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,
     }
 }

src/libstd/sys/wasm/mod.rs

@@ -15,11 +15,6 @@
 //! guaranteed to be a runtime error!
 
 use crate::os::raw::c_char;
-use crate::ptr;
-use crate::sys::os_str::Buf;
-use crate::sys_common::{AsInner, FromInner};
-use crate::ffi::{OsString, OsStr};
-use crate::time::Duration;
 
 pub mod alloc;
 pub mod args;
@@ -89,7 +84,7 @@ pub unsafe fn strlen(mut s: *const c_char) -> usize {
 }
 
 pub unsafe fn abort_internal() -> ! {
-    ExitSysCall::perform(1)
+    crate::arch::wasm32::unreachable()
 }
 
 // We don't have randomness yet, but I totally used a random number generator to
@@ -100,218 +95,3 @@ pub unsafe fn abort_internal() -> ! {
 pub fn hashmap_random_keys() -> (u64, u64) {
     (1, 2)
 }
-
-// Implement a minimal set of system calls to enable basic IO
-pub enum SysCallIndex {
-    Read = 0,
-    Write = 1,
-    Exit = 2,
-    Args = 3,
-    GetEnv = 4,
-    SetEnv = 5,
-    Time = 6,
-}
-
-#[repr(C)]
-pub struct ReadSysCall {
-    fd: usize,
-    ptr: *mut u8,
-    len: usize,
-    result: usize,
-}
-
-impl ReadSysCall {
-    pub fn perform(fd: usize, buffer: &mut [u8]) -> usize {
-        let mut call_record = ReadSysCall {
-            fd,
-            len: buffer.len(),
-            ptr: buffer.as_mut_ptr(),
-            result: 0
-        };
-        if unsafe { syscall(SysCallIndex::Read, &mut call_record) } {
-            call_record.result
-        } else {
-            0
-        }
-    }
-}
-
-#[repr(C)]
-pub struct WriteSysCall {
-    fd: usize,
-    ptr: *const u8,
-    len: usize,
-}
-
-impl WriteSysCall {
-    pub fn perform(fd: usize, buffer: &[u8]) {
-        let mut call_record = WriteSysCall {
-            fd,
-            len: buffer.len(),
-            ptr: buffer.as_ptr()
-        };
-        unsafe { syscall(SysCallIndex::Write, &mut call_record); }
-    }
-}
-
-#[repr(C)]
-pub struct ExitSysCall {
-    code: usize,
-}
-
-impl ExitSysCall {
-    pub fn perform(code: usize) -> ! {
-        let mut call_record = ExitSysCall {
-            code
-        };
-        unsafe {
-            syscall(SysCallIndex::Exit, &mut call_record);
-            crate::intrinsics::abort();
-        }
-    }
-}
-
-fn receive_buffer<E, F: FnMut(&mut [u8]) -> Result<usize, E>>(estimate: usize, mut f: F)
-    -> Result<Vec<u8>, E>
-{
-    let mut buffer = vec![0; estimate];
-    loop {
-        let result = f(&mut buffer)?;
-        if result <= buffer.len() {
-            buffer.truncate(result);
-            break;
-        }
-        buffer.resize(result, 0);
-    }
-    Ok(buffer)
-}
-
-#[repr(C)]
-pub struct ArgsSysCall {
-    ptr: *mut u8,
-    len: usize,
-    result: usize
-}
-
-impl ArgsSysCall {
-    pub fn perform() -> Vec<OsString> {
-        receive_buffer(1024, |buffer| -> Result<usize, !> {
-            let mut call_record = ArgsSysCall {
-                len: buffer.len(),
-                ptr: buffer.as_mut_ptr(),
-                result: 0
-            };
-            if unsafe { syscall(SysCallIndex::Args, &mut call_record) } {
-                Ok(call_record.result)
-            } else {
-                Ok(0)
-            }
-        })
-            .unwrap()
-            .split(|b| *b == 0)
-            .map(|s| FromInner::from_inner(Buf { inner: s.to_owned() }))
-            .collect()
