Add intial support for wasm32-unknown-wasi

ci/docker/wasm32-unknown-wasi/Dockerfile

@@ -0,0 +1,69 @@
+FROM ubuntu:18.04 as reference-sysroot
+
+RUN apt-get update && \
+    apt-get install -y --no-install-recommends \
+    ca-certificates \
+    clang \
+    cmake \
+    curl \
+    g++ \
+    git \
+    libc6-dev \
+    libclang-dev \
+    make \
+    ssh \
+    xz-utils
+
+RUN curl http://releases.llvm.org/8.0.0/clang+llvm-8.0.0-x86_64-linux-gnu-ubuntu-18.04.tar.xz | tar xJf -
+RUN mv /clang+llvm-8.0.0-x86_64-linux-gnu-ubuntu-18.04 /wasmcc
+
+RUN git clone https://github.com/CraneStation/reference-sysroot-wasi && \
+  cd reference-sysroot-wasi && \
+  git reset --hard d5a609fe63926533e1054e539ba5f2693d51bdf5
+RUN make -C reference-sysroot-wasi install -j $(nproc) WASM_CC=/wasmcc/bin/clang INSTALL_DIR=/wasm-sysroot
+COPY docker/wasm32-unknown-wasi/clang.sh /wasm-sysroot/bin/clang
+
+FROM ubuntu:18.04 as wasmtime
+
+RUN apt-get update && \
+    apt-get install -y --no-install-recommends \
+    ca-certificates \
+    clang \
+    cmake \
+    curl \
+    g++ \
+    git \
+    libclang-dev \
+    make \
+    ssh
+
+RUN curl -sSf https://sh.rustup.rs |  sh -s -- -y
+ENV PATH=/root/.cargo/bin:$PATH
+
+RUN apt-get install -y --no-install-recommends python
+RUN git clone https://github.com/CraneStation/wasmtime-wasi wasmtime && \
+  cd wasmtime && \
+  git reset --hard a7ac05df74759a7536b2b1e30adc6ff4867e36c3
+
+# Install wasmtime in /usr/bin, but make sure to remove rust afterwards because
+# we don't want it conflicting with the main Rust we're using to compile
+# `libc`.
+RUN cargo build --release --manifest-path wasmtime/Cargo.toml
+
+FROM ubuntu:18.04
+
+RUN apt-get update && \
+    apt-get install -y --no-install-recommends \
+    gcc \
+    libc6-dev \
+    libxml2
+
+COPY --from=reference-sysroot /wasmcc /wasmcc/
+COPY --from=reference-sysroot /wasm-sysroot/ /wasm-sysroot/
+COPY --from=wasmtime /wasmtime/target/release/wasmtime /usr/bin/
+
+ENV CARGO_TARGET_WASM32_UNKNOWN_WASI_RUNNER=wasmtime \
+  CARGO_TARGET_WASM32_UNKNOWN_WASI_LINKER=/wasm-sysroot/bin/clang \
+  CC_wasm32_unknown_wasi=/wasm-sysroot/bin/clang \
+  PATH=$PATH:/rust/bin \
+  RUSTFLAGS=-Ctarget-feature=-crt-static

ci/docker/wasm32-unknown-wasi/clang.sh

@@ -0,0 +1,2 @@
+#!/bin/sh
+exec /wasmcc/bin/clang --target=wasm32-unknown-wasi --sysroot /wasm-sysroot "$@"

libc-test/build.rs

@@ -5,12 +5,12 @@ extern crate ctest;
 
 use std::env;
 
-#[cfg(unix)]
 fn do_cc() {
-    cc::Build::new().file("src/cmsg.c").compile("cmsg");
+    let target = env::var("TARGET").unwrap();
+    if cfg!(unix) && !target.contains("wasi") {
+        cc::Build::new().file("src/cmsg.c").compile("cmsg");
+    }
 }
-#[cfg(not(unix))]
-fn do_cc() {}
 
 fn do_ctest() {
     let target = env::var("TARGET").unwrap();
@@ -38,6 +38,7 @@ fn do_ctest() {
         t if t.contains("solaris") => return test_solaris(t),
         t if t.contains("netbsd") => return test_netbsd(t),
         t if t.contains("dragonfly") => return test_dragonflybsd(t),
+        t if t.contains("wasi") => return test_wasi(t),
         _ => (),
     }
 
@@ -1866,3 +1867,67 @@ fn test_dragonflybsd(target: &str) {
 
     cfg.generate("../src/lib.rs", "main.rs");
 }
+
+fn test_wasi(target: &str) {
+    assert!(target.contains("wasi"));
+
+    let mut cfg = ctest::TestGenerator::new();
+    cfg.define("_GNU_SOURCE", None);
+
+    headers! { cfg:
+        "errno.h",
+        "fcntl.h",
+        "limits.h",
+        "locale.h",
+        "malloc.h",
+        "stddef.h",
+        "stdint.h",
+        "stdio.h",
+        "stdlib.h",
+        "sys/stat.h",
+        "sys/types.h",
+        "time.h",
+        "unistd.h",
+        "wasi/core.h",
+        "wasi/libc.h",
+        "wchar.h",
+    }
+
+    cfg.type_name(move |ty, is_struct, is_union| match ty {
+        "FILE" => ty.to_string(),
+        t if is_union => format!("union {}", t),
+        t if t.starts_with("__wasi") && t.ends_with("_u") => format!("union {}", t),
+        t if t.starts_with("__wasi") && is_struct => format!("struct {}", t),
+        t if t.ends_with("_t") => t.to_string(),
+        t if is_struct => format!("struct {}", t),
+        t => t.to_string(),
+    });
+
+    // This is an opaque struct but we go through shenanigans to define values
+    // for it
+    cfg.skip_struct(move |ty| ty == "__clockid");
+
+    cfg.field_name(move |_struct, field| {
+        match field {
+			// deal with fields as rust keywords
+            "type_" => "type".to_string(),
+            s => s.to_string(),
+        }
+    });
+
+    cfg.skip_static(move |name| {
+        match name {
+            // wasi shenanigans for defining CLOCK_REALTIME and such
+            s if s.starts_with("__CLOCK") => true,
+            _ => false,
+        }
+    });
+
+    // Looks like LLD doesn't merge duplicate imports, so if the Rust
+    // code imports from a module and the C code also imports from a
+    // module we end up with two imports of function pointers which
+    // improt the same thing bug have different function pointers
+    cfg.skip_fn_ptrcheck(|f| f.starts_with("__wasi"));
+
+    cfg.generate("../src/lib.rs", "main.rs");
+}

src/lib.rs

@@ -112,7 +112,10 @@ cfg_if! {
     } else if #[cfg(all(target_env = "sgx", target_vendor = "fortanix"))] {
         mod sgx;
         pub use sgx::*;
-    }  else {
+    } else if #[cfg(target_env = "wasi")] {
+        mod wasi;
+        pub use wasi::*;
+    } else {
         // non-supported targets: empty...
     }
 }