Try #1657:

.tarpaulin.toml

@@ -1,17 +1,16 @@
 [cranelift_coverage]
 features = "cranelift,singlepass,llvm,test-no-traps,test-cranelift"
+examples = ["early-exit", "engine-jit", "engine-native", "engine-headless", "cross-compilation", "compiler-cranelift", "exported-function", "wasi"]
 release = true
 
 [llvm_coverage]
 features = "cranelift,singlepass,llvm,test-no-traps,test-llvm"
+examples = ["compiler-llvm"]
 release = true
 
 [singlepass_coverage]
 features = "cranelift,singlepass,llvm,test-no-traps,test-singlepass"
-release = true
-
-[feature_a_and_b_coverage]
-features = "feature_a feature_b"
+examples = ["compiler-singlepass"]
 release = true
 
 [report]

CHANGELOG.md

@@ -1,6 +1,7 @@
 # Changelog
 
 ## **[Unreleased]**
+- [#1657](https://github.com/wasmerio/wasmer/pull/1657) Implement `wasm_trap_t` and `wasm_frame_t` for Wasm C API; add examples in Rust and C of exiting early with a host function.
 - [#1645](https://github.com/wasmerio/wasmer/pull/1645) Move the install script to https://github.com/wasmerio/wasmer-install
 
 ## 1.0.0-alpha3 - 2020-09-14

Cargo.toml

@@ -128,6 +128,11 @@ test-no-traps = ["wasmer-wast/test-no-traps"]
 name = "static_and_dynamic_functions"
 harness = false
 
+[[example]]
+name = "early-exit"
+path = "examples/early_exit.rs"
+required-features = ["cranelift"]
+
 [[example]]
 name = "engine-jit"
 path = "examples/engine_jit.rs"

examples/early_exit.rs

@@ -0,0 +1,82 @@
+//! This example shows how the host can terminate execution of Wasm early from
+//! inside a host function called by the Wasm.
+
+use anyhow::bail;
+use std::fmt;
+use wasmer::{imports, wat2wasm, Function, Instance, Module, NativeFunc, RuntimeError, Store};
+use wasmer_compiler_cranelift::Cranelift;
+use wasmer_engine_jit::JIT;
+
+// First we need to create an error type that we'll use to signal the end of execution.
+#[derive(Debug, Clone, Copy)]
+struct ExitCode(u32);
+
+// This type must implement `std::error::Error` so we must also implement `std::fmt::Display` for it.
+impl fmt::Display for ExitCode {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "{}", self.0)
+    }
+}
+
+// And then we implement `std::error::Error`.
+impl std::error::Error for ExitCode {}
+
+// The host function that we'll use to terminate execution.
+fn early_exit() {
+    // This is where it happens.
+    RuntimeError::raise(Box::new(ExitCode(1)));
+}
+
+fn main() -> anyhow::Result<()> {
+    // Let's declare the Wasm module with the text representation.
+    let wasm_bytes = wat2wasm(
+        br#"
+(module
+  (type $run_t (func (param i32 i32) (result i32)))
+  (type $early_exit_t (func (param) (result)))
+  (import "env" "early_exit" (func $early_exit (type $early_exit_t)))
+  (func $run (type $run_t) (param $x i32) (param $y i32) (result i32)
+    (call $early_exit)
+    (i32.add
+        local.get $x
+        local.get $y))
+  (export "run" (func $run)))
+"#,
+    )?;
+
+    let store = Store::new(&JIT::new(&Cranelift::default()).engine());
+    let module = Module::new(&store, wasm_bytes)?;
+
+    let import_object = imports! {
+        "env" => {
+            "early_exit" => Function::new_native(&store, early_exit),
+        }
+    };
+    let instance = Instance::new(&module, &import_object)?;
+
+    // get the `run` function which we'll use as our entrypoint.
+    let run_func: NativeFunc<(i32, i32), i32> =
+        instance.exports.get_native_function("run").unwrap();
+
+    // When we call a function it can either succeed or fail.
+    match run_func.call(1, 7) {
+        Ok(result) => {
+            bail!(
+                "Expected early termination with `ExitCode`, found: {}",
+                result
+            );
+        }
+        // we're expecting it to fail.
+        // we attempt to downcast the error into the error type that we were expecting.
+        Err(e) => match e.downcast::<ExitCode>() {
+            // we found the exit code used to terminate execution.
+            Ok(exit_code) => {
+                println!("Exited early with exit code: {}", exit_code);
+                Ok(())
+            }
+            Err(e) => {
+                bail!("Unknown error `{}` found. expected `ErrorCode`", e);
+            }
+        },
+    }
+}

examples/engine_cross_compilation.rs

@@ -27,16 +27,15 @@ use wasmer_engine_native::Native;
 fn main() -> Result<(), Box<dyn std::error::Error>> {
     // Let's declare the Wasm module with the text representation.
     let wasm_bytes = wat2wasm(
-        r#"
+        br#"
 (module
   (type $sum_t (func (param i32 i32) (result i32)))
   (func $sum_f (type $sum_t) (param $x i32) (param $y i32) (result i32)
     local.get $x
     local.get $y
     i32.add)
   (export "sum" (func $sum_f)))
-"#
-        .as_bytes(),
+"#,
     )?;
 