-    }
-}
-
-#[repr(C)]
-pub struct GetEnvSysCall {
-    key_ptr: *const u8,
-    key_len: usize,
-    value_ptr: *mut u8,
-    value_len: usize,
-    result: usize
-}
-
-impl GetEnvSysCall {
-    pub fn perform(key: &OsStr) -> Option<OsString> {
-        let key_buf = &AsInner::as_inner(key).inner;
-        receive_buffer(64, |buffer| {
-            let mut call_record = GetEnvSysCall {
-                key_len: key_buf.len(),
-                key_ptr: key_buf.as_ptr(),
-                value_len: buffer.len(),
-                value_ptr: buffer.as_mut_ptr(),
-                result: !0usize
-            };
-            if unsafe { syscall(SysCallIndex::GetEnv, &mut call_record) } {
-                if call_record.result == !0usize {
-                    Err(())
-                } else {
-                    Ok(call_record.result)
-                }
-            } else {
-                Err(())
-            }
-        }).ok().map(|s| {
-            FromInner::from_inner(Buf { inner: s })
-        })
-    }
-}
-
-#[repr(C)]
-pub struct SetEnvSysCall {
-    key_ptr: *const u8,
-    key_len: usize,
-    value_ptr: *const u8,
-    value_len: usize
-}
-
-impl SetEnvSysCall {
-    pub fn perform(key: &OsStr, value: Option<&OsStr>) {
-        let key_buf = &AsInner::as_inner(key).inner;
-        let value_buf = value.map(|v| &AsInner::as_inner(v).inner);
-        let mut call_record = SetEnvSysCall {
-            key_len: key_buf.len(),
-            key_ptr: key_buf.as_ptr(),
-            value_len: value_buf.map(|v| v.len()).unwrap_or(!0usize),
-            value_ptr: value_buf.map(|v| v.as_ptr()).unwrap_or(ptr::null())
-        };
-        unsafe { syscall(SysCallIndex::SetEnv, &mut call_record); }
-    }
-}
-
-pub enum TimeClock {
-    Monotonic = 0,
-    System = 1,
-}
-
-#[repr(C)]
-pub struct TimeSysCall {
-    clock: usize,
-    secs_hi: usize,
-    secs_lo: usize,
-    nanos: usize
-}
-
-impl TimeSysCall {
-    pub fn perform(clock: TimeClock) -> Duration {
-        let mut call_record = TimeSysCall {
-            clock: clock as usize,
-            secs_hi: 0,
-            secs_lo: 0,
-            nanos: 0
-        };
-        if unsafe { syscall(SysCallIndex::Time, &mut call_record) } {
-            Duration::new(
-                ((call_record.secs_hi as u64) << 32) | (call_record.secs_lo as u64),
-                call_record.nanos as u32
-            )
-        } else {
-            panic!("Time system call is not implemented by WebAssembly host");
-        }
-    }
-}
-
-unsafe fn syscall<T>(index: SysCallIndex, data: &mut T) -> bool {
-    #[cfg(feature = "wasm_syscall")]
-    extern {
-        #[no_mangle]
-        fn rust_wasm_syscall(index: usize, data: *mut Void) -> usize;
-    }
-
-    #[cfg(not(feature = "wasm_syscall"))]
-    unsafe fn rust_wasm_syscall(_index: usize, _data: *mut Void) -> usize { 0 }
-
-    rust_wasm_syscall(index as usize, data as *mut T as *mut Void) != 0
-}

src/libstd/sys/wasm/os.rs

@@ -4,7 +4,7 @@ use crate::fmt;
 use crate::io;
 use crate::path::{self, PathBuf};
 use crate::str;
-use crate::sys::{unsupported, Void, ExitSysCall, GetEnvSysCall, SetEnvSysCall};
+use crate::sys::{unsupported, Void};
 
 pub fn errno() -> i32 {
     0
@@ -73,16 +73,16 @@ pub fn env() -> Env {
     panic!("not supported on web assembly")
 }
 
