std: Remove the wasm_syscall feature

This commit removes the `wasm_syscall` feature from the
wasm32-unknown-unknown build of the standard library. This feature was
originally intended to allow an opt-in way to interact with the
operating system in a posix-like way but it was never stabilized.
Nowadays with the advent of the `wasm32-wasi` target that should
entirely replace the intentions of the `wasm_syscall` feature.

Author: alexcrichton

config.toml.example

@@ -382,11 +382,6 @@
 # This is the name of the directory in which codegen backends will get installed
 #codegen-backends-dir = "codegen-backends"
 
-# Flag indicating whether `libstd` calls an imported function to handle basic IO
-# when targeting WebAssembly. Enable this to debug tests for the `wasm32-unknown-unknown`
-# target, as without this option the test output will not be captured.
-#wasm-syscall = false
-
 # Indicates whether LLD will be compiled and made available in the sysroot for
 # rustc to execute.
 #lld = false

src/bootstrap/config.rs

@@ -122,7 +122,6 @@ pub struct Config {
 
     // libstd features
     pub backtrace: bool, // support for RUST_BACKTRACE
-    pub wasm_syscall: bool,
 
     // misc
     pub low_priority: bool,
@@ -318,7 +317,6 @@ struct Rust {
     save_toolstates: Option<String>,
     codegen_backends: Option<Vec<String>>,
     codegen_backends_dir: Option<String>,
-    wasm_syscall: Option<bool>,
     lld: Option<bool>,
     lldb: Option<bool>,
     llvm_tools: Option<bool>,
@@ -558,7 +556,6 @@ impl Config {
             if let Some(true) = rust.incremental {
                 config.incremental = true;
             }
-            set(&mut config.wasm_syscall, rust.wasm_syscall);
             set(&mut config.lld_enabled, rust.lld);
             set(&mut config.lldb_enabled, rust.lldb);
             set(&mut config.llvm_tools_enabled, rust.llvm_tools);

src/bootstrap/lib.rs

@@ -498,9 +498,6 @@ impl Build {
         if self.config.profiler {
             features.push_str(" profiler");
         }
-        if self.config.wasm_syscall {
-            features.push_str(" wasm_syscall");
-        }
         features
     }
 

src/bootstrap/test.rs

@@ -1811,16 +1811,6 @@ impl Step for Crate {
                     .expect("nodejs not configured"),
             );
         } else if target.starts_with("wasm32") {
-            // Warn about running tests without the `wasm_syscall` feature enabled.
-            // The javascript shim implements the syscall interface so that test
-            // output can be correctly reported.
-            if !builder.config.wasm_syscall {
-                builder.info(
-                    "Libstd was built without `wasm_syscall` feature enabled: \
-                     test output may not be visible."
-                );
-            }
-
             // On the wasm32-unknown-unknown target we're using LTO which is
             // incompatible with `-C prefer-dynamic`, so disable that here
             cargo.env("RUSTC_NO_PREFER_DYNAMIC", "1");

src/etc/wasm32-shim.js

@@ -15,113 +15,7 @@ const buffer = fs.readFileSync(process.argv[2]);
 Error.stackTraceLimit = 20;
 
