std::os has a possible infinite loop/OOM crash when running commands that return a lot of text

[huonw]

I don't have a windows set-up, but I believe the following will crash with OOM (it would be nice for someone to verify that it actually does fail):

use std::os;

fn main() {
    os::setenv("test_env", "x".repeat(10000));
    println!("Set ok!");

    let env = os::getenv("test_env"); // will probably crash here
    println!("Got Some? {}", env.is_some());
}

The following patch theoretically fixes it, but causes the try bot to fail:

diff --git a/src/libstd/os.rs b/src/libstd/os.rs
index 719ed62..7f0e585 100644
--- a/src/libstd/os.rs
+++ b/src/libstd/os.rs
@@ -112,7 +112,7 @@ pub mod win32 {
             let mut done = false;
             while !done {
                 let mut buf = vec::from_elem(n as uint, 0u16);
-                let k = f(buf.as_mut_ptr(), TMPBUF_SZ as DWORD);
+                let k = f(buf.as_mut_ptr(), n);
                 if k == (0 as DWORD) {
                     done = true;
                 } else if k == n &&
@@ -1498,6 +1498,14 @@ mod tests {
     }

     #[test]
+    fn test_env_set_get_huge() {
+        let n = make_rand_name();
+        let s = "x".repeat(10000);
+        setenv(n, s);
+        assert_eq!(getenv(n), Some(s));
+    }
+
+    #[test]
     fn test() {
         assert!((!Path::new("test-path").is_absolute()));

Failure:

---- os::tests::test_env_set_get_huge stdout ----
    task 'os::tests::test_env_set_get_huge' failed at 'assertion failed: end <= self.len()', C:\bot\slave\try-win\build\src\libstd\vec.rs:992

---- run::tests::test_inherit_env stdout ----
    task 'run::tests::test_inherit_env' failed at 'assertion failed: k.is_empty() || output.contains(format!("{}={}" , * k , * v))', C:\bot\slave\try-win\build\src\libstd\run.rs:602

(transmute::<pull, issue>(#12365))