Ignore malformed environment strings like glibc does

Otherwise, the iterator and the functions for getting specific
environment variables might disagree, for environments like

    FOOBAR

Variable names starting with equals sign are OK:

glibc only interprets equals signs not in the first position as
separators between variable name and variable value. Instead of skipping
them entirely, a leading equals sign is interpreted to be part of the
variable name.

1 files changed, 17 insertions, 8 deletions

diff --git a/src/libstd/sys/unix/os.rs b/src/libstd/sys/unix/os.rs
index 3c53db53f85..5bc5567df2f 100644
--- a/src/libstd/sys/unix/os.rs
+++ b/src/libstd/sys/unix/os.rs
@@ -386,24 +386,33 @@ pub fn env() -> Env {
     let _g = ENV_LOCK.lock();
     return unsafe {
         let mut environ = *environ();
-        if environ as usize == 0 {
+        if environ == ptr::null() {
             panic!("os::env() failure getting env string from OS: {}",
                    io::Error::last_os_error());
         }
         let mut result = Vec::new();
         while *environ != ptr::null() {
-            result.push(parse(CStr::from_ptr(*environ).to_bytes()));
+            if let Some(key_value) = parse(CStr::from_ptr(*environ).to_bytes()) {
+                result.push(key_value);
+            }
             environ = environ.offset(1);
         }
         Env { iter: result.into_iter(), _dont_send_or_sync_me: ptr::null_mut() }
     };
 
-    fn parse(input: &[u8]) -> (OsString, OsString) {
-        let mut it = input.splitn(2, |b| *b == b'=');
-        let key = it.next().unwrap().to_vec();
-        let default: &[u8] = &[];
-        let val = it.next().unwrap_or(default).to_vec();
-        (OsStringExt::from_vec(key), OsStringExt::from_vec(val))
+    fn parse(input: &[u8]) -> Option<(OsString, OsString)> {
+        // Strategy (copied from glibc): Variable name and value are separated
+        // by an ASCII equals sign '='. Since a variable name must not be
+        // empty, allow variable names starting with an equals sign. Skip all
+        // malformed lines.
+        if input.is_empty() {
+            return None;
+        }
+        let pos = input[1..].iter().position(|&b| b == b'=').map(|p| p + 1);
+        pos.map(|p| (
+            OsStringExt::from_vec(input[..p].to_vec()),
+            OsStringExt::from_vec(input[p+1..].to_vec()),
+        ))
     }
 }