diff --git a/build_sysroot/Cargo.toml b/build_sysroot/Cargo.toml
index 725c0b40d89..3ba06fcb0f6 100644
--- a/build_sysroot/Cargo.toml
+++ b/build_sysroot/Cargo.toml
@@ -7,6 +7,7 @@ version = "0.0.0"
 core = { path = "./sysroot_src/src/libcore" }
 compiler_builtins = "0.1"
 alloc = { path = "./sysroot_src/src/liballoc" }
+std = { path = "./sysroot_src/src/libstd" }
 
 alloc_system = { path = "./alloc_system" }
 
diff --git a/example/mini_core.rs b/example/mini_core.rs
index 0ddd3ade401..66314ab3e5d 100644
--- a/example/mini_core.rs
+++ b/example/mini_core.rs
@@ -338,6 +338,7 @@ pub mod libc {
     #[link(name = "c")]
     extern "C" {
         pub fn puts(s: *const u8);
+        pub fn printf(format: *const i8, ...) -> i32;
         pub fn malloc(size: usize) -> *mut u8;
         pub fn free(ptr: *mut u8);
         pub fn memcpy(dst: *mut u8, src: *const u8, size: usize);
diff --git a/example/mini_core_hello_world.rs b/example/mini_core_hello_world.rs
index 1254d917189..871aebddee9 100644
--- a/example/mini_core_hello_world.rs
+++ b/example/mini_core_hello_world.rs
@@ -121,6 +121,8 @@ fn main() {
     //return;
 
     unsafe {
+        printf("Hello %s\n\0" as *const str as *const i8, "printf\0" as *const str as *const i8);
+
         let hello: &[u8] = b"Hello\0" as &[u8; 6];
         let ptr: *const u8 = hello as *const [u8] as *const u8;
         puts(ptr);
diff --git a/example/std_example.rs b/example/std_example.rs
new file mode 100644
index 00000000000..dceb68bcdf4
--- /dev/null
+++ b/example/std_example.rs
@@ -0,0 +1,9 @@
+use std::io::Write;
+
+fn main() {
+    let _ = ::std::iter::repeat('a' as u8).take(10).collect::<Vec<_>>();
+    let stderr = ::std::io::stderr();
+    let mut stderr = stderr.lock();
+
+    writeln!(stderr, "some {} text", "<unknown>").unwrap();
+}
diff --git a/patches/0011-Workaround-for-libstd-crash.patch b/patches/0011-Workaround-for-libstd-crash.patch
new file mode 100644
index 00000000000..46712718dec
--- /dev/null
+++ b/patches/0011-Workaround-for-libstd-crash.patch
@@ -0,0 +1,25 @@
+From 2bc2ef06e118c6fba0626c0e9bf24fed873405b2 Mon Sep 17 00:00:00 2001
+From: bjorn3 <bjorn3@users.noreply.github.com>
+Date: Sat, 29 Dec 2018 12:37:34 +0100
+Subject: [PATCH] Workaround for libstd crash
+
+I think this is related to the use of TLS inside those functions
+---
+ src/libstd/rt.rs | 2 +-
+ 1 file changed, 1 insertions(+), 1 deletions(-)
+
+diff --git a/src/libstd/rt.rs b/src/libstd/rt.rs
+index 5ddb66b..6a0d0b5 100644
+--- a/src/libstd/rt.rs
++++ b/src/libstd/rt.rs
+@@ -51,7 +51,7 @@ fn lang_start_internal(main: &(dyn Fn() -> i32 + Sync + ::panic::RefUnwindSafe),
+         #[cfg(not(feature = "backtrace"))]
+         let exit_code = panic::catch_unwind(move || main());
+
+-        sys_common::cleanup();
++        //sys_common::cleanup();
+         exit_code.unwrap_or(101) as isize
+     }
+ }
+--
+2.17.2 (Apple Git-113)
diff --git a/src/abi.rs b/src/abi.rs
index 70e94db93ae..aa85349b9b8 100644
--- a/src/abi.rs
+++ b/src/abi.rs
@@ -191,12 +191,13 @@ pub fn ty_fn_sig<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, ty: Ty<'tcx>) -> ty::FnS
 pub fn get_function_name_and_sig<'a, 'tcx>(
     tcx: TyCtxt<'a, 'tcx, 'tcx>,
     inst: Instance<'tcx>,
+    support_vararg: bool
 ) -> (String, Signature) {
     assert!(!inst.substs.needs_infer() && !inst.substs.has_param_types());
     let fn_ty = inst.ty(tcx);
     let fn_sig = ty_fn_sig(tcx, fn_ty);
-    if fn_sig.variadic {
-        unimpl!("Variadic functions are not yet supported");
+    if fn_sig.variadic && !support_vararg {
+        unimpl!("Variadic function definitions are not yet supported");
     }
     let sig = clif_sig_from_fn_sig(tcx, fn_sig);
     (tcx.symbol_name(inst).as_str().to_string(), sig)
@@ -208,7 +209,7 @@ pub fn import_function<'a, 'tcx: 'a>(
     module: &mut Module<impl Backend>,
     inst: Instance<'tcx>,
 ) -> FuncId {
-    let (name, sig) = get_function_name_and_sig(tcx, inst);
+    let (name, sig) = get_function_name_and_sig(tcx, inst, true);
     module
         .declare_function(&name, Linkage::Import, &sig)
         .unwrap()
@@ -659,6 +660,23 @@ pub fn codegen_call_inner<'a, 'tcx: 'a>(
         fx.bcx.ins().call(func_ref, &call_args)
     };
 