     // Define a compiler configuration.

examples/wasi.rs

@@ -21,9 +21,9 @@ use wasmer_engine_jit::JIT;
 use wasmer_wasi::WasiState;
 
 fn main() -> Result<(), Box<dyn std::error::Error>> {
-    let wasm_path = format!(
-        "{}/tests/wasi-wast/wasi/unstable/hello.wasm",
-        std::env::var("CARGO_MANIFEST_DIR").unwrap()
+    let wasm_path = concat!(
+        env!("CARGO_MANIFEST_DIR"),
+        "/tests/wasi-wast/wasi/unstable/hello.wasm"
     );
     // Let's declare the Wasm module with the text representation.
     let wasm_bytes = std::fs::read(wasm_path)?;

lib/api/src/lib.rs

@@ -70,8 +70,8 @@ pub use wasmer_compiler::{
 };
 pub use wasmer_compiler::{CpuFeature, Features, Target};
 pub use wasmer_engine::{
-    ChainableNamedResolver, DeserializeError, Engine, InstantiationError, LinkError, NamedResolver,
-    NamedResolverChain, Resolver, RuntimeError, SerializeError,
+    ChainableNamedResolver, DeserializeError, Engine, FrameInfo, InstantiationError, LinkError,
+    NamedResolver, NamedResolverChain, Resolver, RuntimeError, SerializeError,
 };
 pub use wasmer_types::{
     Atomically, Bytes, GlobalInit, LocalFunctionIndex, MemoryView, Pages, ValueType,

lib/c-api/src/wasm_c_api/mod.rs

@@ -17,9 +17,9 @@ use crate::c_try;
 
 use crate::ordered_resolver::OrderedResolver;
 use wasmer::{
-    Engine, ExportType, Extern, ExternType, Function, FunctionType, Global, GlobalType, ImportType,
-    Instance, Memory, MemoryType, Module, Mutability, Pages, RuntimeError, Store, Table, TableType,
-    Val, ValType,
+    Engine, ExportType, Extern, ExternType, FrameInfo, Function, FunctionType, Global, GlobalType,
+    ImportType, Instance, Memory, MemoryType, Module, Mutability, Pages, RuntimeError, Store,
+    Table, TableType, Val, ValType,
 };
 #[cfg(feature = "jit")]
 use wasmer_engine_jit::JIT;
@@ -712,7 +712,13 @@ pub unsafe extern "C" fn wasm_func_new(
             num_rets
         ];
 
-        let _traps = callback(processed_args.as_ptr(), results.as_mut_ptr());
+        let trap = callback(processed_args.as_ptr(), results.as_mut_ptr());
+        dbg!(&trap);
+        if !trap.is_null() {
+            let trap: Box<wasm_trap_t> = Box::from_raw(trap);
+            dbg!("raising trap!");
+            RuntimeError::raise(Box::new(trap.inner));
+        }
         // TODO: do something with `traps`
 
         let processed_results = results
@@ -783,7 +789,7 @@ pub unsafe extern "C" fn wasm_func_call(
     func: &wasm_func_t,
     args: *const wasm_val_t,
     results: *mut wasm_val_t,
-) -> Option<NonNull<wasm_trap_t>> {
+) -> Option<Box<wasm_trap_t>> {
     let num_params = func.inner.ty().params().len();
     let params: Vec<Val> = (0..num_params)
         .map(|i| (&(*args.add(i))).try_into())
@@ -798,7 +804,7 @@ pub unsafe extern "C" fn wasm_func_call(
             }
             None
         }
-        Err(e) => Some(NonNull::new_unchecked(Box::into_raw(Box::new(e)) as _)),
+        Err(e) => Some(Box::new(e.into())),
     }
 }
 
@@ -1150,31 +1156,48 @@ pub struct wasm_ref_t;
 
 // opaque type which is a `RuntimeError`
 #[repr(C)]
-pub struct wasm_trap_t {}
+pub struct wasm_trap_t {
+    inner: RuntimeError,
+}
 
-#[no_mangle]
-pub unsafe extern "C" fn wasm_trap_delete(trap: Option<NonNull<wasm_trap_t>>) {
-    if let Some(t_inner) = trap {
-        let _ = Box::from_raw(t_inner.cast::<RuntimeError>().as_ptr());
+impl From<RuntimeError> for wasm_trap_t {
+    fn from(other: RuntimeError) -> Self {
+        Self { inner: other }
     }
 }
 
