        sub     rsp, 96",
+        "        mov     QWORD PTR [rsp-88], rdi",
+        "        test    al, al",
+        "        je      .L7",
+        "        movaps  XMMWORD PTR [rsp-40], xmm0",
+        ".L7:",
+        "        lea     rax, [rsp+104]",
+        "        mov     rcx, QWORD PTR [rsp-40]",
+        "        mov     DWORD PTR [rsp-112], 0",
+        "        mov     QWORD PTR [rsp-104], rax",
+        "        lea     rax, [rsp-88]",
+        "        mov     QWORD PTR [rsp-96], rax",
+        "        movq    xmm0, rcx",
+        "        mov     eax, DWORD PTR [rsp-88]",
+        "        mov     DWORD PTR [rsp-108], 48",
+        "        add     rsp, 96",
+        "        ret",
+    )
+}
+
+fn main() {
+    unsafe {
+        assert_eq!(c_variadic(1, 2.0), Data(1, 2.0));
+        assert_eq!(c_variadic(123, 4.56), Data(123, 4.56));
+    }
+}
diff --git a/tests/ui/explicit-tail-calls/c-variadic.rs b/tests/ui/explicit-tail-calls/c-variadic.rs
new file mode 100644
index 00000000000..e6eebe4228e
--- /dev/null
+++ b/tests/ui/explicit-tail-calls/c-variadic.rs
@@ -0,0 +1,14 @@
+#![expect(incomplete_features)]
+#![feature(c_variadic, explicit_tail_calls)]
+#![allow(unused)]
+
+unsafe extern "C" fn foo(mut ap: ...) -> u32 {
+    ap.arg::<u32>()
+}
+
+extern "C" fn bar() -> u32 {
+    unsafe { become foo(1, 2, 3) }
+    //~^ ERROR c-variadic functions can't be tail-called
+}
+
+fn main() {}
diff --git a/tests/ui/explicit-tail-calls/c-variadic.stderr b/tests/ui/explicit-tail-calls/c-variadic.stderr
new file mode 100644
index 00000000000..5293339d218
--- /dev/null
+++ b/tests/ui/explicit-tail-calls/c-variadic.stderr
@@ -0,0 +1,8 @@
+error: c-variadic functions can't be tail-called
+  --> $DIR/c-variadic.rs:10:14
+   |
+LL |     unsafe { become foo(1, 2, 3) }
+   |              ^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+
diff --git a/tests/ui/linkage-attr/raw-dylib/windows/dlltool-failed.rs b/tests/ui/linkage-attr/raw-dylib/windows/dlltool-failed.rs
index 92cb60bb16d..dac878c1cd9 100644
--- a/tests/ui/linkage-attr/raw-dylib/windows/dlltool-failed.rs
+++ b/tests/ui/linkage-attr/raw-dylib/windows/dlltool-failed.rs
@@ -20,4 +20,4 @@ pub fn lib_main() {
     unsafe { f(42); }
 }
 
-//~? ERROR Dlltool could not create import library with
+//~? ERROR dlltool could not create import library with
diff --git a/tests/ui/linkage-attr/raw-dylib/windows/dlltool-failed.stderr b/tests/ui/linkage-attr/raw-dylib/windows/dlltool-failed.stderr
index 90cca83d1c1..5f3c29c3a21 100644
--- a/tests/ui/linkage-attr/raw-dylib/windows/dlltool-failed.stderr
+++ b/tests/ui/linkage-attr/raw-dylib/windows/dlltool-failed.stderr
@@ -1,4 +1,4 @@
-error: Dlltool could not create import library with $DLLTOOL -d $DEF_FILE -D foo.dll -l $LIB_FILE $TARGET_MACHINE $ASM_FLAGS --no-leading-underscore $TEMP_PREFIX:
+error: dlltool could not create import library with $DLLTOOL -d $DEF_FILE -D foo.dll -l $LIB_FILE $TARGET_MACHINE $ASM_FLAGS --no-leading-underscore $TEMP_PREFIX:
        
        $DLLTOOL: Syntax error in def file $DEF_FILE:1␍