+    // FIXME find a cleaner way to support varargs
+    if fn_sig.variadic {
+        if fn_sig.abi != Abi::C {
+            unimpl!("Variadic call for non-C abi {:?}", fn_sig.abi);
+        }
+        let sig_ref = fx.bcx.func.dfg.call_signature(call_inst).unwrap();
+        let abi_params = call_args.into_iter().map(|arg| {
+            let ty = fx.bcx.func.dfg.value_type(arg);
+            if !ty.is_int() {
+                // FIXME set %al to upperbound on float args once floats are supported
+                unimpl!("Non int ty {:?} for variadic call", ty);
+            }
+            AbiParam::new(ty)
+        }).collect::<Vec<AbiParam>>();
+        fx.bcx.func.dfg.signatures[sig_ref].params = abi_params;
+    }
+
     match output_pass_mode {
         PassMode::NoPass => {}
         PassMode::ByVal(_) => {
diff --git a/src/base.rs b/src/base.rs
index 94598c65672..d2f31de71d1 100644
--- a/src/base.rs
+++ b/src/base.rs
@@ -65,7 +65,7 @@ fn trans_fn<'a, 'clif, 'tcx: 'a, B: Backend + 'static>(
     let mir = tcx.instance_mir(instance.def);
 
     // Step 2. Declare function
-    let (name, sig) = get_function_name_and_sig(tcx, instance);
+    let (name, sig) = get_function_name_and_sig(tcx, instance, false);
     let func_id = cx.module
         .declare_function(&name, linkage, &sig)
         .unwrap();
diff --git a/src/main_shim.rs b/src/main_shim.rs
index 446089fc9a1..20d79291296 100644
--- a/src/main_shim.rs
+++ b/src/main_shim.rs
@@ -53,8 +53,7 @@ fn create_entry_fn<'a, 'tcx: 'a>(
 
         let instance = Instance::mono(tcx, rust_main_def_id);
 
-        let (main_name, main_sig) = get_function_name_and_sig(tcx, instance);
-
+        let (main_name, main_sig) = get_function_name_and_sig(tcx, instance, false);
         let main_func_id = m
             .declare_function(&main_name, Linkage::Import, &main_sig)
             .unwrap();
diff --git a/test.sh b/test.sh
index 8cc4b0ff817..8cc5b2d186e 100755
--- a/test.sh
+++ b/test.sh
@@ -24,11 +24,16 @@ echo "[BUILD+RUN] alloc_example"
 $RUSTC --sysroot ./build_sysroot/sysroot example/alloc_example.rs --crate-type bin
 ./target/out/alloc_example
 
+echo "[BUILD+RUN] std_example"
+$RUSTC --sysroot ./build_sysroot/sysroot example/std_example.rs --crate-type bin
+./target/out/std_example
+
 echo "[BUILD] mod_bench"
 $RUSTC --sysroot ./build_sysroot/sysroot example/mod_bench.rs --crate-type bin
 
-echo "[BUILD] sysroot in release mode"
-./build_sysroot/build_sysroot.sh --release
+# FIXME linker gives multiple definitions error on Linux
+#echo "[BUILD] sysroot in release mode"
+#./build_sysroot/build_sysroot.sh --release
 
 COMPILE_MOD_BENCH_INLINE="$RUSTC --sysroot ./build_sysroot/sysroot example/mod_bench.rs --crate-type bin -Zmir-opt-level=3 -O --crate-name mod_bench_inline"
 COMPILE_MOD_BENCH_LLVM_0="rustc example/mod_bench.rs --crate-type bin -Copt-level=0 -o target/out/mod_bench_llvm_0 -Cpanic=abort"