1 files changed, 22 insertions, 0 deletions
diff --git a/src/test/ui/unknown-llvm-arg.rs b/src/test/ui/unknown-llvm-arg.rs
new file mode 100644
index 000000000..289bae24f
--- /dev/null
+++ b/src/test/ui/unknown-llvm-arg.rs
@@ -0,0 +1,22 @@
+// compile-flags: -Cllvm-args=-not-a-real-llvm-arg
+// normalize-stderr-test "--help" -> "-help"
+// normalize-stderr-test "\n(\n|.)*" -> ""
+
+// I'm seeing "--help" locally, but "-help" in CI, so I'm normalizing it to just "-help".
+
+// Note that the rustc-supplied "program name", given when invoking LLVM, is used by LLVM to
+// generate user-facing error messages and a usage (--help) messages. If the program name is
+// `rustc`, the usage message in response to `--llvm-args="--help"` starts with:
+// ```
+//   USAGE: rustc [options]
+// ```
+// followed by the list of options not to `rustc` but to `llvm`.
+//
+// On the other hand, if the program name is set to `rustc -Cllvm-args="..." with`, the usage
+// message is more clear:
+// ```
+//   USAGE: rustc -Cllvm-args="..." with [options]
+// ```
+// This test captures the effect of the current program name setting on LLVM command line
+// error messages.
+fn main() {}