Fix rustc panic on second compile_input

src/test/run-make/issue-19371/Makefile

@@ -0,0 +1,9 @@
+-include ../tools.mk
+
+# This test ensures that rustc compile_input can be called twice in one task
+# without causing a panic.
+# The program needs the path to rustc to get sysroot.
+
+all:
+	$(RUSTC) foo.rs
+	$(call RUN,foo $(TMPDIR) $(RUSTC))

src/test/run-make/issue-19371/foo.rs

@@ -0,0 +1,62 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+extern crate rustc;
+extern crate rustc_trans;
+extern crate syntax;
+
+use rustc::session::{build_session, Session};
+use rustc::session::config::{basic_options, build_configuration, OutputTypeExe};
+use rustc_trans::driver::driver::{Input, StrInput, compile_input};
+use syntax::diagnostics::registry::Registry;
+
+fn main() {
+    let src = r#"
+    fn main() {}
+    "#;
+
+    let args = std::os::args();
+
+    if args.len() < 4 {
+        panic!("expected rustc path");
+    }
+
+    let tmpdir = Path::new(args[1].as_slice());
+
+    let mut sysroot = Path::new(args[3].as_slice());
+    sysroot.pop();
+    sysroot.pop();
+
+    compile(src.to_string(), tmpdir.join("out"), sysroot.clone());
+
+    compile(src.to_string(), tmpdir.join("out"), sysroot.clone());
+}
+
+fn basic_sess(sysroot: Path) -> Session {
+    let mut opts = basic_options();
+    opts.output_types = vec![OutputTypeExe];
+    opts.maybe_sysroot = Some(sysroot);
+
+    let descriptions = Registry::new(&rustc::DIAGNOSTICS);
+    let sess = build_session(opts, None, descriptions);
+    sess
+}
+
+fn compile(code: String, output: Path, sysroot: Path) {
+    let sess = basic_sess(sysroot);
+    let cfg = build_configuration(&sess);
+
+    compile_input(sess,
+            cfg,
+            &StrInput(code),
+            &None,
+            &Some(output),
+            None);
+}