Auto merge of #58189 - kennytm:rollup, r=kennytm

Rollup of 23 pull requests

Successful merges:

 - #58001 (proc_macro: make `TokenStream::from_streams` pre-allocate its vector.)
 - #58096 (Transition linkchecker to 2018 edition)
 - #58097 (Transition remote test to Rust 2018)
 - #58106 (libfmt_macros => 2018)
 - #58107 (libgraphviz => 2018)
 - #58108 (Add NVPTX target to a build manifest)
 - #58109 (librustc_privacy => 2018)
 - #58112 (libpanic_abort => 2018)
 - #58113 (Transition build-manifest to 2018 edition)
 - #58114 (Transition tidy and unstable-book-gen to 2018 edition)
 - #58116 (Include the span of attributes of the lhs to the span of the assignment expression)
 - #58117 (Transition rustdoc-theme to 2018 edition)
 - #58128 (libunwind => 2018)
 - #58138 (Fix #58101)
 - #58139 (hir: add more HirId methods)
 - #58141 (Remove weasel word in docs for iter's take_while())
 - #58142 (Remove stray FIXME)
 - #58145 (Add #[must_use] to core::task::Poll)
 - #58162 (Add more debugging code to track down appveyor 259 exit code)
 - #58169 (Update contributor name in .mailmap)
 - #58172 (update split docs)
 - #58182 (SGX target: handle empty user buffers correctly)
 - #58186 (Add Rustlings to the doc index)

Failed merges:

r? @ghost

3 files changed, 8 insertions, 5 deletions

diff --git a/src/libstd/sys/sgx/abi/usercalls/alloc.rs b/src/libstd/sys/sgx/abi/usercalls/alloc.rs
index 8d0013a235a..2efbaa9b148 100644
--- a/src/libstd/sys/sgx/abi/usercalls/alloc.rs
+++ b/src/libstd/sys/sgx/abi/usercalls/alloc.rs
@@ -537,7 +537,12 @@ impl UserRef<super::raw::ByteBuffer> {
     pub fn copy_user_buffer(&self) -> Vec<u8> {
         unsafe {
             let buf = self.to_enclave();
-            User::from_raw_parts(buf.data as _, buf.len).to_enclave()
+            if buf.len > 0 {
+                User::from_raw_parts(buf.data as _, buf.len).to_enclave()
+            } else {
+                // Mustn't look at `data` or call `free` if `len` is `0`.
+                Vec::with_capacity(0)
+            }
         }
     }
 }
diff --git a/src/libstd/sys/sgx/abi/usercalls/mod.rs b/src/libstd/sys/sgx/abi/usercalls/mod.rs
index 4e889c172ef..bae044b906b 100644
--- a/src/libstd/sys/sgx/abi/usercalls/mod.rs
+++ b/src/libstd/sys/sgx/abi/usercalls/mod.rs
@@ -22,7 +22,8 @@ pub fn read(fd: Fd, buf: &mut [u8]) -> IoResult<usize> {
 #[unstable(feature = "sgx_platform", issue = "56975")]
 pub fn read_alloc(fd: Fd) -> IoResult<Vec<u8>> {
     unsafe {
-        let mut userbuf = alloc::User::<ByteBuffer>::uninitialized();
+        let userbuf = ByteBuffer { data: ::ptr::null_mut(), len: 0 };
+        let mut userbuf = alloc::User::new_from_enclave(&userbuf);
         raw::read_alloc(fd, userbuf.as_raw_mut_ptr()).from_sgx_result()?;
         Ok(userbuf.copy_user_buffer())
     }
diff --git a/src/libstd/sys/sgx/rwlock.rs b/src/libstd/sys/sgx/rwlock.rs
index 43ceae7d33b..33163a556c1 100644
--- a/src/libstd/sys/sgx/rwlock.rs
+++ b/src/libstd/sys/sgx/rwlock.rs
@@ -19,9 +19,6 @@ unsafe fn rw_lock_size_assert(r: RWLock) {
     mem::transmute::<RWLock, [u8; 128]>(r);
 }
 
-//unsafe impl Send for RWLock {}
-//unsafe impl Sync for RWLock {} // FIXME
-
 impl RWLock {
     pub const fn new() -> RWLock {
         RWLock {