-pub fn getenv(k: &OsStr) -> io::Result<Option<OsString>> {
-    Ok(GetEnvSysCall::perform(k))
+pub fn getenv(_: &OsStr) -> io::Result<Option<OsString>> {
+    Ok(None)
 }
 
-pub fn setenv(k: &OsStr, v: &OsStr) -> io::Result<()> {
-    Ok(SetEnvSysCall::perform(k, Some(v)))
+pub fn setenv(_: &OsStr, _: &OsStr) -> io::Result<()> {
+    Err(io::Error::new(io::ErrorKind::Other, "cannot set env vars on wasm32-unknown-unknown"))
 }
 
-pub fn unsetenv(k: &OsStr) -> io::Result<()> {
-    Ok(SetEnvSysCall::perform(k, None))
+pub fn unsetenv(_: &OsStr) -> io::Result<()> {
+    Err(io::Error::new(io::ErrorKind::Other, "cannot unset env vars on wasm32-unknown-unknown"))
 }
 
 pub fn temp_dir() -> PathBuf {
@@ -94,7 +94,9 @@ pub fn home_dir() -> Option<PathBuf> {
 }
 
 pub fn exit(_code: i32) -> ! {
-    ExitSysCall::perform(_code as isize as usize)
+    unsafe {
+        crate::arch::wasm32::unreachable();
+    }
 }
 
 pub fn getpid() -> u32 {

src/libstd/sys/wasm/stdio.rs

@@ -1,5 +1,4 @@
 use crate::io;
-use crate::sys::{ReadSysCall, WriteSysCall};
 
 pub struct Stdin;
 pub struct Stdout;
@@ -12,8 +11,8 @@ impl Stdin {
 }
 
 impl io::Read for Stdin {
-    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
-        Ok(ReadSysCall::perform(0, buf))
+    fn read(&mut self, _buf: &mut [u8]) -> io::Result<usize> {
+        Ok(0)
     }
 }
 
@@ -25,7 +24,6 @@ impl Stdout {
 
 impl io::Write for Stdout {
     fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
-        WriteSysCall::perform(1, buf);
         Ok(buf.len())
     }
 
@@ -42,7 +40,6 @@ impl Stderr {
 
 impl io::Write for Stderr {
     fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
-        WriteSysCall::perform(2, buf);
         Ok(buf.len())
     }
 
@@ -57,10 +54,6 @@ pub fn is_ebadf(_err: &io::Error) -> bool {
     true
 }
 
-pub fn panic_output() -> Option<impl io::Write> {
-    if cfg!(feature = "wasm_syscall") {
-        Stderr::new().ok()
-    } else {
-        None
-    }
+pub fn panic_output() -> Option<Vec<u8>> {
+    None
 }

src/libstd/sys/wasm/time.rs

@@ -1,5 +1,4 @@
 use crate::time::Duration;
-use crate::sys::{TimeSysCall, TimeClock};
 
 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Debug, Hash)]
 pub struct Instant(Duration);
@@ -11,7 +10,7 @@ pub const UNIX_EPOCH: SystemTime = SystemTime(Duration::from_secs(0));
 
 impl Instant {
     pub fn now() -> Instant {
-        Instant(TimeSysCall::perform(TimeClock::Monotonic))
+        panic!("time not implemented on wasm32-unknown-unknown")
     }
 
     pub const fn zero() -> Instant {
@@ -37,7 +36,7 @@ impl Instant {
 
 impl SystemTime {
     pub fn now() -> SystemTime {
-        SystemTime(TimeSysCall::perform(TimeClock::System))
+        panic!("time not implemented on wasm32-unknown-unknown")
     }
 
     pub fn sub_time(&self, other: &SystemTime)