 #[no_mangle]
-pub unsafe extern "C" fn wasm_trap_message(
-    trap: *const wasm_trap_t,
-    out_ptr: *mut wasm_byte_vec_t,
-) {
-    let re = &*(trap as *const RuntimeError);
-    // this code assumes no nul bytes appear in the message
-    let mut message = format!("{}\0", re);
-    message.shrink_to_fit();
+pub unsafe extern "C" fn wasm_trap_new(
+    _store: &mut wasm_store_t,
+    message: &wasm_message_t,
+) -> Option<Box<wasm_trap_t>> {
+    let message_bytes: &[u8] = message.into_slice()?;
+    let message_str = c_try!(std::str::from_utf8(message_bytes));
+    let runtime_error = RuntimeError::new(message_str);
+    let trap = runtime_error.into();
+
+    Some(Box::new(trap))
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn wasm_trap_delete(_trap: Option<Box<wasm_trap_t>>) {}
+
+#[no_mangle]
+pub unsafe extern "C" fn wasm_trap_message(trap: &wasm_trap_t, out_ptr: &mut wasm_byte_vec_t) {
+    let message = trap.inner.message();
+    out_ptr.size = message.len();
+    // TODO: make helper function for converting `Vec<T>` into owned `wasm_T_vec_t`
+    let mut dupe_data: Box<[u8]> = message.into_bytes().into_boxed_slice();
+    out_ptr.data = dupe_data.as_mut_ptr();
+    mem::forget(dupe_data);
+}
 
-    // TODO use `String::into_raw_parts` when it gets stabilized
-    (*out_ptr).size = message.as_bytes().len();
-    (*out_ptr).data = message.as_mut_ptr();
-    mem::forget(message);
+#[no_mangle]
+pub unsafe extern "C" fn wasm_trap_origin(trap: &wasm_trap_t) -> Option<Box<wasm_frame_t>> {
+    trap.inner.trace().first().map(Into::into).map(Box::new)
 }
 
+// TODO: old comment, rm after finish implementation
 // in trap/RuntimeError we need to store
 // 1. message
 // 2. origin (frame); frame contains:
@@ -1183,11 +1206,19 @@ pub unsafe extern "C" fn wasm_trap_message(
 //    3. module offset
 //    4. which instance this was apart of
 
-/*#[no_mangle]
-pub unsafe extern "C" fn wasm_trap_trace(trap: *const wasm_trap_t, out_ptr: *mut wasm_frame_vec_t) {
-    let re = &*(trap as *const RuntimeError);
-    todo!()
-}*/
+#[no_mangle]
+pub unsafe extern "C" fn wasm_trap_trace(trap: &wasm_trap_t, out_ptr: &mut wasm_frame_vec_t) {
+    let frames = trap.inner.trace();
+    out_ptr.size = frames.len();
+    // TODO: make helper function for converting `Vec<T>` into owned `wasm_T_vec_t`
+    let mut dupe_data: Box<[wasm_frame_t]> = frames
+        .iter()
+        .map(Into::into)
+        .collect::<Vec<wasm_frame_t>>()
+        .into_boxed_slice();
+    out_ptr.data = dupe_data.as_mut_ptr();
+    mem::forget(dupe_data);
+}
 
 #[repr(C)]
 pub struct wasm_extern_t {
@@ -1543,9 +1574,52 @@ pub unsafe extern "C" fn wasm_functype_results(ft: &wasm_functype_t) -> *const w
     out as *const _
 }
 
-#[derive(Debug)]
+#[derive(Debug, Clone)]
 #[repr(C)]
-pub struct wasm_frame_t {}
+pub struct wasm_frame_t {
+    info: FrameInfo,
+}
+
+impl<'a> From<&'a FrameInfo> for wasm_frame_t {
+    fn from(other: &'a FrameInfo) -> Self {
+        other.clone().into()
+    }
+}
+
+impl From<FrameInfo> for wasm_frame_t {
+    fn from(other: FrameInfo) -> Self {
+        Self { info: other }
+    }
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn wasm_frame_copy(frame: &wasm_frame_t) -> Box<wasm_frame_t> {
+    Box::new(frame.clone())
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn wasm_frame_delete(_frame: Option<Box<wasm_frame_t>>) {}
+
+#[no_mangle]
+pub unsafe extern "C" fn wasm_frame_instance(frame: &wasm_frame_t) -> *const wasm_instance_t {
+    //todo!("wasm_frame_instance")
+    std::ptr::null()
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn wasm_frame_func_index(frame: &wasm_frame_t) -> u32 {
+    frame.info.func_index()
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn wasm_frame_func_offset(frame: &wasm_frame_t) -> usize {
+    frame.info.func_offset()
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn wasm_frame_module_offset(frame: &wasm_frame_t) -> usize {
+    frame.info.module_offset()
+}
 
 wasm_declare_vec!(frame);
 
@@ -1769,6 +1843,9 @@ pub unsafe extern "C" fn wasm_tabletype_as_externtype(
 #[allow(non_camel_case_types)]
 type wasm_name_t = wasm_byte_vec_t;
 
+#[allow(non_camel_case_types)]
+type wasm_message_t = wasm_byte_vec_t;
+
 #[repr(C)]
 #[allow(non_camel_case_types)]
 pub struct wasm_exporttype_t {