1 files changed, 12 insertions, 2 deletions
diff --git a/src/lib/win32_os.rs b/src/lib/win32_os.rs
index 65ee769fb5c..c502ebbfcb7 100644
--- a/src/lib/win32_os.rs
+++ b/src/lib/win32_os.rs
@@ -38,6 +38,7 @@ mod libc_constants {
     fn O_TRUNC() -> int { ret 512; }
     fn O_TEXT() -> int { ret 16384; }
     fn O_BINARY() -> int { ret 32768; }
+    fn O_NOINHERIT() -> int { ret 0x0080; }
     fn S_IRUSR() -> uint {
         ret 256u; // really _S_IREAD  in win32
 
@@ -60,9 +61,18 @@ fn target_os() -> str { ret "win32"; }
 fn dylib_filename(base: str) -> str { ret base + ".dll"; }
 
 fn pipe() -> {in: int, out: int} {
+    // Windows pipes work subtly differently than unix pipes, and their
+    // inheritance has to be handled in a different way that I don't fully
+    // understand. Here we explicitly make the pipe non-inheritable,
+    // which means to pass it to a subprocess they need to be duplicated
+    // first, as in rust_run_program.
     let fds = {mutable in: 0, mutable out: 0};
-    assert (os::libc::_pipe(ptr::addr_of(fds.in), 1024u,
-                            libc_constants::O_BINARY()) == 0);
+    let res = os::libc::_pipe(ptr::addr_of(fds.in), 1024u,
+                            libc_constants::O_BINARY()
+                            | libc_constants::O_NOINHERIT());
+    assert res == 0;
+    assert fds.in != -1 && fds.in != 0;
+    assert fds.out != -1 && fds.in != 0;
     ret {in: fds.in, out: fds.out};
 }