 let m = new WebAssembly.Module(buffer);
-
-let memory = null;
-
-function viewstruct(data, fields) {
-  return new Uint32Array(memory.buffer).subarray(data/4, data/4 + fields);
-}
-
-function copystr(a, b) {
-  let view = new Uint8Array(memory.buffer).subarray(a, a + b);
-  return String.fromCharCode.apply(null, view);
-}
-
-function syscall_write([fd, ptr, len]) {
-  let s = copystr(ptr, len);
-  switch (fd) {
-    case 1: process.stdout.write(s); break;
-    case 2: process.stderr.write(s); break;
-  }
-}
-
-function syscall_exit([code]) {
-  process.exit(code);
-}
-
-function syscall_args(params) {
-  let [ptr, len] = params;
-
-  // Calculate total required buffer size
-  let totalLen = -1;
-  for (let i = 2; i < process.argv.length; ++i) {
-    totalLen += Buffer.byteLength(process.argv[i]) + 1;
-  }
-  if (totalLen < 0) { totalLen = 0; }
-  params[2] = totalLen;
-
-  // If buffer is large enough, copy data
-  if (len >= totalLen) {
-    let view = new Uint8Array(memory.buffer);
-    for (let i = 2; i < process.argv.length; ++i) {
-      let value = process.argv[i];
-      Buffer.from(value).copy(view, ptr);
-      ptr += Buffer.byteLength(process.argv[i]) + 1;
-    }
-  }
-}
-
-function syscall_getenv(params) {
-  let [keyPtr, keyLen, valuePtr, valueLen] = params;
-
-  let key = copystr(keyPtr, keyLen);
-  let value = process.env[key];
-
-  if (value == null) {
-    params[4] = 0xFFFFFFFF;
-  } else {
-    let view = new Uint8Array(memory.buffer);
-    let totalLen = Buffer.byteLength(value);
-    params[4] = totalLen;
-    if (valueLen >= totalLen) {
-      Buffer.from(value).copy(view, valuePtr);
-    }
-  }
-}
-
-function syscall_time(params) {
-  let t = Date.now();
-  let secs = Math.floor(t / 1000);
-  let millis = t % 1000;
-  params[1] = Math.floor(secs / 0x100000000);
-  params[2] = secs % 0x100000000;
-  params[3] = Math.floor(millis * 1000000);
-}
-
-let imports = {};
-imports.env = {
-  // These are generated by LLVM itself for various intrinsic calls. Hopefully
-  // one day this is not necessary and something will automatically do this.
-  fmod: function(x, y) { return x % y; },
-  exp2: function(x) { return Math.pow(2, x); },
-  exp2f: function(x) { return Math.pow(2, x); },
-  ldexp: function(x, y) { return x * Math.pow(2, y); },
-  ldexpf: function(x, y) { return x * Math.pow(2, y); },
-  sin: Math.sin,
-  sinf: Math.sin,
-  cos: Math.cos,
-  cosf: Math.cos,
-  log: Math.log,
-  log2: Math.log2,
-  log10: Math.log10,
-  log10f: Math.log10,
-
-  rust_wasm_syscall: function(index, data) {
-    switch (index) {
-      case 1: syscall_write(viewstruct(data, 3)); return true;
-      case 2: syscall_exit(viewstruct(data, 1)); return true;
-      case 3: syscall_args(viewstruct(data, 3)); return true;
-      case 4: syscall_getenv(viewstruct(data, 5)); return true;
-      case 6: syscall_time(viewstruct(data, 4)); return true;
-      default:
-        console.log("Unsupported syscall: " + index);
-        return false;
-    }
-  }
-};
-
-let instance = new WebAssembly.Instance(m, imports);
-memory = instance.exports.memory;
+let instance = new WebAssembly.Instance(m, {});
 try {
   instance.exports.main();
 } catch (e) {

src/libstd/Cargo.toml

@@ -70,11 +70,6 @@ llvm-libunwind = ["unwind/llvm-libunwind"]
 # Make panics and failed asserts immediately abort without formatting any message
 panic_immediate_abort = ["core/panic_immediate_abort"]
 
-# An off-by-default feature which enables a linux-syscall-like ABI for libstd to
-# interoperate with the host environment. Currently not well documented and
-# requires rebuilding the standard library to use it.
-wasm_syscall = []
-
 # Enable std_detect default features for stdarch/crates/std_detect:
 # https://github.com/rust-lang/stdarch/blob/master/crates/std_detect/Cargo.toml
 std_detect_file_io = []

src/libstd/sys/wasm/args.rs

@@ -1,7 +1,6 @@
 use crate::ffi::OsString;
 use crate::marker::PhantomData;
 use crate::vec;
-use crate::sys::ArgsSysCall;
 
 pub unsafe fn init(_argc: isize, _argv: *const *const u8) {
     // On wasm these should always be null, so there's nothing for us to do here
@@ -11,9 +10,8 @@ pub unsafe fn cleanup() {
 }
 
 pub fn args() -> Args {
-    let v = ArgsSysCall::perform();
     Args {
-        iter: v.into_iter(),
+        iter: Vec::new().into_iter(),
         _dont_send_or_sync_me: PhantomData,
     }
 }